Table 2. Descriptions of influenza outbreaks^a 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.