Scientists hone in on how viruses might cross from birds to humans

Scientists determine that a common virus that causes respiratory illness in children was passed from birds to humans about 200 years ago.

Human metapneumovirus (HMPV), a common cause of lower respiratory infection in young children, originated in birds and may have been passed to humans, according to new research published in the current issue of the Journal of General Virology. By the age of five, “virtually all children have been exposed to the virus and re-infections appear to be common," said Ron Fouchier of Erasmus Medical Center in Rotterdam, The Netherlands, in a written statement. HMPV causes cold-like symptoms including runny nose, cough, sore throat and fever in humans. The infection can lead to more serious illnesses such as bronchitis and pneumonia. "HMPV was first discovered in 2001, but studies have shown that the virus has been circulating in humans for at least 50 years," said Fouchier. "HMPV is closely related to Avian metapneumovirus C (AMPV-C), which infects birds. Because of the similarity, scientists have suggested that HMPV emerged from a bird virus that crossed the species barrier to infect humans." Metapneumoviruses have high evolutionary rates like other RNA viruses such as influenza, hepatitis C and SARS. Analyzing genetic information obtained from many different strains of HMPV and AMPV-C circulating in humans and birds, the researchers determined that the AMPV-C virus crossed the species barrier to infect humans as the HMPV about 200 years ago. Understanding how the viruses mutate, evolve and cross to humans from other species will help scientists develop better ways to monitor and predict the emergence of new pathogenic viruses. Citation: deGraaf M, Osterhaus AD, Fouchier RA, Holmes EC. Evolutionary dynamics of human and avian metapneumoviruses J Gen Virol. 2008 Dec;89(Pt 12):2933-42.