The 1957–1958 influenza pandemic, also known as the Asian flu, was a global pandemic of influenza A virus subtype H2N2 that originated in Guizhou, China, and killed at least a million people worldwide.
History
The strain of virus that caused the pandemic, influenza A virus subtype H2N2, was a recombination of avian influenza and human influenza viruses. As it was a novel strain of the virus, the population had minimal immunity. The first cases were reported in Guizhou in late 1956 or early 1957, and they were reported in the neighbouring province of Yunnan before the end of February. On 17 April, The Times reported that "an influenza epidemic has affected thousands of Hong Kong residents". By the end of the month, Singapore also experienced an outbreak of the new flu, which peaked in mid-May with 680 deaths. In Taiwan, 100,000 were affected by mid-May, and 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 Newport Naval Station 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. The microbiologist Maurice Hilleman was alarmed by pictures of those affected by the virus in Hong Kong that were published in The New York Times. He obtained samples of the virus from a US Navy doctor in Japan. The Public Health Service released the virus cultures to vaccine manufacturers on 12 May 1957, and a vaccine entered trials at Fort Ord on 26 July and Lowry Air Force Base on 29 July. The number of deaths peaked the week ending 17 October, with 600 reported in England and Wales. The vaccine was available in the same month in the United Kingdom. Although it was initially available only in limited quantities, its rapid deployment helped contain the pandemic. H2N2 influenza virus continued to transmit until 1968, when it transformed via antigenic shift into influenza A virus subtype H3N2, the cause of the 1968 influenza pandemic.
Mortality estimates
The case fatality rate of Asian flu was approximately 0.67%. The disease was estimated to have a 3% rate of complications and 0.3% mortality in the United Kingdom; it could cause pneumonia by itself without the presence of secondary bacterial infection. It may have infected as many as or more people than the 1918 Spanish flu pandemic, but the vaccine, improved health care, and the invention of antibiotics to manage opportunistic bacterial infections contributed to a lower mortality rate. Estimates of the number of deaths worldwide vary, with the UK government estimating between one and four million and the Centers for Disease Control and Prevention estimating 1.1 million. According to a study in the Journal of Infectious Diseases, the highest excess mortality occurred in Latin America. About 70,000 to 116,000 people died in the United States, and an estimated 33,000 deaths in the United Kingdom were attributed to the 1957–58 flu outbreak. It caused many infections in children, spread in schools, and led to many school closures. However, the virus was rarely fatal in children and was most deadly in pregnant women, the elderly, and those with pre-existing heart and lung disease. According to the researcher Barbara Sands, some of the excess mortality attributed to the Great Leap Forward in Maoist China may have actually been caused by the 1957 flu.
