In what may be the first known transmission of bird flu from cats to humans, a veterinarian in the US has been infected with a strain of avian flu that spread among more than 100 cats at animal shelters. However, the New York City Department of Health and Mental Hygiene in the US said that its ongoing investigation of the outbreak of H7N2, a strain of influenza A virus, among cats housed at Animal Care Centres shelters confirms that the risk to humans is low.