Asian Flu
Also known as: 1957 Pandemic
Overview
The Asian flu pandemic of 1957–1958 was caused by an H2N2 influenza A virus that first emerged in Guizhou province, China, in February 1957. The virus was a reassortant combining avian and human influenza genes, to which humans had no immunity.
The pandemic spread rapidly along modern trade and travel routes, reaching Singapore by April, Hong Kong in May, and the United States and Europe by June. A vaccine was developed unusually quickly — by August 1957, less than six months after virus identification — thanks to work by Maurice Hilleman and colleagues at the Walter Reed Army Institute. The rapid vaccine response likely limited the scale of the pandemic in North America and Europe.
Mortality skewed toward the elderly and the very young, unlike the 1918 flu. Worldwide deaths are estimated at 1 to 4 million, with about 70,000–116,000 in the United States. The H2N2 strain replaced the H1N1 strain that had circulated since 1918 and persisted until 1968, when it was in turn replaced by H3N2 (the Hong Kong flu).
Timeline
- February 1957Outbreak in Guizhou, China.
- April 1957Spreads to Singapore, then Hong Kong.
- May 1957Virus isolated; Hilleman identifies novel H2N2 strain.
- June 1957First US cases; US military barracks outbreaks.
- August 1957Vaccine production begins; 40 million doses shipped in US by year's end.
- October 1957Peak mortality in Northern Hemisphere.
- 1968Hong Kong flu pandemic; H2N2 replaced by H3N2.
Impact
The 1957 pandemic is notable for demonstrating that rapid vaccine development could materially reduce mortality. Maurice Hilleman's early virus sampling and the industry's willingness to commit production capacity saved perhaps 1 million lives, particularly in the United States. The pandemic also established the WHO's Global Influenza Surveillance Network as the primary system for detecting novel strains. Excess mortality was far lower than in 1918, partly because of antibiotics for secondary bacterial infections that had killed many 1918 victims.
How it ended
The pandemic faded as population immunity built up. H2N2 continued to circulate as seasonal flu until 1968, when it was replaced by the H3N2 strain of the Hong Kong flu.
Sources
- CDC 1957–1958 Pandemic (H2N2)
- Hilleman, Maurice R. (2002). 'Realities and enigmas of human viral influenza.' Vaccine.
- WHO pandemic preparedness documentation.