Bulletin of the World Health Organization

The elusive definition of pandemic influenza

Peter Doshi

Volume 89, Number 7, July 2011, 532-538

Table 2. Descriptions of influenza outbreaksa that have carried the “pandemic” label

Year Virus Nickname Descriptions
1918 H1N1 Spanish flu “devastating pandemic” (US CDC)40
“severe” (US CDC)41
“exceptional” (WHO)42
1957 H2N2 Asian flu “comparatively mild” (WHO)42
“substantial pandemic” (WHO)17
“severe” (US CDC)41
“moderate” (US HHS)43
1968 H3N2 Hong Kong flu “moderate” (US CDC)41
“huge economic and social disruption” (UK DoH)44
“mild” (WHO)45
“substantial pandemic” (WHO)17
“Few people who lived through it even knew it occurred.” (John Barry)46
1977 H1N1 Russian flu “mild” (US CDC)41
“benign pandemic” (WHO)17
2009 H1N1 Swine flu “moderate” (WHO)5,47
“largely reassuring clinical picture” (WHO)48

US CDC, United States Centers for Disease Control and Prevention; UK DoH, United Kingdom Department of Health; US HHS, United States Department of Health and Human Services; WHO, World Health Organization.

a Whether it is called an outbreak, epidemic, or pandemic, influenza has a cyclic propensity to capture the world’s attention and to generate large public health responses. However, with the exception of the 1918 pandemic, which all agree was catastrophically severe, the impact of more recent outbreaks carrying the “pandemic” label is difficult to gauge, as their divergent descriptions suggest.