Pandemic influenza in Africa, lessons learned from 1968: a systematic review of the literature

BACKGROUND To help understand the potential impact of the 2009 H1N1 pandemic in Africa, we reviewed published data from Africa of the two previous influenza pandemics. METHODS We conducted a systematic search of three biomedical databases for articles in any language on 1957 H2N2 or 1968 H3N2 pandemic influenza virus infection in Africa published from January 1950 through August 2008. RESULTS We identified 1327 potentially relevant articles, and 298 warranted further review. Fourteen studies on 1968 H3N2 influenza met inclusion criteria, while two studies identified describing 1957 H2N2 were excluded for data limitations. Among these 14 studies, community attack rates for symptomatic infection during all 1968 pandemic waves were around 20%. However, the proportion infected in communities ranged from 6% in isolated communities to 100% in enclosed populations. A total of 22-64% of sampled clinic patients and 8-72% of hospitalized patients had evidence of 1968 H3N2 virus infection. After the second pandemic wave, up to 41-75% of persons tested had serological evidence of 1968 H3N2 virus infection. CONCLUSION The 1968 H3N2 influenza pandemic, generally regarded as mild worldwide, appears to have had a substantial impact upon public health in Africa. Without more epidemiologic data the impact of the 2009 H1N1 pandemic in Africa cannot be assumed to have been mild. Assessment of the burden of 2009 H1N1 virus and future influenza pandemics in Africa should attempt to assess disease impact by a variety of methods, including substudies among specific populations.