Mosquitoes in Lewis and Clark County have tested positive for West Nile virus, the City-County health Department announced Wednesday.

As of Wednesday afternoon, there were no confirmed human or animal cases in the county.

There has been one human West Nile case reported in Montana this year, in Richland County. In addition, three horses have been confirmed, two in Lake County and one in Jefferson County.

Lewis and Clark is the fourth county in the state to have confirmed cases of mosquitoes carrying the virus, according to the health department. The others are Cascade, Blaine and Sheridan.

According to Laurel Riek, environmental health specialist with the health department, the majority of people will not be bitten by an infected mosquito, but the virus's presence here should be a reminder to take precautions when outdoors, such as wearing long-sleeved shirts, long pants and hats and using insect repellent.

"The key to prevention is to avoid the mosquito bite," Riek said.

Riek added that usually dusk and dawn are the times of day mosquitoes are most active.

A person bitten by an infected mosquito usually develops symptoms within two to 14 days from the time of the bite. About 20 percent of people who become infected from being bitten get West Nile fever. Symptoms include fever, headache and tiredness. Occasionally, an ill person will have a skin rash on the trunk of the body, eye pain and swollen lymph glands. Symptoms usually last a few days, but some people have reported them up to several weeks.

About 1 percent of people who become infected develop a severe neurological form of infection -- meningitis, which is infection of the lining of the brain or spinal cord, or encephalitis, which is infection of the brain. If a person develops symptoms such as a high fever, confusion, muscle weakness and severe headache, Riek said, it is very important to see a health care provider immediately.

According to the U.S. Centers for Disease Control, 342 people nationwide have been infected with West Nile this year. Of those, 184 have had West Nile fever, while 146 have had encephalitis or meningitis. Three have died.

People who are elderly or whose immune systems are compromised are most often vulnerable to the severe form of illness. The remaining 80 percent of people who are bitten by an infected mosquito will not have any symptoms.

Last year, 202 cases of West Nile were confirmed in Montana, including four deaths and 37 cases of encephalitis or meningitis. Ten people were confirmed with the virus in Lewis and Clark County.

According to Riek, now that the virus has been confirmed in the county, it will be here until winter's arrival.

This story was first reported on helenair.com Wednesday at 12:22 p.m.

On the Web

To learn more about West Nile virus, click here or call the health department at 443-2584.

Health department recommends precautions against West Nile virus

The Lewis and Clark City-County Health Department recommends the following precautions to prevent infection from West Nile virus:

• Keep skin protected. Wear long sleeved shirts and long pants, socks and hats when outdoors from dusk to dawn or during mid-day if in wooded areas or tall grass.

• Use an insect repellent such as DEET or Picaridin to cover exposed skin or clothing.

• Do not apply repellent to skin under clothing.

• Do not use repellent on infants two months or younger. Put them in a carrier or stroller and cover with mosquito netting.

• Never use repellent on cuts, wounds or irritated skin.

• Do not apply repellent to eyes or mouth and use sparingly around ears.

• For children, apply repellent first to your own hands then apply to child's exposed skin. You may not want to put any repellent on child's hands.

• Do not spray aerosol or pump products in enclosed areas or around food.

• Always read and follow label instructions for reapplication.

• After returning indoors, wash treated skin with soap and water, or bathe.

• If you or your child develops a rash or reaction from an insect repellent, stop using the repellent. Wash the repellent off with mild soap and water. Call the Poison Control Center (800) 222-1222 for further guidance. Keep repellent to be able to report label information to doctor or Poison Control Center.