SPRING HILL — One of Hernando County's sentinel chickens has tested positive for West Nile virus, months earlier than normal.

Usually, the West Nile season starts in July. But officials say the unseasonably warm winter has spurred early activity by mosquitoes. West Nile is spread by the bite of infected mosquitoes.

The chicken found with the virus was at the county's wastewater treatment plant at U.S. 19 and Osowaw Boulevard. The positive test indicates that there are mosquitoes infected with West Nile in the area.

Last year, two sentinel chickens in the Royal Highlands area were found infected in August and October. And one chicken at the Osowaw site was found with eastern equine encephalitis in June.

Since the start of the year, the county's mosquito control staff has treated hundreds of sites where mosquitoes have been breeding, including catch basins, condemned swimming pools, drainage ponds and ditches.

No human cases of West Nile have ever been found in the county, and officials, hoping to keep it that way, encourage those who are outdoors at dusk and dawn to wear mosquito repellent.

In humans, West Nile can cause inflammation of the brain. Symptoms of the virus appear four to 10 days after a bite and include sudden onset of headache, high fever, chills and vomiting.

The Florida Department of Health encourages anyone who has been bitten by mosquitoes and is experiencing those symptoms to contact their physician immediately.