A virus, which causes cold-like symptoms in humans, started out in birds, according to an article published in the December issue of the Journal of General Virology.
The bug crossed over to humans about 200 years ago, the study reported.
Scientists hope their findings will help people understand how potentially deadly viruses emerge in humans.
"We have identified sites on some virus proteins that we can monitor to help identify future dominant strains of the virus," the expert added.
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 percent of respiratory illnesses in children.
"HMPV was first discovered in 2001, but studies have shown that the virus has been circulating in humans for at least 50 years," said Professor Dr Ron Fouchier from ErasmusMC in Rotterdam, The Netherlands.
"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," the expert added.
Metapneumoviruses have high evolutionary rates, similar to those of other RNA viruses such as influenza, hepatitis C and SARS. By understanding the evolution and emergence of these viruses the scientists hope to develop ways of monitoring and predicting the emergence of new pathogenic viruses.