Pandemic A(H1N1) 2009 influenza: review of the Southern Hemisphere experience.

We sought to systematically review the published literature describing the epidemiological aspects of the first wave of pandemic A(H1N1) 2009 influenza in the Southern Hemisphere. Fifteen studies were included in this review, originating from South America, Australia or New Zealand, and Africa. Across the different studies, 16·8-45·3% of the laboratory-confirmed cases were admitted to hospital, and 7·5-26·0% of these cases were admitted to intensive care units (ICUs). The fatality rate was 0·5-1·5% for laboratory-confirmed cases in 6/8 studies reporting specific relevant data, and 14·3-22·2% for cases admitted to ICUs in 5/7 studies, respectively. In 4/5 studies the majority of laboratory-confirmed cases were observed in young and middle-aged adults, the percentage of older adults increased the higher the level of healthcare the cases received (e.g. laboratory confirmation, hospitalization or ICU admission) or for fatal cases. Many of the cases had no prior comorbidity, including conditions identified as risk factors for seasonal influenza. Pregnant women represented 7·4-9·1% and 7·1-9·1% of unselected laboratory-confirmed cases and of those admitted to ICUs, respectively. Obesity and morbid obesity were more commonly reported as the level of healthcare increased.

Epidemiological aspects of 2009 H1N1 influenza: the accumulating experience from the Northern Hemisphere.

Preliminary data regarding the experience of countries of the Northern Hemisphere with pandemic 2009 A(H1N1) influenza have already appeared in the literature. We aimed to evaluate the available published literature describing the epidemiological features of pandemic influenza. We searched PubMed; 35 studies (14 referred to European countries, eight to the USA, five to Mexico, four to Canada, two to Japan, one to Colombia, and one reviewed relevant data reported worldwide) were included. Considerably high hospitalization, intensive care unit (ICU) admission, and fatality rates (up to 93.8, 36.4, and 38.5%, respectively) among the evaluated cases were reported across studies with available relevant data. Young and middle-aged adults constituted the majority of the evaluated pandemic cases, with different disease severity (as indicated by the level of care and outcome). Yet, substantial percentages of elderly individuals were reported among more severely afflicted cases. Otherwise healthy patients constituted substantial percentages among evaluated cases with different disease severity. Pregnant women, obese, and morbidly obese patients also constituted substantial percentages of the cases involved in the included studies. The evaluation of the currently available published evidence contributes to the clarification of the epidemiological features of pandemic 2009 A(H1N1) influenza, which is useful in terms of the individual and public health perspectives.