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

Table 3 Reproduction numbers from the 1968 influenza A/H3N2 pandemic

Location	Wave^a	Study population	Mean GT/SI^b	Reproduction number (R)	95% CI^c	Basic or effective	Case definition	Reference	Year published
Hong Kong	1st	Community	2.95	1.89		Basic	Unconfirmed illness	[42]	1986
various	1st	Community	4	1.06–2.06		Basic	Serology; laboratory confirmed illness; unconfirmed illness	[43]	2010
various	1st	Confined settings	4	1.08–1.62		Basic	Serology; laboratory confirmed illness; unconfirmed illness	[43]	2010
United Kingdom	1st	Community	4.1	1.80		Effective	Unconfirmed illness	[25]	2006
United Kingdom	2nd	Community	NR	1.85		Effective	Serology confirmed infection	[26]	2005
various	2nd	Community	4	1.08–2.02		Effective	Serology; laboratory confirmed illness; unconfirmed illness	[43]	2010
various	2nd	Confined settings	4	1.43	1.23–1.63	Effective	Serology; laboratory confirmed illness; unconfirmed illness	[43]	2010
Median reproduction number for the 1968 pandemic: 1.80; Interquartile range 1.56–1.85.

^aThe 1968 influenza A/H3N2 pandemic began in Hong Kong in July 1968. Large single waves of illness were reported in the Northern Hemisphere between September 1968 and April 1969 (with peaks occurring in December 1968–January 1969). Large single waves of illnesses were reported in the Southern Hemisphere between June and September 1969. Some countries in the Northern Hemisphere, such as the United Kingdom, did not have an outbreak of H3N2 until the winter of 1969–70.
^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 3.

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