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Nothing is more annoying than the buzz of a mosquito in your ear as you try to fall asleep. Now, there is a secondary worry because of the rise of West Nile virus.

For a virus that humanity has known of since 1937, West Nile has certainly generated a lot of concern since it first made its presence known in New York in 1999. It was not the first such mosquito-borne virus in the United States. Malaria and yellow fever certainly preceded it, as did St. Louis encephalitis that in 1975 spread through 29 states and killed 95 people.

As with St. Louis encephalitis, however, most people - even those who live in mosquito-endemic areas - never get the disease. The federal Centers for Disease Control and Prevention estimate that less than 1 percent of people who are infected with West Nile virus will develop severe illness. Among those with severe illness, death rates range from 3 percent to 15 percent. They are highest among older people.

That means that of those who are infected with West Nile virus, between 3 and 15 out of 10,000 will die from the disease. And none of this takes into account the people who may be bitten by mosquitoes who do not carry West Nile virus.

What generates the fear? One is, of course, the concern that an individual might be in that small group of people who contract West Nile virus. However, even when St. Louis encephalitis virus was a routine occurrence in cities such as Houston, fear was not as overblown as it has been since West Nile first came on the scene.

Perhaps it is the exotic name given to the virus. The fact is, however, that viruses are named for where they are first identified. In this case, West Nile virus was first isolated from a febrile adult woman in the West Nile District of Uganda in 1937, according to the CDC. Until 1999, it had been found in Africa, Europe, the Middle East, west and central Asia and Oceania. Yet it is still known by the home place of its first recognized victim - West Nile.

In the United States, the disease began in New York in 1999 and quickly spread across the country. So far, the West Nile virus has been documented in 43 states, including Alabama, Arkansas, California, Colorado, Connecticut, Delaware, the District of Columbia, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin and Wyoming. Perhaps it is the rapidity of its spread that frightens people because it seems to jump from state to state so quickly.

This year, as of Sept. 30, there have been 2,405 cases of the disease reported and 117 deaths. It is not a small toll, but it pales beside the estimated 42,000 people who die in automobile accidents each year and the 958,775 who die of cardiovascular related diseases in the United States each year.

It may be true that the virus can be transmitted through donated organs or blood - although the mechanism of that has yet to be determined. The disease is definitely established in the United States and the extent of risk it poses to the blood supply will have to be determined.

The risk of acquiring the disease is highest in those areas where there are mosquitoes and people with the disease have been identified. Those over the age of 50 have the highest risk of acquiring severe disease, as do those whose immune systems are depleted by disease or treatment with certain cancer-fighting drugs.

You can protect yourself. Personal protection using an insect repellent that contains DEET according to manufacturer's instructions can go a long way as will wearing long-sleeved shirts and long pants outdoors - although few people are going to want to do this in the heat of summer and early fall. Infants can be protected by mosquito netting over their carriers when they are out of doors.

Avoid the outdoors at dawn, dusk and in the early evening, when mosquitoes are likely to be outside and biting. Repair or install window and door screens to keep the insects out of your home.

Drain water puddles and pools outside your home. Check containers for standing water, where mosquitoes like to lay their eggs and breed. Clean out clogged rain gutters and removed items that can collect water. These mosquitoes like to breed in stagnant water.

Mosquitoes carry the disease, and minimizing contact with them by reducing their numbers and your hours outdoors can go a long way to decreasing your risk.

Know, however, that the risk will never be zero. Life is a risky business, and no one knows what will strike next where. So roll up a newspaper and swat that mosquito, and then go to sleep, knowing you have done as much as you can.

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