In the current study, 10 (50%) patients were treated with oseltamivir, whereby in 5 (25%) patients treatment was started several days after the appearance of influenza symptoms or ICU admission. Antiviral treatment is most beneficial when started within 2 days after onset of symptoms. Nevertheless, oseltamivir treatment initiated later than 2 days after the first influenza symptoms is still considered useful in children with influenza pneumonia or to reduce viral shedding in the hospital [19] ; it also seems to reduce the risk of secondary bacterial super-infections, although the mechanisms are not fully understood [13] . In our study, co-infection with more than one bacterial species was found only in patients that did not receive oseltamivir treatment.