A newly discovered human pneumovirus isolated from young children with respiratory tract disease

From 28 young children in the Netherlands, we isolated a paramyxovirus that was identified as a tentative new member of the Metapneumovirus genus base d on virological data, sequence homology and gene constellation. Previously , avian pneumovirus was the sole member of this recently assigned genus, he nce the provisional name for the newly discovered virus: human metapneumovi rus. The clinical symptoms of the children from whom the virus was isolated were similar to those caused by human respiratory syncytial virus infectio n, ranging from upper respiratory tract disease to severe bronchiolitis and pneumonia. Serological studies showed that by the age of five years, virtu ally all children in the Netherlands have been exposed to human metapneumov irus and that the virus has been circulating in humans for at least 50 year s.