A team of scientists has raised concerns about the H9N2 bird flu virus, which has adapted to human cells, posing a potential threat of a human pandemic.
Although cases of person-to-person transmission have not been reported yet, experiments suggest that the virus has become better suited to infect people.
The researchers say more surveillance of the virus is needed.
The focus has been on the H5N1 avian influenza virus in recent years, but scientists are now worried about the spread of other bird viruses, including H9N2.
Author's summary: H9N2 bird flu strain poses pandemic risk.