The clinical presentation and outcomes of children infected with newly identified respiratory tract viruses.

Numerous emerging respiratory tract viruses have been identified as significant causes of acute upper and lower respiratory tract illness in children. Human metapneumovirus is a paramyxovirus discovered in 2001 in the Netherlands, with a seasonal occurrence and spectrum of clinical illness most similar to the closely related respiratory syncytial virus. Several new members of the corona-virus family have been identified, including the truly novel agent of severe acute respiratory syndrome and others that probably have been circulating undetected. Avian influenza strains have caused numerous outbreaks with high mortality, including children, and are potential causes of pandemic influenza. Several zoonotic paramyxoviruses, including Nipah and Hendra viruses, have emerged as occasional causes of sever outbreaks of respiratory tract illness in children and adults.