Influenza A H1N1 2009 Antibodies in Residents of New South Wales, Australia, after the First Pandemic Wave in the 2009 Southern Hemisphere WinterReportar como inadecuado




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Background

The first wave of pandemic influenza AH1N12009 pH1N1 reached New South Wales NSW, Australia in May 2009, and led to high rates of influenza-related hospital admission of infants and young to middle-aged adults, but no increase in influenza-related or all-cause mortality.

Methodology-Principal Findings

To assess the population rate of pH1N1 infection in NSW residents, pH1N1-specific haemagglutination inhibition HI antibody prevalence was measured in specimens collected opportunistically before 2007–2008; 474 specimens and after August–September 2009; 1247 specimens the 2009 winter, and before the introduction of the pH1N1 monovalent vaccine. Age- and geographically-weighted population changes in seroprevalence were calculated. HI antibodies against four recent seasonal influenza A viruses were measured to assess cross-reactions. Pre- and post-pandemic pH1N1 seroprevalences were 12.8%, and 28.4%, respectively, with an estimated overall infection rate of 15.6%. pH1N1 antibody prevalence increased significantly - 20.6% overall - in people born since 1944 26.9% in those born between 1975 and 1997 but not in those born in or before 1944. People born before 1925 had a significantly higher pH1N1 seroprevalence than any other age-group, and against any seasonal influenza A virus. Sydney residents had a significantly greater change in prevalence of antibodies against pH1N1 than other NSW residents 19.3% vs 9.6%.

Conclusions-Significance

Based on increases in the pH1N1 antibody prevalence before and after the first pandemic wave, 16% of NSW residents were infected by pH1N1 in 2009; the highest infection rates 27% were among adolescents and young adults. Past exposure to the antigenically similar influenza A-H1N11918 is the likely basis for a very high prevalence 49% of prepandemic cross-reacting pH1N1 antibody and sparing from pH1N1 infection among people over 85 years. Unless pre-season vaccine uptake is high, there are likely to be at least moderate rates including some life-threatening cases of pH1N1 infection among young people during subsequent winters.



Autor: Gwendolyn L. Gilbert , Michelle A. Cretikos, Linda Hueston, George Doukas, Brian O-Toole, Dominic E. Dwyer

Fuente: http://plos.srce.hr/



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