On Monday morning, authorities in Illinois, New York, Michigan and Ohio reported possible West Nile Virus deaths in their states, possibly adding to the current total of 16 confirmed deaths from the virus.

This doesn’t mean that the virus is new to the medical world. Since the early summer of 1999, it has been found in birds and people in 34 states and Washington, D.C. Only now does it appear to be spreading east. A man in Richmond and two horses in North Carolina were diagnosed last week.

The virus is spread to people, horses, birds, and other animals through infected mosquitoes, not by animal-to-animal or human-to-human contact (though no infection has been found, people should always use care when working with horses or handling dead animals). Mosquitoes become infected when they feed on infected birds.

In full, the virus is known as &uot;West Nile encephalitis,&uot; which means that it is an inflammation of the brain. Following transmission by an infected mosquito, the virus multiplies in the person’s bloodstream and crosses over into the brain. The virus interferes with operation of the central nervous system and causes inflammation of brain tissue.

To protect themselves from the virus, people should apply insect repellant sparingly to exposed skin. Because mosquitoes may bite through thin clothing, people should spray their clothing as well. Whenever possible, wear long-sleeved shirts and long pants when outdoors. When outdoors with infants, place mosquito netting over their carriers.

Also, consider staying indoors at dusk and in the early evening. Not only does this make it easier to escape the summertime heat, it keeps people away from mosquitoes during the bugs’ peak biting times. To keep mosquitoes outside, install or repair window and door screens.

To avoid helping mosquitoes breed in the local environment, drain standing water, a popular place for mosquitoes to lay eggs. Regularly empty water from flower pots, pet bowls, clogged rain gutters, swimming pool covers, tires, buckets, and other areas that collect water.

The importance of not overreacting must be stressed. Less than one percent of persons infected with the virus will develop severe illness. Once infected, it is assumed that people will develop a lifelong immunity to the virus.