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Influenza, an update on the 2010-11 season from ECDC

on Fri, 04/12/2013 - 17:37

The 2010–11 influenza season in Europe was the first after the 2009 pandemic and thus raised the interest of the epidemiologists, due to the possibility to draw some indication of the characteristics of the new seasonal influenza. Data from the ECDC’s Annual Epidemiological Report shown that the 2010–11 influenza season started around the 50th week of 2010 and lasted for a median of 10 weeks, with a geographical progression from west to east (see Table 1). Only one out of 28 countries – Luxembourg – reported very high intensity, compared to the nine of the previous pandemic year.

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There are two types of viruses (A and B) that contributed to the annual epidemics, with the A being the most commonly detected (59.6% of the 14030 respiratory specimens collected as sentinel data). The only exceptions to this distribution were Norway and Sweden, where more than 60% of the detected viruses belonged to the type B. Several influenza viruses subtypes were characterized antigenically (Table 2) and there has been a good match between 95.9% of them and those included in the seasonal trivalent influenza vaccine. The report also provide data on antiviral resistance, revealing that 3.2% of influenza A(H1N1)pdm09 viruses tested were resistant to oseltamivir, while no cases of resistance to zanamivir have been found.

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The median age of laboratory-confirmed cases of infection with A(H1N1)pdm09 virus was 41 years, with a male/female ratio of 1.2. These values rose to 48 years and a ratio of 1.3 for those patients needing intensive care. Amongst the laboratory-confirmed influenza cases, 9.6% had a fatal outcome; 88.2% of these patients had at least one underlying condition. Similarly to what happened during the 2009 pandemic, influenza A(H1N1) pdm09 caused disease mainly among young and middle-aged adults, in some pregnant women, and the majority of people with underlying conditions. Circulation of influenza A(H3N2) virus was very limited and this could explain the lower impact of influenza-related severe disease in adults over the age of 65 years.


Both graphs are taken from the Annual Epidemiological Report 2012.

Annual Epidemiological Report 2012: