They write about their findings in the 27 February online issue of the Proceedings of the National Academy of Sciences.
The lead author of the study is Dr. Suxiang Tong, who leads the team running the Pathogen Discovery Program in the Division of Viral Diseases at the CDC in Atlanta, Georgia.
Tong told the press this is the first time that a flu virus has been identified in bats, but "in its current form the virus is not a human health issue".
He and his colleagues did not find any evidence of human flu virus genetic material in the bat flu virus, and attempts to propagate it in cell cultures and chicken embryos were unsuccessful, "suggesting distinct requirements compared with known influenza viruses".
For the bat flu virus to become a threat to human health it would have to acquire some genes from human flu viruses. There is a process that occurs naturally, called genetic reassortment, where this can happen. For example, when two or more viruses infect a host cell at the same time, they can swap genetic material.
However, although a preliminary investigation did establish that the bat flu virus genes are compatible with the human flu virus, the process of reassortment is a complex chain of events, and the virus would have to change quite a lot for it to actually acquire those genes.
Co-author Dr. Ruben Donis, chief of the Molecular Virology and Vaccines Branch of the CDC's Influenza Division, said:
"Fortunately, initial laboratory testing suggests the new virus would need to undergo significant changes to become capable of infecting and spreading easily among humans."
But even so, should the opportunity for reassortment present itself, then it could just be a matter of time before a version of the bat flu virus with human flu virus properties emerges.
Donis said for reassortment to occur, the bat flu virus would have to be capable of infecting a different animal, such as a pig, horse or dog, at the same time as a human flu virus.
So far, the bat flu virus has only been found in little yellow-shouldered bats. These fruit bats are not native to the US, but quite common in Central and South America. The bats don't bite people, but it is feasible they could shed the virus onto foods like fruit and vegetables that are then eaten by humans and other animals.
Written by Catharine Paddock PhD