It’s mosquito season again – prevent West Nile virus

The total number of West Nile human disease cases for last year are shown in this map produced for the Centers for Disease Control. Cases in Montana are located in two eastern counties and Cascade County.   Map courtesy of CDC

State and local public health officials are reminding Montanans to take steps to avoid mosquito bites and prevent infection with West Nile Virus. Summer is a prime time for exposure to mosquitoes capable of transmitting WNV.

However, Montanans can reduce their chances of being bitten by following the advice of public health experts. Public health officials are also reminding the public that while WNV is a concern in Montana, Zika virus is not. In fact, the mosquitoes that carry Zika virus have not been found in Montana or neighboring states.

To minimize risk of WNV, experts recommend reducing mosquito populations by removing mosquito-breeding areas in and around the home. Simple steps such as draining birdbaths, wading pools or any container with still water every few days will minimize breeding sites.

Because it is not possible to eliminate all breeding sites, there are several recommendations people can follow to avoid being bitten. This includes wearing and safely using insect repellent when outdoors and wearing pants and long-sleeved shirts when possible.

“The best way to prevent West Nile virus is to take personal precautions to avoid mosquito bites,” said DPHHS Director Richard Opper. “We encourage everyone to take precautions against West Nile while recreating outside this summer.”

The four D’s of West Nile virus prevention should be followed to reduce the chance of mosquito bites.

Dusk/Dawn: Peak mosquitoes biting hours are dusk to dawn. Limit outdoor activity during those times. If you must be outside, be sure to protect yourself from bites.

Dress: Wear long-sleeved shirts and pants to reduce the amount of exposed skin.

Deet: Cover exposed skin with a repellant containing the chemical Deet, which is most effective against mosquito bites.

Drain: Empty any containers holding standing water because they can be excellent breeding grounds for virus-carrying mosquitoes.

WNV is transmitted to humans by infected mosquitoes through bites. Most, about four out of five people infected will experience no symptoms and develop immunity. About one in five infected people develop a low-grade fever, headache and muscle aches that begin a week or two after becoming infected.  Generally, no treatment is needed.

However, in less than one percent of infected people, serious, life-threatening symptoms develop including headache, rash, high fever, stiff neck, mental confusion and other symptoms. Individuals who develop any of these symptoms should see their health-care provider immediately.

The number of WNV human cases in Montana varies from year to year. Over 200 cases were reported in 2003 and 2007, but generally the average is about 10 reported human infections each year. Cases reported are more likely to be those that are severe and about one-third of Montana cases required hospitalization.

“We can’t predict whether we’ll have a summer with little transmission of WNV or a more severe season,” said Christine Mulgrew, DPHHS WNV program manager. “That is why it is important to protect yourself from mosquito bites and eliminate breeding sites around your home. With over 90 percent of cases occurring in August and September, it is time to start actively preventing mosquito bites.”

For more information go to the DPHHS website at

To keep informed about this and other public health topics, consider subscribing to DPHHS Health in the 406 messages by going to


Health in the 406: Focus on prevention of West Nile Virus

Spread to people by the bite of an infected mosquito, West Nile Virus (WNV) has no specific treatment or vaccine, but you can reduce your risk by eliminating standing water near your property, using insect repellant, and wearing protective clothing.

Four out of five people infected with WNV will have no symptoms and develop immunity, one in five will develop a fever with other symptoms, and less than 1 percent develop a serious, sometimes fatal, neurologic illness.

· While the impact of WNV in Montana varies from year to year, risk is greatest east of the continental divide and in mid– to late summer.



What is your favorite part of the Fair?