The influenssa A ja B , adeno , parainfluenssa type 1 , 2 and 3 as well as respiratory synsytial virus (RSV) antigen and culture, and rhino-, entero- and coronavirus PCR will be performed in the Department of Virology, Turku university, Finland. Human metapneumovirus PCR will be performed in the Department of Virology, Erasmus Medical Center, Rotterdam, The Netherlands. RSV A and B as well as Influenza virus A and B PCR will be performed in the National Health Institute, Helsinki, Finland. Viral and bacteral (C. pneumoniae, M. pneumoniae , S. pneumoniae, H. influenzae ja M. catarrhalis) will be performed in the National Health Institute, Oulu, Finland (17).