Respiratory viral coinfection among hospitalized patients with H1N1 2009 during the first pandemic wave in Brazil

influenza a coinfections with other respiratory viruses were investigated in 25.8% (41/159) of the samples from patients hospitalized in 2009 at our university hospital. out of the 41 influenza a cases, nine cases (21.9%) were coinfected with other viruses, with a similar frequency among children and adults (p = 0.47), and seasonal influenza cases were more prevalent than h1n1 2009 influenza virus. adenovirus was the most frequently detected (4/9) among coinfected cases. coinfection was not associated with higher morbidity or mortality (p = 0.75).