PHOENIX (AP) — A new study suggests a strain of the West Nile virus is going to remain in Arizona's most populous county for the foreseeable future.
Arizona researchers say the same mild winters that bring snowbirds to Maricopa County also let mosquitoes and certain virus-reservoir birds survive winter to spread West Nile anew when the weather warms up, Phoenix radio station KJZZ reports.
The study concludes the potentially deadly virus seems to be endemic to the county which includes the Phoenix metro area.
West Nile first entered the U.S. in 1999 and was detected in Maricopa County four years later.
A small percentage of those infected with the virus transmitted to humans by the bite of an infected mosquito could die or suffer severe symptoms such as meningitis, encephalitis or paralysis.