Epidemiological profile of influenza a cases in southern Brazil in the post-pandemic period

Abstract

Influenza viruses are highly contagious and circulate in all geographical regions. During the 2009 pandemics caused by influenza A(H1N1), the State of Rio Grande do Sul (RS) was the first to detected A(H1N1) cases. In 2010, a broad vaccination program was applied in RS when 44.9% of the population joined the program. During the 2011, a total of 1,433 samples were sent to the Central Laboratory in Porto Alegre (LACEN-RS) for viral detection by qRT-PCR. Only 107 (7.5%) cases of the A(H1N1) virus were confirmed versus 182 (12.7%) cases of seasonal influenza A. The incidence of both influenza types virus was higher in patients aged 0-10 years old. The median viral load was higher in patients infected with seasonal, in comparison to those infected with A(H1N1) virus contrary of pandemic period. In 2011 most of the patients that were infected by influenza A virus (79%, p<0.001), did not receive vaccine. The presence of fever, cough, dyspnea, myalgia and rhinorrhea were the most frequent symptoms (positivity >60%). Furthermore in 2011 only patients infected by pandemic virus died (12.9%, p=0.001) in contrast with 2009 pandemic period when 6% of patients infected by pandemic virus died. In other hand in the whole population (5.3%) the mortality rate was similar that observed in pandemic period (5.9%). These analyses about epidemiological and molecular data provide important scenery about the characteristics of the host-pathogen interaction after massive exposure during pandemic period. © 2013 Baccin T, et al.