A virus that causes cold-like symptoms in humans originated in birds and may have crossed the species barrier around 200 years ago, according to an article published in the December issue of the Journal of General Virology. Scientists hope their findings will help us understand how potentially deadly viruses emerge in humans. "Human metapneumovirus may be the second most common cause of lower respiratory infection in young children. Studies have shown that by the age of five, virtually all children have been exposed to the virus and re-infections appear to be common," said Professor Dr Fouchier. "We have identified sites on some virus proteins that we can monitor to help identify future dominant strains of the virus." Human metapneumovirus is related to the respiratory syncytial virus, measles, mumps and parainfluenza viruses. It infects people of all ages but is most common in children under five. Symptoms include runny nose, cough, sore throat and fever. Infection can also lead to more severe illnesses such as bronchitis and pneumonia, which can result in hospitalisation, especially in infants and immunocompromised patients. HMPV infection is most common during the winter and it is believed to cause up to 10% of respiratory illnesses in children.