The 1957–1958 Asian flu pandemic was a global pandemic of influenza A virus subtype H2N2 that originated in Guizhou in Southern China. The number of excess deaths caused by the pandemic is estimated to be 1–4 million around the world (1957–1958 and probably beyond), making it one of the deadliest pandemics in history. A decade later, a reassorted viral strain H3N2 further caused the Hong Kong flu pandemic (1968–1970).
History
Origin and outbreak in China
The first cases were reported in Guizhou of southern China, in 1956 or in early 1957. Observers within China noted an epidemic beginning in the third week of February in western Guizhou, between its capital Guiyang and the city of Qujing in neighbouring Yunnan province. They were soon reported in Yunnan in late February or early March 1957. By the middle of March, the flu had spread all over China.
The People's Republic of China was not a member of the World Health Organization at the time (not until 1981), and did not inform other countries about the outbreak. The United States CDC, however, contradicting most records, states that the flu was "first reported in Singapore in February 1957".
In late 1957, a second wave of the flu took place in Northern China, especially in rural areas. In the same year, in response to the epidemic, the Chinese government established the Chinese National Influenza Center (CNIC), which soon published a manual on influenza in 1958.
International spread
On 17 April 1957, The Times reported that "an influenza epidemic has affected thousands of Hong Kong residents". The same day The New York Times reported that local press estimated at least 250,000 persons were receiving treatment by that time, out of the colony's total population of about 2.5 million. The recent influx of about 700,000 refugees from mainland China had intensified authorities' fears of epidemics and fires due to crowded conditions, and according to a report received by the US Influenza Information Center on 3 May, the disease was said to be occurring mainly among these refugees.
By the end of the month (or as early as February), Singapore also experienced an outbreak of the new flu, which peaked in mid-May with 680 deaths. The only National Influenza Center reporting data to the World Health Organization for the southeast Asian region in 1957 was located in Singapore, and thus the country was the first to notify the WHO on 4 May about an extensive outbreak of the flu which "appeared to have been introduced from Hong Kong". By the end of May, the outbreak had spread across Mainland Southeast Asia and also involved Indonesia, the Philippines, and Japan. In Taiwan, 100,000 were affected by mid-May.
India suffered a million cases by June. In late June, the pandemic reached the United Kingdom.
By June 1957, it reached the United States, where it initially caused few infections. Some of the first people affected were US Navy personnel at destroyers docked at Naval Station Newport and new military recruits elsewhere. The first wave peaked in October and affected mainly children who recently returned to school after summer break. The second wave, in January and February 1958, was more pronounced among elderly people and so was more fatal.
Eurasia
The Government of India Influenza Centre in Coonoor received word of the potential spread of the pandemic to India on 11 May and therefore decided to watch for the arrival of probable cases at Calcutta and Madras and to isolate the virus from such cases there. On 15 May, it was learned that the steamer S.S. Rajula was experiencing an outbreak of influenza en route from Singapore and had been redirected to Madras instead of its first port of call in Negapatam. Upon the ship's arrival on 16 May, 44 active cases of influenza were discovered on board, and the ship was accordingly placed in quarantine at sea and boarded by medical officers to examine and treat the sick. Two days later, four of the nurses who had boarded the ship became ill themselves, and thus the epidemic in India was considered to have begun.
Bombay reported its first cases on 21 May, and cases appeared in Calcutta that same week. Although the infections in Madras were considered the start of the outbreak in India, it is not clear whether Madras was indeed affected first and the other cities were infected as a result or whether all three cities were in fact affected independently of one another. It is likely they were infected independently but within just a few days of one another. Following the discharge of thousands of passengers from SS Rajula on 21 May and SS State of Madras on 28 May, the States of Madras, Mysore, Kerala, and Andhra apparently became heavily infected.
The epidemic spread throughout all of India within six weeks. Across the country the outbreak assumed a pattern of first sweeping through the most crowded cities and then spreading slowly across villages and other towns. Maximum spread appeared to occur during the week of 2–8 June when numerous cities and towns all across the country became involved in the outbreak. Thereafter, the spread became "one in depth and intensity in the areas already affected."
During the first seven weeks of the epidemic (i.e., up to 6 July), its extent (i.e., the proportion of total cases up to 8 February 1958) varied widely across the country. New Delhi, for example, had already experienced 88% of its total caseload, while Bihar had seen only 3% of its total cases. By 10 August, or twelve weeks into the outbreak, most states had experienced at least 75% of their total caseload. The "main wave" of the pandemic in India had thus swept across the entire country within 12 weeks of the introduction of the virus in mid-May. Influenza continued to occur after 10 August, but the incidence of the disease in affected areas merely represented the "permanent infiltration" of the pandemic virus into the population. By 21 November, the epidemic had nearly concluded in all states except Tripura, where there had been a slight increase in activity.
Between 19 May 1957 and 8 February 1958, India reported 4,451,785 cases of influenza and 1,098 deaths, representing a case fatality rate of 242 deaths per 1 million cases.
During the winter of 1956–1957, Japan experienced an influenza epidemic caused by both type A and type B influenza viruses. It began about the end of November 1956, nearly subsiding by the end of the year in the Tokyo area but persisting until March 1957 in some rural areas. Subsequently, no further influenza activity was expected until the following winter. However, at the beginning of May 1957, influenza suddenly broke out again, appearing first in Tokyo and Kyoto Prefectures before spreading to other parts of the main island; by the end of May, the disease had spread all across the country. It was soon confirmed that this new outbreak was due to the novel influenza virus.
The epidemic peaked in mid-June and then declined in the latter half of the month, remaining in only a few prefectures by the middle to end of July. Although it was considered largely over by August, sporadic outbreaks continued to occur throughout the month, mostly in rural areas. Upon the reopening of schools in early September, the epidemic resurged, with scattered outbreaks appearing in primary and secondary schools in various localities. On 22 November, the epidemic was reported as having once again spread across the entire country, though it was considered "to be of limited importance", remaining as mild as it had been in the spring.
By mid-December, over 1 million cases had been reported in school settings, and the outbreak had apparently passed its peak in most areas. There was another small peak in early 1958, though this could be considered merely a protraction of the second wave. Tens of thousands of cases continued to be reported from schools through January, with several Tokyo-area schools closing some of their classes due to outbreaks at the end of the month. The number of new cases had dropped dramatically, however, with 340 reported in 15 schools during the week ending 1 February, as compared with 60,000 in 370 schools between 22 December and 4 January and 258,000 in 1,818 schools during the week ending 30 November.
Japan was one of a few countries that experienced a widespread second wave of morbidity. It was found that areas less affected during the first wave ended up being more so during the second. On the whole, the disease was not very severe, and mortality during the second wave was comparable to that during the first. Still, mortality rates were notably high among infants and the elderly, and in total there were 7,735 deaths, with a case-fatality rate calculated to be 0.8%.
Pandemic influenza reached Iran, Iraq, and Syria in July 1957. Considering the extensive trade between Turkey and Syria and traffic between Turkey and Iran, it was clear that the virus would soon reach Turkey as well. Therefore, the Ministry of Health and Social Welfare initiated the precautionary measures to deal with the passengers arriving in Turkey by air and sea and the Mecca pilgrims arriving over land, sending two specialists at the end of July to observe the situation in the cities in the southeast and to take throat swabs and washings and serum samples for examination. Influenza infections were thus discovered within the civilian population and police and military units.
Cases were detected in Erzurum and Ankara during the first week of August, and by the following week, cases were being reported from almost every part of the country. Given that schools were on holiday and the agricultural population was in the fields at this time, epidemic influenza was observed only in the larger cities and among factory workers, military units, and other concentrated communities during August and September. Once schools opened in October, however, cases began to appear among the students and the disease spread rapidly. Schools soon had to be closed again because 25–30% of students were absent due to illness. The epidemic peaked that same month and then declined through April 1958.
Between August 1957 and May 1958, 378,330 cases of influenza were reported among the civilian population. If twice that number (i.e., 756,660) is taken as the number of unreported and subclinical cases, and the 31,356 military cases are factored in as well, then approximately 1,166,346 persons can be assumed to have suffered from pandemic influenza in Turkey in 1957–1958. Furthermore, a total of 32 deaths from influenza were reported between September 1957 and January 1958, all occurring in individuals under the age of 5 or over the age of 50.
Pandemic influenza appeared in Croatia in August 1957, increased dramatically in September, and then peaked in October. Although the epidemic had largely subsided by the end of the year, infections continued during the first four months of 1958.
The pandemic broke out in East Germany in October 1957 and peaked that same month. After a month of quiescence, there was a recurrence of the epidemic before it finally ended in December.
Pandemic influenza first appeared in the Netherlands in June 1957. Between June and August, sporadic cases occurred as a result of laboratory infection, a visit to an airfield, and introductions from Indonesia, Turkey, England, and Rome and the Near East. The first focus was a school in Bussum, which had no known link with Asia but where the first cases nonetheless appeared on 14 June. Rotterdam was likely another initial focus, as cases appeared there at the end of June in at least three schools. Subsequently to these outbreaks, influenza appeared in several boarding schools and other institutions in Bussum and Rotterdam and in other towns and villages in the vicinity. Foci continued to appear in August, though no widespread epidemics developed yet during this time.