Twelve cases of West Nile virus, an infectious disease agent that first appeared in the United States in 1999, have been reported in Alabama so far this summer. One death has been recorded.

The Alabama Department of Public Health is currently investigating these cases statewide.

Six of these cases have been reported in Montgomery County, which is also where the death occurred.

State Health Officer Don Williamson said Alabama is ahead of where it was in 2008, when 18 cases were diagnosed. 2009 had no cases, and 2010 reported three.

Along with Montgomery County, three other cases were reported in Mobile County, and one each in Baldwin, Jefferson and Tuscaloosa counties.

Doctors in Montgomery County are historically more aggressive with diagnosing the virus, Williamson said, and that is most likely why the majority of cases have been reported there. Many cases are never diagnosed because they result in such mild symptoms.

Tips to prevent exposure to the virus, according to a local health department representative, include using insect repellant and avoid wearing bright colors and cologne as these attract mosquitoes.

“People have been calling and inquiring about it but as far as I know there have been no reported cases in Dallas County,” the representative said.

According to the Alabama Department of Public Health, 80 percent of those infected with the virus show no symptoms at all. Typically people develop symptoms three to 14 days after being bitten by an infected mosquito.

About one in five people infected with the virus develop symptoms such as a fever, headache, body aches, joint pains, vomiting, diarrhea or rash. The Alabama Department of Public Health reiterated the importance of using insect repellant when participating in any outdoor activity to reduce the chances of contracting the virus.

According to the public health announcement, Mosquitoes that can spread these viruses to humans are commonly found in urban and suburban communities as well as rural, freshwater swamp areas. They breed readily in storm sewers, ditches, waste lagoons and artificial containers around houses.

For more information on the disease, visit adph.org.