A second human case of West Nile virus was reported in Marion County, and mosquito groups in 25 counties -- including Lake, Jasper and St. Joseph -- recently tested positive for the virus, state health officials said last week.

"The recent increase in positive West Nile virus mosquitoes suggests there is an increased risk for human cases," said Dr. Jennifer House, veterinarian and director of zoonotic and environmental epidemiology at the Indiana State Department of Health.

People can prevent infection by applying insect repellent containing DEET, picaridin or oil of lemon eucalyptus to clothes and exposed skin, House said. People also should avoid the outdoors during dusk and dawn when mosquitoes are most likely to bite, she said.

West Nile virus usually causes a milder illness called West Nile fever. Those infected experience fever, headache, body aches, swollen lymph glands or rashes. Though rare, people also can develop a more severe form of the disease that causes meningitis and muscle paralysis.

Hoosiers can keep mosquitoes from their homes by discarding unused containers such as old tires and ceramic pots that can hold water, repairing failed septic systems, drilling holes in the bottom of recycling containers left outdoors, keeping grass short and shrubbery trimmed, cleaning clogged roof gutters and flushing birdbaths and fountains.