Coronavirus (COVID-19) Collection
- The SARS-CoV-2 Omicron variant (B.1.1.529) BA.2 pandemic struck in 2022. Children seemed to have a lower rate of infection than adults at the beginning of the COVID-19 pandemic, but the clinical scenario changed, especially after the Omicron variant outbreak . The transmission of SARS-CoV-2 may vary according to different viral variants, settings, and individuals, and understanding the transmission rate and factors associated with transmission may help further control COVID-19. To this end, the difference in clinical symptoms and overall household transmission rate between children and adults needs further investigation.
- From the end of 2020, multiple variants of concern have emerged during the COVID-19 pandemic. Most recently, the Omicron variant has become dominant worldwide over other strains, with the potential for the emergence of other new variants or subvariants in the future. The Omicron variants have demonstrated increasing transmissibility and therefore are more challenging to control (Kraemer et al., 2021; World Health Organization, 2022). In general, increased transmissibility for a variant indicates an increased transmission strength, a higher transmission speed, or both.
- SARS-CoV-2 variants of concern (VOC) appear to spread more easily. Other emerging variants are also gaining attention, either known as a "variants of interest" (VOI) or "variants under investigation" (VUI), which increase transmission, warranting further studies. Since the onset of the COVID-19 pandemic, the SARS-CoV-2 genomes have accumulated genetic diversity, leading to increased transmission with altered viral properties (Kraemer et al. 2021).
- COVID-19, a new contagious respiratory disease, occurred at the end of 2019, in Wuhan, China (Zu et al., 2020), and spread globally rapidly. Although various endeavors have been taken, the disease has not been well controlled except in a few countries. Up to now, COVID-19 has led to over millions of deaths, and become a pandemic and global public health crisis. The pathogen of COVID-19 was quickly confirmed to be SARS-CoV-2 (Schijns et al., 2020).
- SARS-CoV-2, the virus causing Coronavirus disease 2019 (COVID-19), has infected more than 92 million people and lead to the death of more than 1.9 million people worldwide since its outbreak in December 2019 (WHO, 2020). The disease has a wide range of presentations, from asymptomatic infection to fever, cough, shortness of breath and the loss of taste and smell. Symptoms normally appear 2–14 days following exposure to the virus and may develop into mild upper respiratory tract infections or progress to severe pneumonia, which can progress to acute respiratory distress, shock, multiorgan failure and death (Huang et al., 2020; Wang et al., 2020).
- The outbreak of novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-induced disease, COVID-19, spread rapidly from Wuhan, China, in December 2019. This led to China experiencing a major public health emergency with over 83,000 confirmed cases and 4634 deaths as of June 2020 (Rai et al., 2020). Although there are a few newly developed vaccines and treatments, it is conceivable that without some impact on transmission, the virus will continue to circulate, infect, and cause serious disease, in certain segments of the unvaccinated population.
- A combination of physical distancing measures, if implemented early, can be effective in containing COVID-19—tight border controls to limit importation of cases, encouraging physical distancing, moderately stringent measures such as working from home, and a full lockdown in the case of a probable uncontrolled outbreak.
- The patterns of propagation of the severe acute respiratory syndrome (SARS) outbreak of 2003 were not explained by conventional epidemic models that assumed homogeneity of infectiousness. Instead, the existing datasets were best matched by models that used negative binomial distributions, in which a small proportion of cases were highly infectious (Lloyd-Smith et al., 2005; McDonald et al., 2004; Shen et al., 2004). Data and modelling supported the existence of superspreaders, which played a crucial role in propagating the disease by being very efficient at transmitting SARS-CoV-1, such that in the absence of superspreading events most cases infected few, if any, secondary contacts (Stein, 2011).