Estimates of the reproduction number for seasonal, pandemic, and zoonotic influenza: a systematic review of the literature

Table 2 Reproduction numbers from the 1957 influenza A/H2N2 pandemic

Location	Wave^a	Study population	Mean GT/SI^b	Reproduction number (R)	Basic or effective	Case definition	Reference	Year published
Netherlands	2nd	Community	3	1.39	Basic	Unconfirmed deaths	[38]	2010
United Kingdom	2nd	Community	2.6	1.70	Basic	Unconfirmed deaths	[10]	2006
United Kingdom	2nd	Community	3	1.5–1.6	Basic	Unconfirmed illness	[39]	2008
United Kingdom	2nd	Community	4	1.7–1.8	Basic	Unconfirmed illness	[39]	2008
United Kingdom	2nd	Community	4.1	1.50	Effective	Unconfirmed illness	[25]	2006
United Kingdom	2nd	Community	NR	1.65	Basic	Serology confirmed infection	[26]	2005
USA	2nd	Community	4	1.70	Basic	Unconfirmed illness	[40]	2004
Median reproduction number for the 1957 pandemic: 1.65; Interquartile range 1.53–1.70

^aThe 1957 influenza A/H2N2 pandemic began in February 1957 in southern China and spread to Singapore and Hong Kong in April [1]. The virus was first isolated in the United States in June 1957 and was associated with a mild first wave of illnesses [1, 41]. The peak of the pandemic occurred during the second wave in the Northern Hemisphere in October 1957 and was followed by a third wave in January 1958.
^bThe generation time (GT) or serial interval (SI) assumed in the reproduction number estimation.
^cConfidence interval.
NR = Not reported.
This table is also available as a .csv file as Additional file 2.