There appear to be two genetic and serotypic clusters of hMPV with two subclusters of each cluster (A1, A2, B1, B2). (Guy Boivin, Laval University, Québec, Canada) A new paramyxovirus, the human metapneumovirus (hMPV), has been recently isolated from Dutch children with respiratory symptoms (van den Hoogen et al., 2001) .