During the 2009 pandemic of influenza A (H1N1), many studies reported estimates of the reproduction number from outbreak data. Since then, seroprevalence studies have been conducted in a number of countries to assess the proportion of the population that was infected in the first wave of the pandemic.
Here, we collate the reproduction number estimates, and use mathematical models to reconcile these with serosurvey data.
Most estimates of the reproduction number from outbreaks are in the range of 1.0–2.0, whereas mean estimates calculated from seroprevalence data range from 1.14 to 1.36. Age-specific analysis of these data suggests that the reproduction number for children was approximately 1.6, whereas the reproduction numbers for adults >25 years of age was less than 1.0.
The difference between age-groups may help to explain high estimates of the reproduction number from outbreaks involving a large proportion of child cases.
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From the aNational Centre for Epidemiology and Population Health, Australian National University, Canberra, Australia; and bEpidemiology Unit, Victorian Infectious Diseases Reference Laboratory, Melbourne, Australia.
Submitted 19 May 2011; accepted 23 August 2011; posted 15 November 2011.
The authors reported no financial interests related to this research.
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Correspondence: Kathryn Glass, National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT, 0200, Australia. E-mail: firstname.lastname@example.org.