A dead crow found in Columbia has tested positive for the West Nile virus, the first instance of the virus in Howard County this year, according to the state Department of Health and Mental Hygiene.

The crow is the 43rd bird to test positive for the virus this year in Maryland. All but three of the birds were found in Montgomery and Prince George's counties. Infected mosquitoes have been found in Baltimore and Howard counties. No human cases of West Nile infection have been diagnosed in the state this year.

The virus has been found in 31 states this year, up from nine at this time last year. At least 18 cases of West Nile illness have been reported in Louisiana, Mississippi and Texas this year.