Twelve people in Mobile County have now contracted the West Nile virus since August, the Mobile County Health Department announced Friday.

This is the twelfth lab-confirmed case since the first case was announced Aug. 10, officials said.

No identifying information about those infected will be released due to patient privacy rights outlined under the federal Health Insurance Portability and Accountability Act (HIPAA).

"The public should assume that there are mosquitoes carrying the disease throughout Mobile County," said Dr. Bernard H. Eichold II, Health Officer for Mobile County. "Don't let your guard down."

Humans with West Nile Virus and other mosquito-borne diseases often have symptoms of high fever, severe headache, nausea, stiff neck, confusion, muscle weakness, paralysis, disorientation and seizures that are severe enough to require medical attention. In rare cases, West Nile Virus can cause coma or death, Eichold said.

The risk of encephalitis spread by mosquitoes is highest from August through the first freeze in the fall.

Jerry Folse, the director of MCHD's Vector Services, said his department will increase spraying and conduct door-to-door surveys in the immediate areas. Inspectors will also attempt to trap adult mosquitoes and test them for the presence of the virus.

Officials said people who take part in outdoor activities should try to reduce their exposure to mosquitoes and to keep mosquito repellent on hand at all times while outdoors. Mosquito activity is highest at dusk and dawn.

The virus is spread from bird to mosquito to bird. Mosquitoes can spread viruses by feeding on the blood of infected birds and then biting another host animal or mammal such as a human or a horse.

The disease cannot be spread from people or horses. The likelihood of transmission to horses can be reduced by the West Nile Virus and Eastern Equine Encephalitis. Such vaccines are not available for humans.

To report an issue with mosquitoes, call 251-690-8124 or email VectorServices@mchd.org.