A team of scientists has raised concerns about the H9N2 bird flu virus, which has adapted to human cells, potentially sparking a human pandemic.
Although cases of person-to-person transmission have not been reported, experiments suggest that the virus has become better adapted to infect people.
The researchers say more surveillance of the virus is needed.
The focus has been on the avian influenza virus H5N1, but scientists are now concerned about the spread of other bird viruses, including H9N2.
The H9N2 virus has mostly caused minor disease in birds, but its potential to cause a human pandemic should not be ignored.
Author's summary: H9N2 bird flu strain poses pandemic risk.