Seroprevalence and associated risk factors of chikungunya, dengue, and Zika in eight districts in Tanzania

Open AccessPublished:August 21, 2021DOI:https://doi.org/10.1016/j.ijid.2021.08.040

      Abstract

      Background: This study was conducted to determine the seroprevalence and risk factors of chikungunya (CHIKV), dengue (DENV), and Zika (ZIKV) viruses in Tanzania.
      Methods: The study covered the districts of Buhigwe, Kalambo, Kilindi, Kinondoni, Kondoa, Kyela, Mvomero, and Ukerewe in Tanzania. Blood samples were collected from individuals recruited from households and healthcare facilities. An ELISA was used to screen for immunoglobulin G antibodies against CHIKV, DENV, and ZIKV.
      Results: A total of 1818 participants (median age 34 years) were recruited. The overall CHIKV, DENV, and ZIKV seroprevalence rates were 28.0%, 16.1%, and 6.8%, respectively. CHIKV prevalence was highest in Buhigwe (46.8%), DENV in Kinondoni (43.8%), and ZIKV in Ukerewe (10.6%) and Mvomero (10.6%). Increasing age and frequent mosquito bites were significantly associated with CHIKV and DENV seropositivity (P < 0.05). Having piped water or the presence of stagnant water around the home (P < 0.01) were associated with higher odds of DENV seropositivity. Fever was significantly associated with increased odds of CHIKV seropositivity (P < 0.001). Visiting mines had higher odds of ZIKV seropositivity (P < 0.05).
      Conclusions: These findings indicate that DENV, CHIKV, and ZIKV are circulating in diverse ecological zones of Tanzania. There is a need to strengthen the control of mosquito-borne viral diseases in Tanzania.

      KEYWORDS

      Introduction

      Globally, arthropod-borne viral diseases account for 17% of all human infectious diseases (
      • Jones KE
      • Patel NG
      • Levy MA
      • Storeygard A
      • Balk D
      • Gittleman JL
      • et al.
      Global trends in emerging infectious diseases.
      ;
      • Kading R
      • Brault AC
      • Beckham JD.
      Global perspectives on arbovirus outbreaks: a 2020 snapshot.
      ). Of the arboviral diseases, mosquito-borne diseases are the most important, affecting millions of people, and comprise an important proportion of emerging and re-emerging human pathogens. Dengue, yellow fever, Japanese encephalitis, chikungunya, and Rift Valley fever have been described to contribute highly to disability-adjusted life years (
      • Labeaud D
      • Bashir F
      • King CH.
      Measuring the burden of arboviral diseases: The spectrum of morbidity and mortality from four prevalent infections.
      ;
      • Stanaway JD
      • Shepard DS
      • Undurraga EA
      • Halasa YA
      • Coffeng LE
      • Brady OJ.
      • et al.
      The global burden of dengue: an analysis from the Global Burden of Disease study 2013.
      ;
      • Zeng W
      • Halasa-Rappel YA
      • Durand L
      • Coudeville L
      • Shepard DS
      Impact of a nonfatal dengue episode on disability-adjusted life years: a systematic analysis.
      ). Global human population growth, unplanned settlements, international travel, and climate variability/change are among the factors that contribute to the expansion of the spread of arboviral diseases (
      • Gould EA
      • Higgs S.
      Impact of climate change and other factors on emerging arbovirus diseases. Trans.
      ;
      • Gubler DJ.
      Dengue, urbanization and globalization: the unholy trinity of the 21st century.
      ;
      • Lambrechts L
      • Scott TW
      • Gubler DJ.
      Consequences of the expanding global distribution of Aedes albopictus for dengue virus transmission.
      ;
      • Braack L
      • Gouveia de Almeida AP
      • Cornel AJ
      • Swanepoel R
      • de Jager C.
      Mosquito-borne arboviruses of African origin: review of key viruses and vectors.
      ). This increases the risk of mosquito-borne viral infections through cycles involving human–human and human–peri-domestic Aedes mosquito transmission (
      • Braack L
      • Gouveia de Almeida AP
      • Cornel AJ
      • Swanepoel R
      • de Jager C.
      Mosquito-borne arboviruses of African origin: review of key viruses and vectors.
      ;
      • Gaye A
      • Wang E
      • Vasilakis N
      • Guzman H
      • Diallo D
      • Talla C.
      • et al.
      Potential for sylvatic and urban Aedes mosquitoes from Senegal to transmit the new emerging dengue serotypes 1, 3 and 4 in West Africa.
      ).
      Periodic outbreaks related to mosquito-borne viral infections are common in sub-Saharan Africa (SSA) and include Rift Valley fever, dengue, chikungunya, Zika, and yellow fever (
      • Braack L
      • Gouveia de Almeida AP
      • Cornel AJ
      • Swanepoel R
      • de Jager C.
      Mosquito-borne arboviruses of African origin: review of key viruses and vectors.
      ). Recent dengue virus (DENV) outbreaks have been reported in Tanzania (
      • Vairo F
      • Nicastri E
      • Meschi S
      • Schepisi MS
      • Paglia MG
      • Bevilacqua N.
      • et al.
      Seroprevalence of dengue infection: a cross-sectional survey in mainland Tanzania and on Pemba Island, Zanzibar.
      ;
      • Ward T
      • Samuel M
      • Maoz D
      • Runge-Ranzinger S
      • Boyce R
      • Toledo J.
      • et al.
      Dengue data and surveillance in Tanzania: a systematic literature review.
      ;
      • Chipwaza B
      • Sumaye RD
      • Weisser M
      • Gingo W
      • Kim-Wah Y
      • Amrun SN.
      • et al.
      Occurrence of 4 Dengue virus serotypes and chikungunya virus in Kilombero Valley, Tanzania, during the dengue outbreak in 2018.
      ), Mozambique (
      • Mugabe VA
      • Ali S
      • Chelene I
      • Monteiro VO
      • Guiliche O
      • Muianga AF.
      • et al.
      Evidence for chikungunya and dengue transmission in Quelimane, Mozambique: Results from an investigation of a potential outbreak of chikungunya virus.
      ), Ghana (
      • Amoako N
      • Duodu S
      • Dennis FE
      • Bonney JH
      • Asante KP.
      • Ameh J.
      • et al.
      Detection of dengue virus among children with suspected malaria.
      ), Sudan (
      • Elaagip A
      • Alsedig K
      • Altahir O
      • Ageep T
      • Ahmed A
      • Siam H.
      • et al.
      Seroprevalence and associated entomological and socioeconomic risk factors of Dengue fever in Kassala State, eastern Sudan.
      ), Benin, Cote d'Ivoire, and Mauritius (

      WHO. Weekly Bulletin on Outbreaks and other Emergencies. Week 27: 1-7 July 2019. https://apps.who.int/iris/bitstream/handle/10665/325777/OEW27-0107072019.pdf

      ). Outbreaks of chikungunya virus (CHIKV) have been reported in Kenya (
      • Kariuki Njenga M
      • Nderitu L
      • Ledermann JP
      • Ndirangu A
      • Logue CH
      • Kelly CHL.
      • et al.
      Tracking epidemic Chikungunya virus into the Indian Ocean from East Africa.
      ), the Republic of Congo (
      • Vairo F
      • Coussoud-Mavoungou MPA
      • Ntoumi F
      • Castilletti C
      • Kitembo L
      • Haider N.
      • et al.
      Chikungunya outbreak in the Republic of the Congo, 2019 - epidemiological, virological and entomological findings of a south-north multidisciplinary taskforce investigation.
      ), and the Reunion Islands (
      • Vazeille M
      • Moutailler S
      • Coudrier D
      • Rousseaux C
      • Khun H
      • Huerre M.
      • et al.
      Two chikungunya isolates from the outbreak of La Reunion (Indian Ocean) exhibit different patterns of infection in the mosquito, Aedes albopictus.
      ). Zika virus (ZIKV) infections have been reported in Cape Verde (
      • Kindhauser MK
      • Allen T
      • Frank V
      • Santhana R
      • Dye C.
      Zika: the origin and spread of a mosquito-borne virus.
      ;
      • Lourenço J
      • de Lourdes Monteiro M
      • Valdez T
      • Monteiro Rodrigues J
      • Pybus O
      • Rodrigues Faria N
      Epidemiology of the Zika Virus Outbreak in the Cabo Verde Islands, West Africa.
      ), Guinea Bissau (
      • Gulland A
      Continued spread of Zika raises many research questions, WHO says.
      ), Mozambique (
      • Gudo ES
      • Falk KI
      • Ali S
      • Muianga AF
      • Monteiro V
      • Cliff J.
      A historic report of Zika in Mozambique: implications for assessing current risk.
      ), and Angola (
      • Hill SC
      • Vasconcelos J
      • Neto Z
      • Jandondo D
      • Zé-Zé L
      • Aguiar R.S.
      • et al.
      Emergence of the Asian lineage of Zika virus in Angola: an outbreak investigation.
      ). Although the acute stages of arboviral infections most often cause a broad spectrum of clinical manifestations, ranging from asymptomatic to severe undifferentiated fever (
      • Forshey BM
      • Guevara C
      • Alberto Laguna-Torress V
      • Cespedes M
      • Vargas J.
      • et al.
      Arboviral Etiologies of Acute Febrile Illnesses in Western South America, 2000–2007.
      ;
      • Labeaud D
      • Bashir F
      • King CH.
      Measuring the burden of arboviral diseases: The spectrum of morbidity and mortality from four prevalent infections.
      ), they are also causes of fever that is often considered to be malaria by clinicians, especially in areas with inadequate laboratory capacities (
      • Crump JA
      • Morrissey AB
      • Nicholson WL
      • Massung RF
      • Stoddard RA
      • Galloway RL.
      • et al.
      Etiology of severe non-malaria febrile illness in northern Tanzania: a prospective cohort study.
      ;
      • Ayorinde AF
      • Oyeyiga AM
      • Nosegbe NO
      • Folarin OA.
      A survey of malaria and some arboviral infections among suspected febrile patients visiting a health centre in Simawa.
      ).
      Despite the evidence that arboviral diseases such as dengue and chikungunya contribute substantially to morbidity in Tanzania, there are only a few isolated studies that have documented their burden, drivers, and vulnerability (
      • Vairo F
      • Nicastri E
      • Meschi S
      • Schepisi MS
      • Paglia MG
      • Bevilacqua N.
      • et al.
      Seroprevalence of dengue infection: a cross-sectional survey in mainland Tanzania and on Pemba Island, Zanzibar.
      ;
      • Kinimi E
      • Shayo M
      • Bisimwa P
      • Angwenyi S
      • Kasanga C
      • Weyer J.
      • et al.
      Evidence of chikungunya virus infection among febrile patients seeking healthcare in selected districts of Tanzania.
      ;
      • Budodo RM
      • Horumpende PG
      • Mkumbaye SI
      • Mmbaga BT
      • Mwakapuja RS
      • Chilongola JO.
      Serological evidence of exposure to Rift Valley, dengue and chikungunya viruses among agropastoral communities in Manyara and Morogoro regions in Tanzania: A community survey.
      ). Most of these studies have been facility-based studies, and little evidence has been based on population-based studies. This means that their distribution in the country remains uncertain. The objective of this study was, therefore, to determine the seroprevalence and risk factors of chikungunya, dengue, and Zika in diverse ecological zones of Tanzania.

      Materials and methods

       Study sites and design

      This cross-sectional study was performed between April and November 2018. A multistage cluster design was utilized to select the study sites. The country was first divided into five distinct ecological zones based on vegetation and land cover, normalized difference vegetation index, rainfall and number of wet days per month, and elevation. Zone 1 comprised the western parts of Tanzania, with tropical forest, a unimodal rainfall pattern, and altitude <2300 m above sea level. Zone 2 included the Southern Highlands districts, with tropical forest, a bimodal rainfall pattern, and elevation >2300 m. Zone 3 comprised the north-eastern part of the country, lying along the Indian Ocean to 1800 m above sea level. Zone 4 covered the central part of the country, characterized by wet savannah with bimodal rainfall (1400 mm) and semi-arid areas characterized by a short wet season (with rainfall of 400–800 mm per year). Zone 5 comprised the Lake Victoria basin, characterized by a bimodal rainfall pattern (900–1800 mm) with a moderate warm climate.
      Buhigwe and Kalambo districts were selected to represent the Western zone and Kyela district the Southern Highland zone, while Kilindi and Kinondoni districts represented the North-eastern zone. Mvomero and Kondoa districts were selected to represent the Central zone, while Ukerewe district represented the Lake Victoria zone (Fig. 1). Details of the study sites have been described elsewhere (Rugarabamu et al., 2021).
      Fig. 1
      Fig. 1Map of Tanzania showing the ecological zones and study districts.

       Sample size and sampling

      A recent review on dengue prevalence in Africa reported IgG prevalence of 15.6% (range 9.9–22.2%) for healthy populations and 24.8% (range 13.8–37.8%) for populations presenting with fever (
      • Simo FBN
      • Bigna JJ
      • Kenmoe S
      • Ndangang MS
      • Temfack E
      • Moundipa PF.
      • et al.
      Dengue virus infection in people residing in Africa: a systematic review and meta-analysis of prevalence studies.
      ). This study planned to collect data from both the household and health facility settings; thus, based on the ecology of the zones, different levels of expected prevalence (P) were assumed in order to obtain the needed sample sizes. For zones 1, 2, and 4, the average of the healthy and fever populations (P = 20.1%) was used; for zone 3, the average of the upper ranges (P = 30%) was used, since it includes a district (Kinondoni) within a large city. The district in zone 5 is an island and was assumed to have a low prevalence, hence the lower prevalence (P = 9.9%) was used. The design effect of 1.5 was used to account for any clustering effect between the districts within the same zone. With the desired absolute precision of 5% and confidence level of 95%, the minimum estimated sample size was 1792 individuals, with the following breakdown: zone 1: n = 454 (Buhigwe = 255; Kalambo = 198); zone 2: Kyela (258); zone 3: n = 461 (Kilindi = 226; Kinondoni = 235); zone 4: n = 395 (Kondoa = 203; Mvomero = 192); and zone 5: Ukerewe (224). A contingency of 10% was considered to account for non-responses, refusal, and/or missing values. The zonal sample was split using probability proportional to the size of the district population to obtain district-specific sample sizes. The study district population densities per square kilometre for Buhigwe, Kalambo, Kilindi, Kinondoni, Kondoa, Kyela, Mvomero, and Ukerewe were 168.8, 15.98, 37.0, 3300, 46.6, 755.9, 47.05, and 283.02, respectively.
      Three wards were selected from each district, and three villages were selected from each of the three wards. A minimum of 14 participants was targeted for each village or health facility. At the village level, four to five households were randomly selected based on the sampling frame obtained from the village office. Once selected, all eligible members of the household were recruited into the study. In the healthcare facility setting, one hospital, two health centres, and four dispensaries were selected in each district. In each facility, the study subjects were recruited on a first-come-first-included basis until the targeted sample size was achieved. Children <9 months old were excluded based on the fact that maternal antibodies acquired through transplacental route and during breastfeeding are likely to lead to false-positive results (
      • Watanaveeradej V
      • Endy TP
      • Samakoses R
      • Kerdpanich A
      • Simasathien S
      • Polprasert N
      • et al.
      Transplacentally transferred maternal-infant antibodies to dengue virus.
      ).

       Sociodemographic and clinical data

      A semi-structured questionnaire installed on smartphones with a digital data collection tool (AfyaData) (
      • Karimuribo ED
      • Mutagahywa E
      • Sindato C
      • Mboera L
      • Mwabukusi M
      • Kariuki Njenga M
      • et al.
      A Smartphone App (AfyaData) for innovative one health disease surveillance from community to national levels in Africa: Intervention in disease surveillance.
      ) was used to collect sociodemographic and epidemiological data. The data included age, education level, occupation, history of fever, knowledge about mosquito-borne diseases, household water source, and water storage. All study participants were examined for clinical manifestations suggestive of fever and associated disease conditions. Body temperature was recorded using a digital thermometer.

       Laboratory analysis

      From each participant, about 3–5 ml of blood was collected into a plain vacutainer tube and allowed to clot at room temperature. Thereafter, serum was separated by centrifugation at 3000 rpm for 10 minutes. Serum aliquots of 0.5–1 ml were placed into sterile cryovials labelled with a unique identification code and transported in liquid nitrogen (−196°C) to the laboratory, where they were stored in an ultralow temperature freezer (−80°C) until analysed. Each serum sample was screened in duplicate for human immunoglobulin G (IgG) antibodies against CHIKV, DENV, and ZIKV using EUROIMMUN indirect ELISA test kits (Medizinische Labordiagnostika AG, Lübeck, Germany). The average value of a sample was classified as positive for IgG when the ratio of optical density (OD) of the control or sample over that of the calibrator was ≥1.1, negative when the ratio was <0.8, and borderline when the ratio was ≥0.8 to <1.1. The sensitivity and specificity of the ELISA test kits used were reported to be 98.5% and 95.7% for anti-dengue IgG, 96.8% and 98.0% for anti-chikungunya IgG, and 99.2% and 98.0% for anti-Zika IgG, respectively.

       Statistical analysis

      Data were imported into Microsoft Excel 2016 (Microsoft Corp, Redmond, WA, USA), cleaned, and organized for analysis. Data were analysed using Stata version 13 (Stata Corp., College Station, TX, USA). Descriptive statistics and frequency tables were used to summarize the data. The Chi-square test was used to determine the association between categorical variables and seroprevalence of CHIKV, DENV, and ZIKV or multiple infections. The variables associated with seroprevalence were subjected to logistic regression analysis to identify significant risk factors for seropositivity. The magnitude of association was measured using the odds ratio (OR) and 95% confidence interval (CI). A variable with a probability value (P-value) less than 0.05 was considered statistically significant.

      Results

       Seroprevalence of DENV, CHIKV, and ZIKV

      A total of 1818 participants were involved in the study. They were recruited from 24 wards, 72 villages, and 56 healthcare facilities. Of the facilities involved, eight were hospitals, 16 were health centres, and 32 were dispensaries. The median age was 34 years, with an interquartile range (IQR) of 23–47 years. The overall seroprevalence rates of CHIKV, DENV, and ZIKV were 28.0%, 16.1%, and 6.8%, respectively. The highest seroprevalence rates for CHIKV (43.4%) and ZIKV (10.6%) IgG antibodies were in the Lake Victoria zone. The highest seroprevalence of DENV IgG antibodies was in the North-eastern zone (28.6%) (Table 1). The mean age of CHIKV, DENV, and ZIKV positive individuals was 40, 39, and 38 years, respectively. District-wise, the highest seroprevalence of CHIKV was in Buhigwe (46.8%), of DENV was in Kinondoni (43.8%), and of ZIKV was in Ukerewe (10.6%) (Fig. 2).
      Table 1Seroprevalence of immunoglobulin G antibodies (IgG) specific to dengue, chikungunya, and Zika viruses by sociodemographic characteristics, ecological zones, and exposure risk factors
      VariableCategoryNumber testedDengueChikungunyaZika
      Number IgG-positive (%)Number IgG-positive (%)Number IgG-positive (%)
      SexFemale989151 (15.3)273 (27.7)59 (5.9)
      Male829141 (17.1)236 (28.6)62 (7.5)
      Age (years)<2864271 (11.1)128 (19.9)39 (6.1)
      28–42607109 (17.9)179 (29.5)42 (6.9)
      >42569112 (19.7)202 (35.5)43 (7.6)
      EducationPrimary1135183 (16.1)327 (28.8)73 (6.4)
      Secondary21949 (22.4)53 (31.9)16 (7.3)
      Post-secondary535 (9.4)10 (18.9)6 (11.3)
      None41155 (13.4)119 (28.9)29 (7.1)
      OccupationFarming1067148 (13.9)343 (32.2)82 (7.7)
      Trading530111 (20.9)127 (23.9)28 (5.3)
      Employed8718 (20.7)20 (22.9)8 (9.2)
      Student13415 (11.2)19 (6.7)6 (4.5)
      Ecological zoneWestern zone46144 (9.5)171 (37.1)26 (5.6)
      North-eastern465133 (28.6)105 (22.6)25 (5.4)
      Central40155 (13.7)62 (15.5)26 (6.5)
      Southern Highlands26531 (11.7)73 (27.6)23 (8.7)
      Lake Victoria22629 (12.8)98 (43.4)24 (10.6)
      Sampling settingFacility833117 (14.1)243 (29.2)65 (7.8)
      Household985175 (17.8)266 (27.0)59 (5.9)
      FeverYes719 (12.7)34 (47.9)10 (14.1)
      No174762 (3.6)475 (27.2)114 (6.5)
      Mosquito biteYes1205197 (16.4)358 (29.7)78 (6.5)
      No61394 (15.3)151 (24.6)46 (7.5)
      Stagnant waterYes14645 (30.8)45 (30.8)12 (8.2)
      No1672247 (14.8)464 (27.8)112 (6.7)
      Piped waterYes523113 (21.6)155 (29.6)35 (6.7)
      No1295179 (13.8)354 (27.3)89 (6.9)
      Mosquito net useYes1140197 (17.3360 (31.6)71 (6.2)
      No67895 (14.0)149 (21.9)53 (7.8)
      Visiting minesYes354 (11.4)8 (22.9)6 (17.1)
      No1783288 (16.2)501 (28.1)118 (6.6)
      Fig. 2
      Fig. 2Seroprevalence of immunoglobulin G (IgG) antibodies specific for dengue virus (DENV), chikungunya virus (CHIKV), and Zika virus (ZIKV) by district.
      Having a secondary education (P = 0.02), water bodies around the home, and piped water at home were significantly associated with DENV seropositivity. Fever was significantly associated with CHIKV (P < 0.001) and ZIKV (P = 0.02) seropositivity. Having visited mines was significantly associated with ZIKV seropositivity (P < 0.04). Increasing participant age and experience of frequent mosquito bites were significantly associated with DENV and CHIKV seropositivity, with individuals aged 28–42 and >42 years having been more exposed than those aged <28 years (Table 2).
      Table 2Prevalence of IgG antibodies to multiple arboviruses by sociodemographic characteristics, ecological zones, and exposure risk factors
      Exposure risk factorCategoryNumber testedDENV+CHIKV+ZIKVDENV+CHIKVCHIKV+ZIKVCross-reactivity
      Number IgG-positive (%)Number IgG-positive (%)Number IgG-positive (%)Number IgG-positive (%)
      SexFemale9855 (0.5)59 (5.9)18 (1.8)8 (0.9)
      Male82510 (1.2)52 (6.3)12 (1.5)8 (0.9)
      Age (years)<286421 (0.2)15 (2.3)8 (1.3)6 (0.9)
      28–426075 (0.8)47 (7.7)11 (1.8)7 (1.2)
      >425699 (1.6)49 (8.6)11 (1.9)3 (0.5)
      EducationPrimary11359 (0.8)73 (6.4)20 (1.8)9 (0.8)
      Secondary2192 (0.9)14 (6.4)3 (1.4)2 (0.9)
      Post-secondary530 (0.0)1 (1.9)2 (3.8)1 (1.9)
      None4114 (0.9)23 (5.6)5 (1.2)4 (0.9)
      OccupationFarming106711 (1.0)64 (5.9)21 (1.9)9 (0.8)
      Trading5303 (0.6)40 (7.6)4 (0.8)6 (1.1)
      Employed870 (0.0)5 (5.8)4 (4.6)1 (1.2)
      Student1341 (0.8)2 (1.5)1 (0.8)0 (0.0)
      Ecological zoneWestern4612 (0.4)25 (0.4)8 (1.7)2 (0.4)
      North-eastern4651 (0.2)36 (7.7)3 (0.7)2 (0.4)
      Central4015 (1.3)20 (4.9)6 (1.5)6 (1.5)
      Southern2652 (0.8)16 (6.0)3 (1.1)4 (1.5)
      Lake Victoria2265 (2.2)14 (6.2)10 (4.4)2 (0.9)
      Sampling settingFacility8336 (0.7)47 (5.6)20 (2.4)6 (0.7)
      Household9859 (0.9)64 (6.5)10 (1.0)10 (1.0)
      FeverYes712 (2.8)5 (7.0)1 (1.4)0 (0.0)
      No174713 (0.7)106 (6.1)29 (1.7)16 (0.9)
      Mosquito net useYes114012 (1.1)85 (7.5)18 (1.6)10 (0.9)
      No6783 (0.4)26 (3.8)12 (1.8)6 (0.9)
      Mosquito biteYes120512 (0.2)82 (6.7)20 (1.7)10 (0.8)
      No6133 (0.5)29 (1.5)10 (1.6)6 (0.9)
      Stagnant waterYes1463 (2.1)16 (10.9)3 (2.1)2 (1.4)
      No167212 (0.7)95 (5.6)27 (1.6)14 (0.8)
      Piped waterYes5235 (0.9)62 (11.9)9 (1.7)7 (1.3)
      No129510 (0.8)49 (3.8)21 (1.6)9 (0.7)
      Visiting minesYes350 (0.0)2 (5.7)2 (5.7)0 (0.0)
      No178315 (0.8)109 (6.1)28 (1.6)16 (0.9)
      CHIKV, chikungunya virus; DENV, dengue virus; ZIKV, Zika virus.

       Seroprevalence of co-circulation of CHIKV, DENV, and ZIKV

      Of the 1818 serum samples tested, 80 (4.4%) were positive for both DENV and CHIKV IgG antibodies, 14 (0.8%) for CHIKV and ZIKV IgG antibodies, 16 (0.88%) for DENV and ZIKV IgG antibodies, and 16 (0.99%) for DENV and CHIKV and ZIKV IgG antibodies (Fig. 3). The prevalence of IgG antibodies for CHIKV+ZIKV exposure was highest in Ukerewe (4.0%; n = 224), while the highest prevalence of DENV+CHIKV antibodies was in Kinondoni (15.0%; n = 235). The overall prevalence of IgG antibodies specific to at least one pathogen (DENV or CHIKV or ZIKV) was 41% (n = 747), and it was highest in Kinondoni (59.0%; n = 255), followed by Ukerewe (51%, n = 224) and Buhigwe (50%, n = 255) (Fig. 4). There was a significant difference in CHIKV+ZIKV seropositivity between ecological zones (P = 0.01), with the highest seroprevalence in the Lake Victoria zone (4.0%; n = 224). Individuals aged >42 years were more significantly associated with increased DENV+CHIKV (8.6%; P < 0.05) and DENV+CHIKV+ZIKV (1.6%; P = 0.02) seropositivity than their younger counterparts. Occupation (P = 0.04) and sampling setting (P = 0.03) were significantly associated with CHIKV+ZIKV seropositivity. The highest seroprevalence was among those employed (4.6%) and those sampled from health facility settings (2.4%). Having piped water (P < 0.001) and the presence of stagnant water around the home (P = 0.02) were significantly associated with DENV+CHIKV seropositivity.
      Fig. 3
      Fig. 3Number and percentage (%) of samples positive for immunoglobulin G (IgG) antibodies to single and multiple exposures of dengue virus, chikungunya virus, and Zika virus.
      Fig. 4
      Fig. 4Immunoglobulin G (IgG) seropositivity for multiple exposures and cross-reactivity of dengue, chikungunya and Zika viruses by district.

       Potential risk factors for DENV, CHIKV, and ZIKV seropositivity

      Potential risk factors varied between the three infections, and the magnitude of the risk was found to differ significantly among the ecological zones. Age was an important factor for DENV and CHIKV seropositivity, with older age (>28 years) indicating a higher risk than in the younger population (P < 0.001). Experiencing frequent mosquito bites (P < 0.01), having piped water (P < 0.01), and the presence of stagnant water around the home (P < 0.01) were significantly associated with higher odds of DENV seropositivity, but were not important factors for CHIKV or ZIKV (Table 3). Having a fever was significantly associated with increased odds of CHIKV seropositivity (P < 0.001), while the use of mosquito nets was associated with higher odds for CHIKV. On the other hand, visiting mines had higher odds of ZIKV seropositivity (P < 0.05). In the ecological zones, the highest risks were observed for CHIKV seropositivity, with over three-fold differences in the Lake Victoria and Western zones compared to the Central zone. The North-eastern zone had higher odds of DENV seropositivity rates (P < 0.001) compared to the other ecological zones. A higher risk of ZIKV was identified in the Lake Victoria zone compared to the other ecological zones. However, these results were not statistically significant. Although with no statistical significance, the risk for ZIKV was estimated to be higher in the Lake Victoria zone than in the other ecological zones (Table 3).
      Table 3Risk factors associated with dengue, chikungunya, and Zika IgG seropositivity in the univariate and multivariable logistic regression models
      Exposure risk factorCategoryDengueChikungunyaZika
      UnivariateMultivariateUnivariateMultivariableUnivariateMultivariable
      OR (95% CI)OR (95% CI)OR (95% CI)OR (95% CI)OR (95% CI)OR (95% CI)
      Age (years)<28Ref.Ref.Ref.Ref.Ref.-
      28–421.8 (1.3−2.4)***1.9 (1.2−2.7)***1.7 (1.3−2.2)***1.6 (1.2−2.1)**1.3 (0.8−1.9)-
      >421.9 (1.4−2.7)***2.3 (1.6−3.4)***2.2 (1.7−2.9)***2.1 (1.6−2.8)***1.2 (0.7−1.8)-
      OccupationEmployedRef.Ref.Ref.-Ref.-
      Farmingo.6 (0.4−1.1)-1.6 (0.9−2.7)-0.8 (0.4−1.9)-
      Trading1.0 (0.6−1.8)-1.1 (0.6−1.9)-0.6 (0.3−1.3)-
      Student0.5 (0.2–1.0)-0.6 (0.3−1.1)-0.5 (0.2−1.4)-
      EducationPrimary1.2 (0.9−1.7)1.0 (0.7−1.4)0.9 (0.8−1.3)-0.9 (0.6−1.4)-
      Secondary1.9 (1.2−2.9)**1.4 (0.9−2.3)0.8 (0.5−1.1)-1.0 (0.5−1.9)-
      Post-secondary0.7 (0.2−1.6)0.4 (0.1–1.0)0.6 (0.3−1.1)-1.7 (0.6−4.0)-
      NoneRef.Ref.Ref.-Ref.-
      Ecological zoneCentralRef.Ref.Ref.Ref.Ref.Ref.
      Western0.6 (0.4−1.0)0.7 (0.5−1.1)3.2 (2.3−4.5)***3.3 (2.4−4.7)***0.9 (0.5−1.5)0.9 (0.5−1.6)
      North-eastern2.5 (1.8−3.6)***2.2 (1.5−3.2)***1.6 (1.1−2.3)**1.7 (1.2−2.4)**0.8 (0.5−1.5)0.8 (0.5−1.6)
      Southern Highlands0.8 (0.5−1.3)0.9 (0.6−1.6)2.1 (1.4−3.1)***2.2 (1.5−3.3)***1.4 (0.8−2.5)1.3 (0.7−2.4)
      Lake Victoria0.9 (0.6−1.5)1.1 (0.7−1.8)4.2 (2.9−6.1)***4.3 (2.9−6.3)***1.7 (0.9−3.1)1.7 (0.9−2.9)
      FeverYes0.8 (0.4−1.5)-2.5 (1.5−3.9)***2.4 (1.5−4.1)***2.4 (1.1−4.5)*2.1 (0.9−4.1)
      Mosquito bitesYes1.7 (1.3−2.3)***1.4 (1.1−1.9)**1.3 (1.0−1.6)-0.9 (0.6−1.3)-
      Stagnant water around homeYes2.6 (1.8−3.7)***1.8 (1.2−2.6)**1.2 (0.8−1.7)-1.3 (0.6−2.2)-
      Piped waterYes1.7 (1.3−2.2)***1.4 (1.1−1.9)**1.1 (0.9−1.4)-0.9 (0.6−1.4)-
      Mosquito net useYes1.3 (0.9−1.7)-1.6 (1.3−2.1)***1.6 (1.3−2.0)***0.8 (0.5−1.1)-
      Visiting minesYes0.7 (0.2−1.7)-0.8 (0.3−1.6)-2.9 (1.1−6.7)**3.2 (1.2−7.6)*
      OR, odds ratio; CI, confidence interval. ***P < 0.001; **P < 0.01; *P < 0.05; Ref. = reference group (OR = 1).

       Potential risk factors for multiple DENV, CHIKV, and ZIKV infections

      Univariate and multivariable analyses showed that older age (>28 years) (P < 0.001) and having piped water (P < 0.01) were significantly associated with higher odds of DENV and CHIKV seropositivity. Fever was significantly associated with an infection of either DENV or CHIKV or ZIKV (P < 0.001). Individuals sampled from health facilities were significantly associated with higher odds of CHIKV+ZIKV seropositivity (P = 0.03) (Table 4). Residents of Lake Victoria zone were significantly at higher risk of exposure to all three pathogens (DENV+CHIKV+ZIKV) than residents of the other zones (P < 0.05) (Table 5).
      Table 4Risk factors associated with co-infection with dengue + chikungunya or chikungunya + Zika IgG in the univariate and multivariate logistic regression models
      PathogenExposure risk factorCategoryUnivariateMultivariable
      OR (95% CI)OR (95% CI)
      DENV and CHIKVAge (years)<28Ref.Ref.
      28–423.5 (1.9−6.6)***3.5 (1.9−6.5)***
      >423.9 (2.2−7.3)***4.0 (2.3−7.5)***
      Mosquito net useYes2.0 (1.3−3.2)**1.5 (0.9−2.5)
      Mosquito biteYes1.5 (0.9−2.3)1.1 (0.7−1.8)
      Stagnant water around homeYes2.0 (1.1−3.5)*1.7 (0.9−2.9)
      Piped waterYes2.1 (1.4−3.0)***1.8 (1.2−2.7)**
      CHIKV and ZIKVSampling settingHouseholdRef.Ref.
      Facility2.4 (1.1−5.4)**2.7 (1.3−6.3)**
      OccupationEmployedRef.Ref.
      Farming0.4 (0.2−1.5)0.5 (0.2−1.7)
      Trading0.2 (0.0−0.7)**0.2 (0.0−0.8)
      Student0.2 (0.0−1.1)0.2 (0.1−1.6)
      Ecological zoneCentralRef.Ref.
      Western1.2 (0.4−3.6)1.2 (0.4−3.7)
      North-eastern0.4 (0.1−1.6)0.5 (0.1−1.8)
      Southern Highlands0.8 (0.2−2.9)0.8 (0.2−3.0)
      Lake Victoria3.1 (1.1−9.1)*2.8 (1.1−8.5)*
      OR, odds ratio; CI, confidence interval; CHIKV, chikungunya virus; DENV, dengue virus; ZIKV, Zika virus. ***P < 0.001; **P < 0.01; *P < 0.05; Ref. = reference group (OR = 1).
      Table 5Risk factors associated with multiple arbovirus IgG seropositivity in the univariate and multivariable logistic regression models
      PathogenExposure risk factorCategoryUnivariateMultivariable
      OR (95% CI)OR (95% CI)
      DENV, CHIKV, or ZIKVAge (years)<28Ref.Ref.
      28–421.6 (1.2−1.9)***1.5 (1.2−1.9)**
      >421.9 (1.2−2.4)***1.9 (1.5−2.5)***
      Ecological zoneCentralRef.-
      Western0.9 (0.7−1.2)-
      North-eastern0.7 (0.5−0.9)-
      Southern Highlands0.4 (0.3−0.5)-
      Lake Victoria1.2 (0.9−1.6)-
      FeverYes2.3 (1.4−3.8)***2.5 (1.5−4.2)***
      Mosquito biteYes1.4 (1.1−1.7)**1.3 (1.1−1.6)*
      Stagnant water around homeYes1.6 (1.2−2.3)**1.6 (1.1−2.3)**
      Piped waterYes1.2 (0.9−1.5)-
      Mosquito net useYes1.3 (1.1−1.6)**1.2 (0.9−1.5)
      Visiting minesYes0.9 (0.5−1.9)-
      DENV + CHIKV + ZIKVAge (years)<28Ref.Ref.
      28–425.3 (0.9−10)5.4 (0.9−10)
      >4210 (1.9−19)9.9 (1.8−18)**
      Ecological zoneCentralRef.Ref.
      Western2.0 (0.2−4.2)1.9 (0.1−4.1)
      North-eastern3.5 (0.3−7.6)3.4 (0.3−7.3)
      Southern Highlands5.9 (0.9−11)5.5 (0.9−11)
      Lake Victoria10 (1.7−20)*9.9 (1.5−19)*
      FeverYes3.9 (0.6−14)-
      Mosquito biteYes2.1 (0.7−9.0)-
      Stagnant water around homeYes2.9 (0.7−9.3)-
      Mosquito net useYes2.4 (0.8−10)-
      Visiting minesYes0.1 (0.0−0.4)-
      OR, odds ratio; CI, confidence interval; CHIKV, chikungunya virus; DENV, dengue virus; ZIKV, Zika virus. ***P < 0.001; **P < 0.01; *P < 0.05; Ref. = reference group (OR = 1).

      Discussion

      Chikungunya, dengue, and Zika viruses are closely related mosquito-borne viruses with similar transmission cycles, vectors, and disease manifestations. The findings of this study indicate that the three infections are prevalent across Tanzania. Overall, the seroprevalence was higher for CHIKV than DENV or ZIKV, and it varied between districts and ecological zones. CHIKV infection was most prevalent in the Western zone, DENV in the North-eastern zone, and ZIKV in the Central zone. The lowest seropositivity rates of the three arbovirus infections were observed in the semi-arid district of the Central zone. In Tanzania during the past decade, dengue to a large extent, and chikungunya to a lesser extent, have been reported as important causes of morbidity, mainly in the North-eastern zone (
      • Hertz JT
      • Munishi OM
      • Ooi EE
      • Howe S
      • Lim WY
      • Chow A.
      • et al.
      Chikungunya and dengue fever among hospitalized febrile patients in northern Tanzania.
      ;
      • Chipwaza B
      • Mugasa JP
      • Selemani M
      • Amuri M
      • Mosha F
      • Ngatunga SD.
      • et al.
      Dengue and Chikungunya fever among viral diseases in outpatient febrile children in Kilosa District Hospital, Tanzania.
      ;
      • Vairo F
      • Mboera LEG
      • De Nardo P
      • Oriyo NM
      • Meschi S
      • Rumisha SF.
      • et al.
      Clinical, virologic, and epidemiologic characteristics of dengue outbreak, Dar es Salaam, Tanzania, 2014.
      ). The findings of the current study highlight the presence of the three arboviruses among human populations in almost all zones of Tanzania and indicate a wide circulation of the viruses among asymptomatic individuals, hence unlikely to be diagnosed through the routine health service delivery system.
      In Tanzania, several studies have reported the seroprevalence of CHIKV in different parts of the country. In the present study, the highest CHIKV seroprevalence was found in Buhigwe in the Western zone and Lake Victoria zone. Previous studies in Tanzania have reported between 1.0% and 29.3% CHIKV seroprevalence, with lower prevalence in the Central and Southern Highlands regions (
      • Chipwaza B
      • Mugasa JP
      • Selemani M
      • Amuri M
      • Mosha F
      • Ngatunga SD.
      • et al.
      Dengue and Chikungunya fever among viral diseases in outpatient febrile children in Kilosa District Hospital, Tanzania.
      ;
      • Ndosi R
      • Kwigizile E
      • Ibrahim U
      • Dossajee U
      • Rwiza J
      • Kabanyana C.
      • et al.
      Risk factors for concurrent malaria and arbovirus infections in Handeni, Northeastern Tanzania.
      ;
      • Budodo RM
      • Horumpende PG
      • Mkumbaye SI
      • Mmbaga BT
      • Mwakapuja RS
      • Chilongola JO.
      Serological evidence of exposure to Rift Valley, dengue and chikungunya viruses among agropastoral communities in Manyara and Morogoro regions in Tanzania: A community survey.
      ) and relatively higher prevalence in the Northern-eastern and Lake Victoria zones of the country (
      • Kajeguka DC
      • Kaaya RD
      • Mwakalinga S
      • Ndossi R
      • Ndaro A
      • Chilongola JO.
      • et al.
      Prevalence of dengue and chikungunya virus infections in north-eastern Tanzania: a cross sectional study among participants presenting with malaria-like symptoms.
      ;
      • Kinimi E
      • Shayo M
      • Bisimwa P
      • Angwenyi S
      • Kasanga C
      • Weyer J.
      • et al.
      Evidence of chikungunya virus infection among febrile patients seeking healthcare in selected districts of Tanzania.
      ).
      Similarly to CHIKV, some studies have reported the seroprevalence of DENV in different parts of the country (
      • Vairo F
      • Nicastri E
      • Meschi S
      • Schepisi MS
      • Paglia MG
      • Bevilacqua N.
      • et al.
      Seroprevalence of dengue infection: a cross-sectional survey in mainland Tanzania and on Pemba Island, Zanzibar.
      , 2016;
      • Hertz JT
      • Munishi OM
      • Ooi EE
      • Howe S
      • Lim WY
      • Chow A.
      • et al.
      Chikungunya and dengue fever among hospitalized febrile patients in northern Tanzania.
      ;
      • Chipwaza B
      • Sumaye RD
      • Weisser M
      • Gingo W
      • Kim-Wah Y
      • Amrun SN.
      • et al.
      Occurrence of 4 Dengue virus serotypes and chikungunya virus in Kilombero Valley, Tanzania, during the dengue outbreak in 2018.
      ). However, most of the studies were facility-based, focusing on febrile patients (
      • Hertz JT
      • Munishi OM
      • Ooi EE
      • Howe S
      • Lim WY
      • Chow A.
      • et al.
      Chikungunya and dengue fever among hospitalized febrile patients in northern Tanzania.
      ;
      • Kajeguka DC
      • Kaaya RD
      • Mwakalinga S
      • Ndossi R
      • Ndaro A
      • Chilongola JO.
      • et al.
      Prevalence of dengue and chikungunya virus infections in north-eastern Tanzania: a cross sectional study among participants presenting with malaria-like symptoms.
      ;
      • Chipwaza B
      • Sumaye RD
      • Weisser M
      • Gingo W
      • Kim-Wah Y
      • Amrun SN.
      • et al.
      Occurrence of 4 Dengue virus serotypes and chikungunya virus in Kilombero Valley, Tanzania, during the dengue outbreak in 2018.
      ). The current study included both individuals seeking care at health facilities and those found at home. The findings showed that the prevalence of DENV antibodies was higher among those sampled in the household setting than those sampled at health facilities. Previous studies have reported higher prevalence rates of DENV infections among febrile patients in Kilosa, Kinondoni, and Ilala districts, which are located in the Central and North-eastern zones (
      • Vairo F
      • Mboera LEG
      • De Nardo P
      • Oriyo NM
      • Meschi S
      • Rumisha SF.
      • et al.
      Clinical, virologic, and epidemiologic characteristics of dengue outbreak, Dar es Salaam, Tanzania, 2014.
      ;
      • Chipwaza B
      • Sumaye RD
      • Weisser M
      • Gingo W
      • Kim-Wah Y
      • Amrun SN.
      • et al.
      Occurrence of 4 Dengue virus serotypes and chikungunya virus in Kilombero Valley, Tanzania, during the dengue outbreak in 2018.
      ). On the other hand, relatively lower DENV prevalence in Tanzania has been reported among febrile patients in Temeke, Moshi, Iringa, Kilombero, Pemba, and Babati, indicating spatial variations in these infections (
      • Hertz JT
      • Munishi OM
      • Ooi EE
      • Howe S
      • Lim WY
      • Chow A.
      • et al.
      Chikungunya and dengue fever among hospitalized febrile patients in northern Tanzania.
      ;
      • Vairo F
      • Nicastri E
      • Meschi S
      • Schepisi MS
      • Paglia MG
      • Bevilacqua N.
      • et al.
      Seroprevalence of dengue infection: a cross-sectional survey in mainland Tanzania and on Pemba Island, Zanzibar.
      , 2016;
      • Faustine NL
      • Sabuni EJ
      • Ndaro AJ
      • Paul E
      • Chikungunya Chilongola JO.
      Dengue and West Nile virus Infections in Northern Tanzania.
      ;
      • Chipwaza B
      • Sumaye RD
      • Weisser M
      • Gingo W
      • Kim-Wah Y
      • Amrun SN.
      • et al.
      Occurrence of 4 Dengue virus serotypes and chikungunya virus in Kilombero Valley, Tanzania, during the dengue outbreak in 2018.
      ). In this study, ZIKV was most prevalent in Mvomero district, in Central Tanzania. Studies elsewhere in Africa have reported a slightly higher prevalence of ZIKV in Senegal, but a lower prevalence in Cameroon, The Gambia, and Mali (
      • Marchi S
      • Viviani S
      • Montomoli E
      • Tang Y
      • Boccuto A
      • Vicenti I
      • et al.
      Zika Virus in West Africa: A Seroepidemiological Study between 2007 and 2012.
      ;
      • Nguyen CT
      • Moi ML
      • Le TQM
      • Nguyen TTT
      • Vu TBH
      • Nguyen HT
      • Pham TT
      • et al.
      Prevalence of Zika virus neutralizing antibodies in healthy adults in Vietnam during and after the Zika virus epidemic season: a longitudinal population-based survey.
      ).
      Adults accounted for the majority of those with CHIKV infections. The tendency of the arboviruses to affect older populations has been reported in other studies. In a recent study in Vietnam, the prevalence of recent ZIKV infection was highest in the 46–60 years age group (
      • Nguyen CT
      • Moi ML
      • Le TQM
      • Nguyen TTT
      • Vu TBH
      • Nguyen HT
      • Pham TT
      • et al.
      Prevalence of Zika virus neutralizing antibodies in healthy adults in Vietnam during and after the Zika virus epidemic season: a longitudinal population-based survey.
      ). Similarly, higher DENV prevalence rates were observed among older than younger individuals, an observation that corresponds with the findings of studies in Malaysia (
      • Dhanoa A
      • Hassan SS
      • Jahan NK
      • Reidpath DD
      • Fatt QK
      • Ahmad MP.
      • et al.
      Seroprevalence of dengue among healthy adults in a rural community in Southern Malaysia: a pilot study.
      ) and elsewhere in Africa (
      • Mwanyika GO
      • Mboera LEG
      • Rugarabamu S
      • Ngingo B
      • Sindato C
      • Lutwama JJ
      • et al.
      Dengue virus infection and associated risk factors in Africa: A systematic review and meta-analysis.
      ). A low DENV prevalence among individuals <15 years old has also been reported recently in Cameroon (
      • Tchuandom SB
      • Tchadji JC
      • Tchouangueu TF
      • Biloa MZ
      • Atabonkeng EP
      • Fumba MIM.
      • et al.
      A cross-sectional study of acute dengue infection in paediatric clinics in Cameroon.
      ). As in the current study, the association of age with DENV infection in Zambia showed that those aged <5 years expressed a lower risk of DENV seropositivity than those aged ≥45 years (
      • Mazaba-Liwewe ML
      • Sizya S
      • Monze M
      • Mweene-Ndumba I
      • Masaninga F
      • Songolo P.
      • et al.
      First sero-prevalence of dengue fever specific immunoglobulin G antibodies in Western and North-Western provinces of Zambia: a population based cross sectional study.
      ). Like in CHIKV and DENV, higher ZIKV prevalence is frequent among the older individuals. In a study in Vietnam, the prevalence of ZIKV infections was highest in the 46–60 years age group (
      • Nguyen CT
      • Moi ML
      • Le TQM
      • Nguyen TTT
      • Vu TBH
      • Nguyen HT
      • Pham TT
      • et al.
      Prevalence of Zika virus neutralizing antibodies in healthy adults in Vietnam during and after the Zika virus epidemic season: a longitudinal population-based survey.
      ), while in Brazil it was highest among those 20–45 years old (
      • Barreto FK
      • Alencar CH
      • Araújo FM
      • Oliveira RM
      • Cavalcante JW
      • Lemos D.R.
      • et al.
      Seroprevalence, spatial dispersion and factors associated with flavivirus and chikungunya infection in a risk area: a population-based seroprevalence study in Brazil.
      ).
      Logistic regression analysis showed higher odds of CHIKV seropositivity among individuals with fever. Chikungunya normally presents with an abrupt onset of high fever, with the majority of individuals infected developing fever, compared with DENV and ZIKV infections which are sub-clinical in the majority of infected individuals (
      • Martinez JD
      • Cardenas-de la Garza JA
      • Cuellar-Barboza A.
      Going viral 2019: Zika, chikungunya, and dengue.
      ). In this study, about half of those who had fever at the time of recruitment were positive for CHIKV IgG antibodies. The findings of the present study agree with the results from previous studies (
      • Pinzón-Redondo H
      • Paternina-Caicedo A
      • Barrios-Redondo K
      • Zarate-Vergara A
      • Tirado-Pérez I
      • Fortich R
      • et al.
      Risk Factors for Severity of Chikungunya in Children: A Prospective Assessment.
      ;
      • Kinimi E
      • Shayo M
      • Bisimwa P
      • Angwenyi S
      • Kasanga C
      • Weyer J.
      • et al.
      Evidence of chikungunya virus infection among febrile patients seeking healthcare in selected districts of Tanzania.
      ). Moreover, the study results indicate that living in Kinondoni and Mvomero districts, increasing age, experiencing regular mosquito bites, piped water at home, and the presence of stagnant water around the home were potential factors associated with the risk of DENV exposure. In urban areas like Kinondoni with a high population density, solid waste disposal facilities are poor, providing conducive breeding sites for Aedes mosquitoes (Kholedi et al., 2012;
      • Mukhtar F
      • Wazir M
      • Farooq A.
      Outbreak of dengue fever in Lahore: study of risk factors.
      ;
      • Camara N
      • Ngasala B
      • Leyna G
      • Abade A
      • Rumisha SF
      • Oriyo NM
      • et al.
      Socio-demographic determinants of dengue infection during an outbreak in Dar es Salaam City, Tanzania.
      ). Living in Mvomero and Ukerewe districts and visiting mines were potential risk factors for ZIKV infection. The reasons for this could not be determined, although the risk for ZIKV transmission depends on the presence of vector mosquito species as a function of environmental suitability (Gardner et al., 2018).
      Overall, there was a significant difference in multiple exposure to DENV, CHIKV, and ZIKV between districts. The highest DENV+CHIKV seropositivity was recorded among individuals in Kinondoni, and the highest CHIKV+ZIKV seropositivity was found in Ukerewe district. Except for CHIKV+ZIKV multiple infection, none of the individuals aged <15 years in this study had infections with two arboviruses . In this study, the mean age range of the infected population was statistically higher in the patients infected with ZIKV than in those infected with DENV or CHIKV. A relatively higher prevalence of infections of the three arboviruses has been reported in a study performed at the Columbia–Venezuela border (
      • Carrillo-Hernández MY
      • Ruiz-Saenz J
      • Villamizar LJ
      • Gómez-Rangel SY
      • Martínez-Gutierrez M.
      Co-circulation of dengue, chikungunya, and Zika viruses in patients with febrile syndrome at the Colombian-Venezuelan border.
      ) and among pregnant women in Mexico (
      • Eligio-García L
      • MdP Crisóstomo-Vázquez
      • MdL Caballero-García
      • Soria-Guerrero M
      • Méndez–Galván JF
      • López-Cancino SA.
      • et al.
      Co-circulation of Dengue, Zika and Chikungunya in a group of pregnant women from Tuxtla Gutiérrez, Chiapas: Preliminary data. 2019.
      ). These findings demonstrate the simultaneous co-circulation of DENV, CHIKV, and ZIKV in Tanzania, especially in Kinondoni, Mvomero, and Ukerewe districts. The prevalence of co-circulation indicates the endemicity of the three arboviruses in Tanzania and emphasizes the need for molecular diagnosis to rule out serological cross-reaction and avoid false-positives (
      • Langerak T
      • Mumtaz N
      • Tolk VI
      • van Gorp ECM
      • BE Martina
      • Rockx B.
      • et al.
      The possible role of crossreactive. Dengue virus antibodies in Zika virus pathogenesis.
      ).
      Due to high homologies of antigens within the Flavivirus genus, which includes DENV and ZIKV, cross-reactivity cannot be completely ruled out within the flaviviruses (
      • Rathore A.P.S.
      • St. John A.L.
      Cross-reactive immunity among Falviruses.
      ). Although, multiple flavivirus infections are possible, particularly in endemic regions, in this study seropositivity to DENV+ZIKV IgG antibodies was considered as possible cross-reactivity. Given the quality of recombinant virus-specific non-structural protein 1 (NS1), the antigen source used in this study, cross-reactivity was between 1% and 3% in all study districts. Similarly, limited cross-reactivity between DENV and ZIKV has been described recently using the same NS1 ELISA kits (
      • Steinhagen K
      • Probst C
      • Radzimski C
      • Schmidt-Chanasit J
      • Emmerich P
      • van Esbroeck M.
      • et al.
      Serodiagnosis of Zika virus (ZIKV) infections by a novel NS1-based ELISA devoid of cross-reactivity with dengue virus antibodies: a multicohort study of assay performance, 2015 t0 2016.
      ).
      Residents of the Lake Victoria zone were significantly at higher risk of CHIKV+ZIKV co-circulation than those in the other zones. Living in Kinondoni and the presence of piped water at home were significant risk factors for DENV and CHIKV co-circulation. Living in Ukerewe, Mvomero, and Kinondoni districts were potential risk factors for DENV and ZIKV co-circulation, while living in Mvomero was a significant risk factor for CHIKV and ZIKV co-circulation. Living in Ukerewe was a potential risk factor for DENV, CHIKV, and ZIKV co-circulation. In contrast, in a study in Malaysia, no associations between arbovirus co-circulation and occupation, study site, or educational level were observed (
      • Dhanoa A
      • Hassan SS
      • Jahan NK
      • Reidpath DD
      • Fatt QK
      • Ahmad MP.
      • et al.
      Seroprevalence of dengue among healthy adults in a rural community in Southern Malaysia: a pilot study.
      ).
      Chikungunya, dengue, and Zika are thought to have originated in Tanzania (
      • Christie J.
      Remarks on "Kidinga Pepo": A peculiar form of exanthematous disease.
      ;
      • Dick GW
      • Kitchen SF
      • Haddow AJ.
      Zika virus. I. Isolations and serological specificity.
      ;
      • Robinson MC.
      An epidemic of virus disease in Southern Province, Tanganyika Territory, in 1952–53. I. Clinical features.
      ). Even though multiple mosquito-borne viral infections have been reported in Tanzania (
      • Hertz JT
      • Munishi OM
      • Ooi EE
      • Howe S
      • Lim WY
      • Chow A.
      • et al.
      Chikungunya and dengue fever among hospitalized febrile patients in northern Tanzania.
      ;
      • Chipwaza B
      • Mugasa JP
      • Selemani M
      • Amuri M
      • Mosha F
      • Ngatunga SD.
      • et al.
      Dengue and Chikungunya fever among viral diseases in outpatient febrile children in Kilosa District Hospital, Tanzania.
      ;
      • Vairo F
      • Mboera LEG
      • De Nardo P
      • Oriyo NM
      • Meschi S
      • Rumisha SF.
      • et al.
      Clinical, virologic, and epidemiologic characteristics of dengue outbreak, Dar es Salaam, Tanzania, 2014.
      ), they have received little attention as public health threats for several decades. Co-circulation of mosquito-borne viral infections is a public health concern, because most often they cause fevers that are usually not considered by clinicians, especially in areas with inadequate laboratory capacities (
      • Crump JA
      • Morrissey AB
      • Nicholson WL
      • Massung RF
      • Stoddard RA
      • Galloway RL.
      • et al.
      Etiology of severe non-malaria febrile illness in northern Tanzania: a prospective cohort study.
      ;
      • Ayorinde AF
      • Oyeyiga AM
      • Nosegbe NO
      • Folarin OA.
      A survey of malaria and some arboviral infections among suspected febrile patients visiting a health centre in Simawa.
      ). Thus, in many areas, malaria is over-diagnosed, and patients without malaria have had poor clinical outcomes (
      • Crump JA
      • Morrissey AB
      • Nicholson WL
      • Massung RF
      • Stoddard RA
      • Galloway RL.
      • et al.
      Etiology of severe non-malaria febrile illness in northern Tanzania: a prospective cohort study.
      ). Accurate and up-to-date epidemiological data on clinical cases of these mosquito-borne viral infections are limited in many areas of sub-Saharan Africa. This is most likely because of the fact that they are asymptomatic, and when they occur, symptoms are generally mild and non-specific, and therefore may not be detected or reported from healthcare facility settings. The findings of this study provide important information for consideration in terms of the epidemiology and interventions of chikungunya, dengue, and Zika in Tanzania.
      While interpreting the findings of this study, it should be noted that due to the high similarity of the target antigens within the flaviviruses, cross-reactivity cannot be ruled out. In secondary infections, IgG antibodies are expressed earlier than in primary infections; as a consequence, we are likely to have missed cases of those who presented with primary viral infections during the acute phase of infection.
      In conclusion, the findings of this study provide evidence of DENV, CHIKV, and ZIKV co-circulation in diverse ecological zones of Tanzania. The widespread distribution of DENV, CHIKV, and ZIKV seroprevalence in the country emphasizes the need for more effective surveillance to monitor their occurrence and spread. It is important that surveillance and diagnostic systems for the three infections are strengthened nationwide to capture information related to arboviruses. The observed arbovirus co-circulation calls for steps to improve the differential diagnosis of febrile syndromes in order to improve clinical management and outcomes.

      Funding

      This study was funded in part by a PANDORA-ID-NET Consortium Grant (EDCTP Reg/Grant RIA2016E-1609) from the European and Developing Countries Clinical Trials Partnership (EDCTP2) Programme, which is supported under Horizon 2020, the European Union Framework Programme for Research and Innovation.

      Ethical approval

      This study received ethical approval from the Tanzania Medical Research Coordinating Committee of the National Institute for Medical Research (Ref. NIMR/HQ/R.8c/Vol 1/1168). Written informed consent was sought from study participants prior to their involvement. Written consent was sought and obtained from the parents/guardian of each participant under 18 years of age.

      Conflict of interest

      All authors have an interest in emerging infectious diseases. All authors declare no conflict of interest.

      Acknowledgements

      We are grateful to the regional and district authorities in Dar es Salaam, Kigoma, Mbeya, Morogoro, Mwanza, Rukwa, and Tanga for their support and permission to conduct this study in their respective areas of jurisdiction. We thank Alexander Raphael, Martin Anditi, Lucas Lazaro, Ramadhan Amir, Elisamia Swai, and Feliciana Rawille for their support in the data and sample collection in the study districts. Mariam Makange, Anna Rogath, and Mhoja Ndalahwa are thanked for their laboratory technical assistance. Dr Debora Kajeguka and Dr Beatrice Chipwaza are thanked for their comments on the early version of the manuscript.

      References

        • Amoako N
        • Duodu S
        • Dennis FE
        • Bonney JH
        • Asante KP.
        • Ameh J.
        • et al.
        Detection of dengue virus among children with suspected malaria.
        Accra, Ghana. Emerg. Infect. Dis. 2018; 24 (10.3201/eid2408.180341): 1544-1547
        • Ayorinde AF
        • Oyeyiga AM
        • Nosegbe NO
        • Folarin OA.
        A survey of malaria and some arboviral infections among suspected febrile patients visiting a health centre in Simawa.
        Ogun State, Nigeria. J. Infect. Public Health. 2016; 9: 52-59
        • Barreto FK
        • Alencar CH
        • Araújo FM
        • Oliveira RM
        • Cavalcante JW
        • Lemos D.R.
        • et al.
        Seroprevalence, spatial dispersion and factors associated with flavivirus and chikungunya infection in a risk area: a population-based seroprevalence study in Brazil.
        BMC Infect Dis. 2020; 20 (https://doi.org/10.1186/s12879-020-05611-5): 881
        • Braack L
        • Gouveia de Almeida AP
        • Cornel AJ
        • Swanepoel R
        • de Jager C.
        Mosquito-borne arboviruses of African origin: review of key viruses and vectors.
        Parasit Vectors. 2018; 11 (10.1186/s13071-017-2559-9): 29
        • Budodo RM
        • Horumpende PG
        • Mkumbaye SI
        • Mmbaga BT
        • Mwakapuja RS
        • Chilongola JO.
        Serological evidence of exposure to Rift Valley, dengue and chikungunya viruses among agropastoral communities in Manyara and Morogoro regions in Tanzania: A community survey.
        PLoS Negl Trop Dis. 2020; 14 (10.1371/journal.pntd.0008061)e0008061
        • Camara N
        • Ngasala B
        • Leyna G
        • Abade A
        • Rumisha SF
        • Oriyo NM
        • et al.
        Socio-demographic determinants of dengue infection during an outbreak in Dar es Salaam City, Tanzania.
        Tanzania J Health Res. 2018; 20 (http://dx.doi.org/10.4314/thrb.v20i2.3)
        • Carrillo-Hernández MY
        • Ruiz-Saenz J
        • Villamizar LJ
        • Gómez-Rangel SY
        • Martínez-Gutierrez M.
        Co-circulation of dengue, chikungunya, and Zika viruses in patients with febrile syndrome at the Colombian-Venezuelan border.
        BMC Infect Dis. 2018; 18 (https://doi.org/10.1186/s12879-018-2976-1): 61
        • Chipwaza B
        • Mugasa JP
        • Selemani M
        • Amuri M
        • Mosha F
        • Ngatunga SD.
        • et al.
        Dengue and Chikungunya fever among viral diseases in outpatient febrile children in Kilosa District Hospital, Tanzania.
        PLoS Negl Trop Dis. 2014; 8 (10.1371/journal.pntd.0003335): e3335
        • Chipwaza B
        • Sumaye RD
        • Weisser M
        • Gingo W
        • Kim-Wah Y
        • Amrun SN.
        • et al.
        Occurrence of 4 Dengue virus serotypes and chikungunya virus in Kilombero Valley, Tanzania, during the dengue outbreak in 2018.
        Open Forum Infect Dis. 2020; 8 (https://doi.org/10.1093/ofid/ofaa626): ofaa626
        • Christie J.
        Remarks on "Kidinga Pepo": A peculiar form of exanthematous disease.
        Br Med J. 1872; 1 (PMID: 20746649): 577-579
        • Crump JA
        • Morrissey AB
        • Nicholson WL
        • Massung RF
        • Stoddard RA
        • Galloway RL.
        • et al.
        Etiology of severe non-malaria febrile illness in northern Tanzania: a prospective cohort study.
        PLoS Negl Trop Dis. 2013; 7 (https://doi.org/10.1371/journal.pntd.0002324): e2324
        • Dhanoa A
        • Hassan SS
        • Jahan NK
        • Reidpath DD
        • Fatt QK
        • Ahmad MP.
        • et al.
        Seroprevalence of dengue among healthy adults in a rural community in Southern Malaysia: a pilot study.
        Infect Dis Poverty. 2018; 7 (https://doi.org/10.1186/s40249-017-0384-1): 1
        • Dick GW
        • Kitchen SF
        • Haddow AJ.
        Zika virus. I. Isolations and serological specificity.
        Trans Roy Soc Trop Med Hyg. 1952; 46 (https://doi.org/10.1016/0035-9203(52)90042-4): 509-520
        • Elaagip A
        • Alsedig K
        • Altahir O
        • Ageep T
        • Ahmed A
        • Siam H.
        • et al.
        Seroprevalence and associated entomological and socioeconomic risk factors of Dengue fever in Kassala State, eastern Sudan.
        PLoS Negl Trop Dis. 2020; 14 (https://doi.org/10.1371/journal.pntd.0008918)e0008918
        • Eligio-García L
        • MdP Crisóstomo-Vázquez
        • MdL Caballero-García
        • Soria-Guerrero M
        • Méndez–Galván JF
        • López-Cancino SA.
        • et al.
        Co-circulation of Dengue, Zika and Chikungunya in a group of pregnant women from Tuxtla Gutiérrez, Chiapas: Preliminary data. 2019.
        PLoS Negl Trop Dis. 2020; 14 (https://doi.org/10.1371/journal.pntd.0008880)e0008880
        • Faustine NL
        • Sabuni EJ
        • Ndaro AJ
        • Paul E
        • Chikungunya Chilongola JO.
        Dengue and West Nile virus Infections in Northern Tanzania.
        J Adv Med Res. 2017; : 1-7
        • Forshey BM
        • Guevara C
        • Alberto Laguna-Torress V
        • Cespedes M
        • Vargas J.
        • et al.
        Arboviral Etiologies of Acute Febrile Illnesses in Western South America, 2000–2007.
        PLoS Negl Trop Dis. 2010; 4 (https://doi.org/10.1371/journal.pntd.0000787): e787
        • Gaye A
        • Wang E
        • Vasilakis N
        • Guzman H
        • Diallo D
        • Talla C.
        • et al.
        Potential for sylvatic and urban Aedes mosquitoes from Senegal to transmit the new emerging dengue serotypes 1, 3 and 4 in West Africa.
        PLoS Negl Trop Dis. 2019; 13 (https://doi.org/10.1371/journal.pntd.0007043)e0007043
        • Gould EA
        • Higgs S.
        Impact of climate change and other factors on emerging arbovirus diseases. Trans.
        Roy Soc Trop Med Hyg. 2009; 103 (10.1016/j.trstmh.2008.07.025. PMID: 18799177): 109-121
        • Gubler DJ.
        Dengue, urbanization and globalization: the unholy trinity of the 21st century.
        Trop Med Health. 2011; 39 (Suppl10.2149/tmh.2011-S05): 3-11
        • Gudo ES
        • Falk KI
        • Ali S
        • Muianga AF
        • Monteiro V
        • Cliff J.
        A historic report of Zika in Mozambique: implications for assessing current risk.
        PLoS Negl Trop Dis. 2016; 10 (10.1371/journal.pntd.0005052. PMID: 27930650)e0005052
        • Gulland A
        Continued spread of Zika raises many research questions, WHO says.
        BMJ. 2016; 354 (doi: 10.1136/bmj.i4812. PMID: 27596253): i4812
        • Hertz JT
        • Munishi OM
        • Ooi EE
        • Howe S
        • Lim WY
        • Chow A.
        • et al.
        Chikungunya and dengue fever among hospitalized febrile patients in northern Tanzania.
        Am J Trop Med Hyg. 2012; 86 (10.4269/ajtmh.2012.11-0393): 171-177
        • Hill SC
        • Vasconcelos J
        • Neto Z
        • Jandondo D
        • Zé-Zé L
        • Aguiar R.S.
        • et al.
        Emergence of the Asian lineage of Zika virus in Angola: an outbreak investigation.
        Lancet Infect Dis. 2019; 19 (https://doi.org/10.1016/S1473-3099(19)30293-2): 1138-1147
        • Jones KE
        • Patel NG
        • Levy MA
        • Storeygard A
        • Balk D
        • Gittleman JL
        • et al.
        Global trends in emerging infectious diseases.
        Nature. 2008; 451 (doi: 10.1038/nature06536. PMID: 18288193): 990-993
        • Kading R
        • Brault AC
        • Beckham JD.
        Global perspectives on arbovirus outbreaks: a 2020 snapshot.
        Trop Med Infect Dis. 2020; 5 (10.3390/tropicalmed5030142. PMID: 32906771): 142
        • Kajeguka DC
        • Kaaya RD
        • Mwakalinga S
        • Ndossi R
        • Ndaro A
        • Chilongola JO.
        • et al.
        Prevalence of dengue and chikungunya virus infections in north-eastern Tanzania: a cross sectional study among participants presenting with malaria-like symptoms.
        BMC Infect Dis. 2016; 16 (doi 10.1186/s12879-016-1511-5): 183
        • Karimuribo ED
        • Mutagahywa E
        • Sindato C
        • Mboera L
        • Mwabukusi M
        • Kariuki Njenga M
        • et al.
        A Smartphone App (AfyaData) for innovative one health disease surveillance from community to national levels in Africa: Intervention in disease surveillance.
        JMIR Public Health Surveill. 2017; 3 (10.2196/publichealth.7373PMID: 29254916): e94
        • Kariuki Njenga M
        • Nderitu L
        • Ledermann JP
        • Ndirangu A
        • Logue CH
        • Kelly CHL.
        • et al.
        Tracking epidemic Chikungunya virus into the Indian Ocean from East Africa.
        J Gen Virol. 2008; 89 (10.1099/vir.0.2008/005413-0. PMID: 18931072): 2754-2760
        • Kindhauser MK
        • Allen T
        • Frank V
        • Santhana R
        • Dye C.
        Zika: the origin and spread of a mosquito-borne virus.
        Bull World Health Organ. 2016; 94 (C doi: http://dx.doi.org/10.2471/BLT.16.171082): 675-686
        • Kinimi E
        • Shayo M
        • Bisimwa P
        • Angwenyi S
        • Kasanga C
        • Weyer J.
        • et al.
        Evidence of chikungunya virus infection among febrile patients seeking healthcare in selected districts of Tanzania.
        Infect Ecol Epidemiol. 2018; 8 (https://doi.org/10.1080/20008686.2018.1553460)1553460
        • Labeaud D
        • Bashir F
        • King CH.
        Measuring the burden of arboviral diseases: The spectrum of morbidity and mortality from four prevalent infections.
        Popul Health Metr. 2011; 9 (10.1186/1478-7954-9-1PMID: 21219615): 1
        • Lambrechts L
        • Scott TW
        • Gubler DJ.
        Consequences of the expanding global distribution of Aedes albopictus for dengue virus transmission.
        PLoS Negl Trop Dis. 2010; 4 (10.1371/journal.pntd.0000646PMID: 20520794): e646
        • Langerak T
        • Mumtaz N
        • Tolk VI
        • van Gorp ECM
        • BE Martina
        • Rockx B.
        • et al.
        The possible role of crossreactive. Dengue virus antibodies in Zika virus pathogenesis.
        PLoS Path. 2019; 15 (https://doi.org/10.1371/journal.ppat.1007640)e1007640
        • Lourenço J
        • de Lourdes Monteiro M
        • Valdez T
        • Monteiro Rodrigues J
        • Pybus O
        • Rodrigues Faria N
        Epidemiology of the Zika Virus Outbreak in the Cabo Verde Islands, West Africa.
        PLoS Curr. 2018; 1 (10.1371/currents.outbreaks.19433b1e4d007451c691f138e1e67e8c)
        • Marchi S
        • Viviani S
        • Montomoli E
        • Tang Y
        • Boccuto A
        • Vicenti I
        • et al.
        Zika Virus in West Africa: A Seroepidemiological Study between 2007 and 2012.
        Viruses. 2020; 12 (10.3390/v12060641): 641
        • Martinez JD
        • Cardenas-de la Garza JA
        • Cuellar-Barboza A.
        Going viral 2019: Zika, chikungunya, and dengue.
        Dermatol Clin. 2019; 37 (10.1016/j.det.2018.07.008PMID: 30466692): 95-105
        • Mazaba-Liwewe ML
        • Sizya S
        • Monze M
        • Mweene-Ndumba I
        • Masaninga F
        • Songolo P.
        • et al.
        First sero-prevalence of dengue fever specific immunoglobulin G antibodies in Western and North-Western provinces of Zambia: a population based cross sectional study.
        Virol J. 2014; 11 (10.1186/1743-422X-11-135): 135
        • Mugabe VA
        • Ali S
        • Chelene I
        • Monteiro VO
        • Guiliche O
        • Muianga AF.
        • et al.
        Evidence for chikungunya and dengue transmission in Quelimane, Mozambique: Results from an investigation of a potential outbreak of chikungunya virus.
        PLoS ONE. 2018; 13 (https://doi.org/10.1371/journal.pone.0192110)e0192110
        • Mukhtar F
        • Wazir M
        • Farooq A.
        Outbreak of dengue fever in Lahore: study of risk factors.
        J Ayub Med Coll Abbottabad. 2012; 24: 99-101
        • Mwanyika GO
        • Mboera LEG
        • Rugarabamu S
        • Ngingo B
        • Sindato C
        • Lutwama JJ
        • et al.
        Dengue virus infection and associated risk factors in Africa: A systematic review and meta-analysis.
        Viruses. 2021; 13 (https://doi.org/10.3390/v13040536): 536
        • Ndosi R
        • Kwigizile E
        • Ibrahim U
        • Dossajee U
        • Rwiza J
        • Kabanyana C.
        • et al.
        Risk factors for concurrent malaria and arbovirus infections in Handeni, Northeastern Tanzania.
        Int J Trop Dis Health. 2016; 20 (10.9734/Ijtdh/2016/30632): 1-7
        • Nguyen CT
        • Moi ML
        • Le TQM
        • Nguyen TTT
        • Vu TBH
        • Nguyen HT
        • Pham TT
        • et al.
        Prevalence of Zika virus neutralizing antibodies in healthy adults in Vietnam during and after the Zika virus epidemic season: a longitudinal population-based survey.
        BMC Infect Dis. 2020; 20 (https://doi.org/10.1186/s12879-020-05042-2): 332
        • Pinzón-Redondo H
        • Paternina-Caicedo A
        • Barrios-Redondo K
        • Zarate-Vergara A
        • Tirado-Pérez I
        • Fortich R
        • et al.
        Risk Factors for Severity of Chikungunya in Children: A Prospective Assessment.
        Pediatr Infect Dis J. 2016; 35 (https://doi.org/10.1097/INF.0000000000001135): 702-704
        • Rathore A.P.S.
        • St. John A.L.
        Cross-reactive immunity among Falviruses.
        Frontiers in Immunology. 2020; 11 (https://doi.org/10.3389/fimmu.2020.00334): 334
        • Robinson MC.
        An epidemic of virus disease in Southern Province, Tanganyika Territory, in 1952–53. I. Clinical features.
        Trans Roy Soc Trop Med Hyg. 1955; 49 (https://doi.org/10.1016/0035-9203(55)90080-8): 28-32
        • Simo FBN
        • Bigna JJ
        • Kenmoe S
        • Ndangang MS
        • Temfack E
        • Moundipa PF.
        • et al.
        Dengue virus infection in people residing in Africa: a systematic review and meta-analysis of prevalence studies.
        Sci Rep. 2019; 9 (10.1038/s41598-019-50135-x.): 13626
        • Stanaway JD
        • Shepard DS
        • Undurraga EA
        • Halasa YA
        • Coffeng LE
        • Brady OJ.
        • et al.
        The global burden of dengue: an analysis from the Global Burden of Disease study 2013.
        Lancet Infect Dis. 2016; 16 (doi:https://doi.org/10.1016/S1473-3099(16)00026-8): 712-723
        • Steinhagen K
        • Probst C
        • Radzimski C
        • Schmidt-Chanasit J
        • Emmerich P
        • van Esbroeck M.
        • et al.
        Serodiagnosis of Zika virus (ZIKV) infections by a novel NS1-based ELISA devoid of cross-reactivity with dengue virus antibodies: a multicohort study of assay performance, 2015 t0 2016.
        Euro Surveill. 2016; 21 (https://dx.doi.org/10.2807/1560-7917): 30425
        • Tchuandom SB
        • Tchadji JC
        • Tchouangueu TF
        • Biloa MZ
        • Atabonkeng EP
        • Fumba MIM.
        • et al.
        A cross-sectional study of acute dengue infection in paediatric clinics in Cameroon.
        BMC Public Health. 2019; 19 (10.1186/s12889-019-7252-9): 958
        • Vairo F
        • Coussoud-Mavoungou MPA
        • Ntoumi F
        • Castilletti C
        • Kitembo L
        • Haider N.
        • et al.
        Chikungunya outbreak in the Republic of the Congo, 2019 - epidemiological, virological and entomological findings of a south-north multidisciplinary taskforce investigation.
        Viruses. 2020; 12 (10.3390/v12091020): 1020
        • Vairo F
        • Mboera LEG
        • De Nardo P
        • Oriyo NM
        • Meschi S
        • Rumisha SF.
        • et al.
        Clinical, virologic, and epidemiologic characteristics of dengue outbreak, Dar es Salaam, Tanzania, 2014.
        Emerg Infect Dis. 2016; 22 (10.3201/eid2205.151462): 895-899
        • Vairo F
        • Nicastri E
        • Meschi S
        • Schepisi MS
        • Paglia MG
        • Bevilacqua N.
        • et al.
        Seroprevalence of dengue infection: a cross-sectional survey in mainland Tanzania and on Pemba Island, Zanzibar.
        Int J Infect Dis. 2012; 16 (S1201-9712(11)00202-5 [pii]): e44-e46
        • Vazeille M
        • Moutailler S
        • Coudrier D
        • Rousseaux C
        • Khun H
        • Huerre M.
        • et al.
        Two chikungunya isolates from the outbreak of La Reunion (Indian Ocean) exhibit different patterns of infection in the mosquito, Aedes albopictus.
        PLoS ONE. 2007; 2 (10.1371/journal.pone.0001168): e1168
        • Ward T
        • Samuel M
        • Maoz D
        • Runge-Ranzinger S
        • Boyce R
        • Toledo J.
        • et al.
        Dengue data and surveillance in Tanzania: a systematic literature review.
        Trop Med Int Health. 2017; 22 (10.1111/tmi.12903): 960-970
        • Watanaveeradej V
        • Endy TP
        • Samakoses R
        • Kerdpanich A
        • Simasathien S
        • Polprasert N
        • et al.
        Transplacentally transferred maternal-infant antibodies to dengue virus.
        Am J Trop Med Hyg. 2003; 69: 123-128
      1. WHO. Weekly Bulletin on Outbreaks and other Emergencies. Week 27: 1-7 July 2019. https://apps.who.int/iris/bitstream/handle/10665/325777/OEW27-0107072019.pdf

        • Zeng W
        • Halasa-Rappel YA
        • Durand L
        • Coudeville L
        • Shepard DS
        Impact of a nonfatal dengue episode on disability-adjusted life years: a systematic analysis.
        Am J Trop Med Hyg. 2018; 99 (10.4269/ajtmh.18-0309): 1458-1465