What happened in China during the 1918 influenza pandemic?

  • K.F. Cheng
    Affiliations
    Institute of Chinese Medicine, The Chinese University of Hong Kong, 5/F Clinical Science Building, Prince of Wales Hospital, Shatin, Hong Kong
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  • P.C. Leung
    Correspondence
    Corresponding author. Tel.: +852 2632 2726; fax: +852 2686 8463.
    Affiliations
    Institute of Chinese Medicine, The Chinese University of Hong Kong, 5/F Clinical Science Building, Prince of Wales Hospital, Shatin, Hong Kong
    Search for articles by this author
Open ArchivePublished:March 24, 2007DOI:https://doi.org/10.1016/j.ijid.2006.07.009

      Summary

      Influenza has been, and continues to be, a serious threat to human life. The 1918 influenza pandemic infected nearly one quarter of the world's population and resulted in the deaths of 100 million people. Most of the countries in the world were heavily impacted. What happened in China during this period? Compared with other countries, the severity of infection in China was relatively mild. Did traditional Chinese medicine (TCM) play any role, either in the prevention or treatment of the epidemics? This paper explores the situation in China at that particular time.

      Keywords

      Introduction

      Influenza has afflicted humanity since ancient times. The term influenza used by Gagliarde in 1733,
      • Guang H.
      Study of influenza history.
      is derived from the Italian word ‘influence’, its original meaning implying a disaster sent from the heaven. The ancient Italians believed that there was a close relationship between disaster and astronomical phenomena, and numerous beliefs of a similar nature have been found in the Chinese literature.
      Hippocrates recorded the first known influenza epidemic in 412 BC,

      Xu M. Story of virus. Chapter 5. Lesson from the failure of predecessor. Tianxia Zhazhi December 9, 2003.

      and numerous outbreaks were reported during the Middle Ages. The most notable epidemic, that of the ‘Spanish influenza’, occurred in 1918. Although more than 88 years have passed since that time, and memories of the disaster have become blurred, the sudden emergence of SARS and avian flu has reminded people of this painful past once more.
      The earliest well-attested cases of Spanish influenza were reported among army recruits in military camps in the USA in March 1918,
      • Kolata G.
      Flu—the story of the great influenza pandemic of 1918 and the search for the virus that caused it.
      and it was widespread throughout the world within a short period after World War I. Nearly one-third of Americans were infected,
      • Taubenberger J.K.
      • Reid A.H.
      • Fanning T.G.
      The 1918 influenza virus: a killer comes into view.
      and their life expectancy for this time was decreased by 10–12 years because of the epidemic.
      • Kolata G.
      Flu—the story of the great influenza pandemic of 1918 and the search for the virus that caused it.
      • Grove R.D.
      • Hetzel A.M.
      Vital statistics rates in the United States: 1940–1960.
      In 1917, the average age of the American was 51 years, but two years later in 1919, the average age was only 39 years. The influenza epidemic killed at least 675 000 Americans.
      • Zhang H.
      Review on American influenza in 1918 again.
      • Olson D.R.
      • Simonsen L.
      • Edelson P.J.
      • Morse S.S.
      Epidemiological evidence of an early wave of the 1918 influenza pandemic in New York City.
      How did the influenza come about and spread, and could it have been prevented at all? These questions remain unsolved even today, 88 years later. Nobody can predict when such a global disaster will come again; it is believed that it may occur at any time.

      China in the 1918 pandemics

      When Spanish influenza was spreading over the globe, what was happening in China, far away from the USA and Europe?

      Xu M. Story of virus. Chapter 5. Lesson from the failure of predecessor. Tianxia Zhazhi December 9, 2003.

      Certainly India and the Philippines were affected.
      • Taubenberger J.K.
      • Reid A.H.
      • Fanning T.G.
      The 1918 influenza virus: a killer comes into view.
      Some historians believe that 20 000 000 people may have died in India alone.
      • Laver G.
      • Garman E.
      Pandemic influenza: its origin and control.
      Little quantified material on mortality and morbidity is available for early-twentieth century China. Very few records were found in the literature on the real situation in China during the time when Spanish influenza was sweeping across the world.

      Xu M. Story of virus. Chapter 5. Lesson from the failure of predecessor. Tianxia Zhazhi December 9, 2003.

      Most of the records related to the epidemics and hygiene situation in China at that time were made by foreign missionaries and published in the English journal China Medical Journal, which was the first formal Western medicine journal in China edited by foreign experts, as well as in the Returns of Trade and Trade Reports of Chinese Maritime Customs.
      • Cadbury W.W.
      The 1918 pandemic of influenza in Canton.

      Influenza in China. China Med J 1918;32:608.

      • Stanley A.
      Influenza among the Chinese.
      • Barlow C.H.
      Bronchial casts in a case of influenza.

      Returns of trade and trade reports 1918, Parts 1 and 2. Shanghai: Chinese Maritime Customs; 1919.

      Returns of Trade and Trade Reports 1918, Parts 1 and 2. Shanghai: Chinese Maritime Customs; 1920.

      According to the limited records at that time, China was affected and did not escape the effects of the epidemic.

      Report on the pandemic of influenza 1918–1919. Reports on Public Health and Medical Subjects. Vol. 4. London, UK: His Majesty's Stationery Office; 1920.

      Wu JT (1758–1836). Wenbing Tiaobian (Detailed analysis of epidemic warm diseases).

      In the first phase of the 1918 pandemic in Canton (now called Guangzhou) in Guangdong Province adjacent to Hong Kong, Cadbury reported that most of the cases in the June outbreak were young people 11–20 years of age, with a male preponderance. Later in October of the same year most people infected were between 11 and 15 years of age. Mortality was relatively low, in great contrast to the situation in Europe and the USA, where all ages were apparently affected, with most deaths occurring in young adults, particularly 15–34 year-olds.
      • Noble G.R.
      Epidemiological and clinical aspects of influenza.
      • Taubenberger J.K.
      • Reid A.H.
      • Krafft A.E.
      • Bijwaard K.E.
      • Fanning T.G.
      Initial genetic characterization of the 1918 “Spanish” influenza virus.
      In 1927, Jordan wrote in his book that influenza did occur in early 1918 in China, but the outbreaks were minor, and did not spread widely.
      • Jordan E.
      Epidemic influenza.
      Dr A. Stanley who was employed by the Shanghai Health Bureau at that time, described in a private letter written on February 11, 1919 that, “At the end of May influenza started and lasted until June. In October to November the influenza reoccurred with more serious symptoms. Earlier, most of the patients had headache, extreme fatigue, sore throat and fever; these symptoms lasted 4 to 5 days. Erythema was found on the necks and the patients were usually misdiagnosed as scarlet fever. But from September onwards the pattern of the illness was changed suddenly; the number of influenza patients was sharply increased, often with serious symptoms. Some patients were complicated with bronchitis, pneumonia, and even hemolysis. However the death toll still remained low”.
      • Cadbury W.W.
      The 1918 pandemic of influenza in Canton.
      This report published in the China Medical Journal (English) by the foreign medical practitioner
      • Stanley A.
      Influenza among the Chinese.
      was very close in detail to other relevant reports for the same event at that time except with respect to the death rate.
      • Taubenberger J.K.
      • Reid A.H.
      • Fanning T.G.
      The 1918 influenza virus: a killer comes into view.
      • Noble G.R.
      Epidemiological and clinical aspects of influenza.
      • Taubenberger J.K.
      • Reid A.H.
      • Krafft A.E.
      • Bijwaard K.E.
      • Fanning T.G.
      Initial genetic characterization of the 1918 “Spanish” influenza virus.
      It may be true that in other areas where reporting was less clear, they could have suffered badly. Influenza mortality may have been severe in some places in China in 1918–19. During the pandemic, there were also influenza cases reported in rural areas of China, and the morbidity was apparently higher than for the urban cases.

      Influenza in China. China Med J 1918;32:608.

      According to a report, in a small village of about 200 residents near a town, forty persons were killed within a month. In other villages around the town, funerals could be seen to take place nearly every day. In some villages more than half of the residents suffered from influenza and the death rate was as high as 10%, and the supply of coffins became a problem.
      • Death from influenza among the Chinese
      According to a report in the newspaper Tai Gong Boa, entitled “Autumn storm in Southern Yunnan”, which appeared on September 3, 1918, “although Gejiu city remained prosperous without any epidemic so far, a pandemic suddenly broke out in the last two months. Most residents fell sick. Those who were delayed in treatment or did not receive proper treatment became badly hit and thousands of patients died. This epidemic was the worst for many decades”.

      Ta Kung Pao September 3, 1918.

      At the same time the evidence was extremely strong that in many other places in China, including Hong Kong and Shanghai, influenza mortality in 1918–19 was relatively low compared with the USA and Britain (Table 1). An estimate of the crude death rate from influenza in Shanghai in 1918–19 was 1.3 per thousand, which was much lower compared with the average mortality rates among the infected in other parts of the world in 1918 (2.5% or more).
      • Taubenberger J.K.
      • Reid A.H.
      • Fanning T.G.
      The 1918 influenza virus: a killer comes into view.
      • Reid A.H.
      • Taubenberger J.K.
      The origin of the 1918 pandemic influenza virus: a continuing enigma.
      Table 1Number of deaths recorded as due to influenza for each month during 1918–1920 in Hong Kong and Shanghai
      JanFebMarAprMayJunJulAugSepOctNovDecTotal
      Hong Kong
       19180000110853101709567405
       1919211625417513777308892449
       19203911875383261221430443534542
      Shanghai
       1918000001520019207400418
       191900342111000000723483
       19202058601700000122160
      (Sources: Hong Kong 1922: M45; Shanghai Municipal Council Health Department, 1919, 1920, 1921.)
      The local government of Chengde County in Hebei Province issued an announcement to the Rehe Police Office on October 23, 1918; the announcement said: “recently the county was troubled by epidemics which spread widely in a high speed … When a person became infected, the other family members soon became infected too. If no prompt actions were taken, the situation might be out of control.” The local government took a series of measures to control the pandemics, and instructions such as “houses should be sprayed with limewater or lime powder, and rhubarb and Atractylodes rhizome should be burned to disinfect the air” were given. For prevention, “villagers were advised to drink more soup prepared with powdered mung bean and rock sugar, several times a day.” For those who had been infected, “more than 5000 doses of herbal formula were distributed to the families.” According to the statistics available for the period between October 15, 1918 and November 15, 1922 in the areas governed by the Rehe Police Office (Table 2), the total number of male patients reached 3573, of which 3490 recovered and 67 died. The recovery rate was 97.7% and mortality rate was 1.9%. The total number of female patients reached 2630, of which 2534 patients recovered and 84 died. The recovery rate for females was 96.3%, the death rate was 3.2%.
      • Zhang X.
      • Ma L.
      • Jia S.
      Selected history sources of epidemics in Liaoning and Rehe from 1918 to 1932. Liaoning Provincial Chancery.
      Compare this with San Francisco in the USA, where 23 639 people were infected and 2122 died, giving a death rate as high as 8.98%.
      • Zhang H.
      Review on American influenza in 1918 again.
      Table 2Number of infected, recovered and with unknown outcome, and mortality for the period between October 15, 1918 and November 12, 1922 in Rehe County
      GenderInfectedRecoveredUnknown outcomeMortalityMortality rate
      Male3,573349016671.9%
      Female2,630253412843.2%
      Total6,2036024281512.4%
      (Source: Epidemics in Liaoning and Rehe from 1918 to 1932. Liaoning Provincial Chancery.)
      From the limited available records we are confident that the 1918 Spanish influenza did spread in China from the south (Shanghai, Guangzhou) to the north as far as Harbin,
      • Kolata G.
      Flu—the story of the great influenza pandemic of 1918 and the search for the virus that caused it.
      even to remote regions like Gejiu Yunnan Province. To investigate how widespread influenza was in China in 1918–19, 45 treaty ports of China were reviewed as recorded in the Returns of Trade and Trade Reports for 1918 and 1919. Among them, for seven ports – Changsha, Jiujiang, Hangkou, Fuzhou, Nanning, Lungchow and Tengyueh – no mention was made in the reports for either 1918 or 1919 nor was any other disease or health matter referred to. For another 12 ports – Dalian, Tianjin, Yochow, Wuhu, Zhenjiang, Ningbo, Santuao (Fujian), Shantou, Kowloon, Lappa, Pakhoi and Mengtsz – influenza was not referred to, but there was mention of some other disease or health matter. For the remaining 26 ports, influenza was reported in 1918 or 1919. These ports were situated in different parts of China, from the far northeast (Heilongjiang, Jilin and Liaoling) to Guangdong in the south, with influenza reported from every coastal province in between (Hebei, Shangdong, Jiangsu, Zhenjiang, and Fujian), as well as from some provinces further inland (Guangxi, Hubei, Sichuan and Yunnan).

      Returns of trade and trade reports 1918, Parts 1 and 2. Shanghai: Chinese Maritime Customs; 1919.

      Returns of Trade and Trade Reports 1918, Parts 1 and 2. Shanghai: Chinese Maritime Customs; 1920.

      However the severity of the epidemic in China was apparently not as serious as that in Europe, the USA,
      • Taubenberger J.K.
      • Reid A.H.
      • Fanning T.G.
      The 1918 influenza virus: a killer comes into view.
      and India.
      • Laver G.
      • Garman E.
      Pandemic influenza: its origin and control.
      Hong Kong was also affected by the global pandemic in March 1918 (Table 1), but the state of influenza was mild and the duration of disease was short. A Health Officer, Dr Hickling, wrote a private letter on January 29, 1919. In the letter he explained that, “influenza occurred in spring. It was mild and for most of the patients the symptoms lasted only a few days. However towards October, November and December, symptoms became more serious and often lasted 2 to 3 weeks”. In March only one influenza patient died, but in October, 230 persons died of influenza.
      • Cadbury W.W.
      The 1918 pandemic of influenza in Canton.
      Influenza in Hong Kong, during that period, was still mild, compared with the situation in the USA and Europe. The influenza swept across the world in three major waves between 1918 and 1919. The first wave was in the spring of 1918; it attracted very little attention because pneumonic complications were few and deaths were even fewer. Then the second and third killer waves appeared and statisticians noticed that an unusually large proportion of the flu and pneumonia victims were young adults. Dr McKenuy believed that the first wave of influenza did not cause pneumonia, but in the second wave, more than 20% of the influenza cases were complicated with pneumonia. The typical symptoms when influenza was complicated with pneumonia were chills, rapidly rising body temperature, and bloody sputum. A drop in temperature meant an improvement in condition.
      • Barlow C.H.
      Bronchial casts in a case of influenza.
      According to a report written by Stedeford during 1918 and 1919, in Wenzhou, 10 000 people were affected by the epidemic in May 1918. The state of illness became worse in September 1918 and the number of patients sharply increased, although spread remained controlled. Subsequently, in schools 50–60% of students became infected but no death occurred. At the end of October, the influenza pandemic began to subside.
      • Stanley A.
      Influenza among the Chinese.
      The morbidity in Beijing at that time was also as high as 50%.

      Influenza in China. China Med J 1918;32:608.

      On the whole, records for the influenza pandemic of 1918 in China are very sparse. This fact by itself may indicate that the impact of the 1918 pandemic on China was not as serious as in the USA and Europe. Records from Guangdong were plentiful. The records showed that influenza first occurred in schools, post offices and hospitals in June of that year. In October, influenza cases were also found in mental hospitals. Three weeks later, schools for the blind and theological seminaries were struck.
      • Cadbury W.W.
      The 1918 pandemic of influenza in Canton.
      The overall rate of spread of influenza in China appeared slow and the range of spread appeared limited. How much of this observation was due to the milder virulence of the virus, previous exposure to the virus giving a degree of immunity to the disease, or other factors like small population size or slow transportation, thus limiting the chance of cross infection, remains open to speculation.
      As an active port of China, Canton (Guangdong) accommodated many foreigners at that time, such as missionaries, doctors and businessmen. Apparently few foreigners in Canton suffered from influenza; none of them died of it. The influenza symptoms described in June were mild; apart from chills, temperature ranged between 39 and 40 °C. Other symptoms such as fever, headache, back pain, and leg pain were also observed and some cases had vomiting and fatigue. Only a few cases presented with symptoms of pneumonia and bronchitis. If the outbreak in China was just like the situation in Europe and the USA, the death rate in China should have been higher because at that time the economic and healthcare situation in China was very poor. However the situation appeared different. According to a statistical report of a Guangdong hospital no person died of influenza in June and only four persons died in October 1918. The average mortality was 0.1%. Summarizing the data from Shanghai, Hong Kong and Guangdong, the overall mortality in China was still much lower than other countries and regions in the 1918 influenza pandemic.
      • Cadbury W.W.
      The 1918 pandemic of influenza in Canton.
      Outside China, the mortality of influenza was very high. Within only three months from September to November 1918, the influenza pandemic swept over Norway, Sweden, Canada, Spain, the UK, France, Germany, Senegal, Tanzania, Algeria, Zimbabwe, South Africa, India and Indonesia.

      Report on the pandemic of influenza 1918–1919. Reports on Public Health and Medical Subjects. Vol. 4. London, UK: His Majesty's Stationery Office; 1920.

      In the Philippines, the morbidity was 49% and the death rate 2.3%. In the USA more than 675 000 people died of influenza.
      • Taubenberger J.K.
      • Reid A.H.
      • Fanning T.G.
      The 1918 influenza virus: a killer comes into view.
      • Olson D.R.
      • Simonsen L.
      • Edelson P.J.
      • Morse S.S.
      Epidemiological evidence of an early wave of the 1918 influenza pandemic in New York City.
      In India, the number of dead persons was estimated to be more than 100 000.

      Xu M. Story of virus. Chapter 5. Lesson from the failure of predecessor. Tianxia Zhazhi December 9, 2003.

      • Laver G.
      • Garman E.
      Pandemic influenza: its origin and control.
      During those years, modern medicine was undergoing its early phase of development, and a high mortality was expected in cases of viral infections affecting the lungs. How did patients in China manage to survive better? The above records indicate that influenza was widespread in China in 1918 to 1919, but although severe in some parts, it was mild in many places compared with elsewhere in the world. One explanation is that the 1918–19 influenza virus, or a closely related precursor, originated in China, so that many Chinese had had prior exposure and hence some immunity was obtained. However, after tracing all known outbreaks of respiratory disease in China, Jordan
      • Jordan E.
      Epidemic influenza.
      concluded that none of them “could be reasonably regarded as the true forerunner” of the pandemic. We think the likely explanation is that traditional Chinese medicine may have played an important role.

      Traditional Chinese medicine and epidemics

      In ancient China, over thousands of years, innumerable and valuable experiences have been recorded in the course of fighting epidemics. From 171 to 185 AD, there were several great pandemics in China. Thousands of people lost their lives. For this reason, Chinese medical practitioners in ancient China were already concerned with epidemics, which were described as ‘exogenous febrile diseases’ (EFD). Many Chinese medicine practitioners devoted their whole lives to the study of methods of prevention and treatment of pandemics. Since the Han Dynasty (206 BC to AD 220) nearly every medical book has emphasized the importance of the study of epidemics. There must be around 250 texts written on epidemics from ancient China.
      Ancient healers in China recognized two characteristics of epidemics, viz. high infectiousness and uniform presentation. In Huangdi Neijing (Inner Canon of Huangdi), which was written two thousands years ago, the following is recorded: “when epidemics came, almost everyone would be infected and the symptoms were similar, whatever the ages”. Later, Xu Chen described in his book Shuowen Jiezi in 121 AD that, “so called epidemics mean everybody infected”. Some other healers observed that the spread of an epidemic was related to atmospheres and seasons.
      Recorded epidemics in ancient China were certainly plentiful. From Shi Ji (historical records) from 369 BC to the later stage of the Ming Dynasty (1368–1644), a total of 238 epidemics were recorded, among which 95 were officially entered by government authorities. The descriptions for these great pandemics included phrases such as: “the dead persons were innumerable”, “for most family nearly every member was dead”, “even a whole village extinct”, “every family suffered from the pain of lost family members”.

      Cao Z. Cao Zhi Ji Xiao Zhu. Vol. 1. Beijing: People's Literature Publishing House; 1984. p. 177.

      In the 1918 episode no report from China carried similar messages.
      Why was China spared from a more serious impact of the 1918 influenza pandemic? It is well known that China was an undeveloped and closed-door country at that time, and it is not likely that China's general population used Western medicine as the main means of disease treatment. Traditional Chinese medicine would have been the only form of treatment that the general public relied on.
      Each generation of medical specialists had tried their best to explore the reasons for and the prevention and treatment of the epidemics. Efficacious theories, therapeutic methods and herbal formulations were developed. Besides the herbal preparation therapies, Chinese medical practitioners at the end of the Ming Dynasty and early Qing Dynasty (1644–1911), also developed preventive vaccination techniques for the prevention of smallpox.

      Ge Hong (The Eastern Jing Dynasty, 265–420 AD). Zhouhou Beiji Fong (Handbook of prescriptions for emergency). Beijing: The Commercial Press; 1955.

      • Xie S.
      • Zhang D.
      Spread of Chinese variolation art to the Western World and its influence.
      Historical records suggest that ancient Chinese healers had recognized that there were other useful means for the prevention and treatment of epidemic diseases apart from herbal medicines. Although the treatment of epidemics affecting the respiratory tract was not attempted with methods other than herbal medicines, Chinese healers did attempt to give early and preventive treatment during an epidemic attack.
      • Zhang X.
      • Ma L.
      • Jia S.
      Selected history sources of epidemics in Liaoning and Rehe from 1918 to 1932. Liaoning Provincial Chancery.

      Discussion

      Influenza was widespread in China in 1918–19 as previously mentioned, but it was relatively mild and less lethal than elsewhere in the world, despite the generally poor levels of health at that time. Although some researchers in Western countries believe that many people in China had had some previous exposure to the virus and so had obtained some degree of immunity, we think this may be only one of the explanations; the other likely explanation is that traditional Chinese medicine (TCM) may have played an important role. According to the theory of traditional Chinese medicine, influenza is classified as Wen Bing (epidemic febrile disease) or Shanghan (febrile disease). Well-known examples of effective herbal formulations include mahuang xingren shigao decoction created by Zhang Zhong Jing (Han Dynasty), Sangyju Yin and Yin Qiao Sam (Wu Ju Tong, Qing Dynasty),

      Wu JT (1758–1836). Wenbing Tiaobian (Detailed analysis of epidemic warm diseases).

      and Yu Pin Feng San (Zhu Zheng Hen, Yuan Dynasty).

      Zhu Z, Dai S. Danxi Xinfa (Danxi's mastery of medicine (1347)). Shanghai: Shanghai Sciences and Technology Publishing House; 1959.

      As most of the ancient records are considered empirical experiences, large and well-designed randomized controlled trials (RCTs) on long-term major outcome should be performed. In fact many RCTs have been conducted in China to evaluate the effectiveness of traditional Chinese medicine with encouraging results, but the methodological quality needs to be improved.
      • Tang J.L.
      • Zhan S.Y.
      • Ernst E.
      Review of randomised controlled trials of traditional Chinese medicine.
      The use of Chinese medicine in anti-epidemic therapy has stood the test of time, is still trusted and maintains its popularity. Nevertheless in this modern era when all treatment medications need scientific proof of efficacy and explanations as to their mode of action, the herbal formulae need to be re-investigated. If they are effective against early influenza, how do they work? Is it an antiviral mechanism, or an immuno-modulating mechanism to boost resistance? Since literature research on the impact of Spanish influenza does indicate that the Chinese people in China survived much better than people in the USA and Europe, and Chinese people during that period relied invariably on Chinese herbal medicine as the only source of treatment and prevention, we find ourselves encouraged to go further in our attempts to understand more about Chinese medicine and influenza.
      Conflict of interest: No conflict of interest to declare.

      References

        • Guang H.
        Study of influenza history.
        Dongfang Zhazhi. 1919; 16: 17-120
      1. Xu M. Story of virus. Chapter 5. Lesson from the failure of predecessor. Tianxia Zhazhi December 9, 2003.

        • Kolata G.
        Flu—the story of the great influenza pandemic of 1918 and the search for the virus that caused it.
        Farrar, Straus, and Giroux, New York1999
        • Taubenberger J.K.
        • Reid A.H.
        • Fanning T.G.
        The 1918 influenza virus: a killer comes into view.
        Virology. 2000; 274: 241-245
        • Grove R.D.
        • Hetzel A.M.
        Vital statistics rates in the United States: 1940–1960.
        Government Printing Office, Washington DC1968 (p. 309)
        • Zhang H.
        Review on American influenza in 1918 again.
        Shi Ling. 2003; 4: 97-104
        • Olson D.R.
        • Simonsen L.
        • Edelson P.J.
        • Morse S.S.
        Epidemiological evidence of an early wave of the 1918 influenza pandemic in New York City.
        Proc Natl Acad Sci USA. 2005; 102: 11059-11063
        • Laver G.
        • Garman E.
        Pandemic influenza: its origin and control.
        Microbes Infect. 2002; 4: 1309-1316
        • Cadbury W.W.
        The 1918 pandemic of influenza in Canton.
        China Med J. 1920; 34: 1-17
      2. Influenza in China. China Med J 1918;32:608.

        • Stanley A.
        Influenza among the Chinese.
        China Med J. 1919; 33: 391-392
        • Barlow C.H.
        Bronchial casts in a case of influenza.
        China Med J. 1920; 34: 103-104
      3. Returns of trade and trade reports 1918, Parts 1 and 2. Shanghai: Chinese Maritime Customs; 1919.

      4. Returns of Trade and Trade Reports 1918, Parts 1 and 2. Shanghai: Chinese Maritime Customs; 1920.

      5. Report on the pandemic of influenza 1918–1919. Reports on Public Health and Medical Subjects. Vol. 4. London, UK: His Majesty's Stationery Office; 1920.

      6. Wu JT (1758–1836). Wenbing Tiaobian (Detailed analysis of epidemic warm diseases).

        • Noble G.R.
        Epidemiological and clinical aspects of influenza.
        in: Beare A.S. Basic and applied influenza research. CRC Press, Boca Raton, FL, USA1982: 11-50
        • Taubenberger J.K.
        • Reid A.H.
        • Krafft A.E.
        • Bijwaard K.E.
        • Fanning T.G.
        Initial genetic characterization of the 1918 “Spanish” influenza virus.
        Science. 1997; 275: 1793-1796
        • Jordan E.
        Epidemic influenza.
        First ed. AMA, Chicago, IL, USA1927
        • Death from influenza among the Chinese
        China Med J. 1919; 33: 388
      7. Ta Kung Pao September 3, 1918.

        • Reid A.H.
        • Taubenberger J.K.
        The origin of the 1918 pandemic influenza virus: a continuing enigma.
        J Gen Virol. 2003; 84: 2258-2292
        • Zhang X.
        • Ma L.
        • Jia S.
        Selected history sources of epidemics in Liaoning and Rehe from 1918 to 1932. Liaoning Provincial Chancery.
        Republican Archives. 2004; 3: 3-21
      8. Medical ecology. http://medicalecology.org/disease/d_influenza.html (accessed January 2007).

      9. Cao Z. Cao Zhi Ji Xiao Zhu. Vol. 1. Beijing: People's Literature Publishing House; 1984. p. 177.

      10. Ge Hong (The Eastern Jing Dynasty, 265–420 AD). Zhouhou Beiji Fong (Handbook of prescriptions for emergency). Beijing: The Commercial Press; 1955.

        • Xie S.
        • Zhang D.
        Spread of Chinese variolation art to the Western World and its influence.
        Chinese J Med History. 2000; 30: 133-137
      11. Zhu Z, Dai S. Danxi Xinfa (Danxi's mastery of medicine (1347)). Shanghai: Shanghai Sciences and Technology Publishing House; 1959.

        • Tang J.L.
        • Zhan S.Y.
        • Ernst E.
        Review of randomised controlled trials of traditional Chinese medicine.
        BMJ. 1999; 319: 160-161