As summer turns to fall, it’s still mosquito season in Wisconsin—which means West Nile virus is still circulating.
The state Department of Health announced Thursday that two Wisconsin residents had died from the virus and another was hospitalized.
Although most cases of West Nile virus are asymptomatic, you should still take steps to avoid it. Here’s what you should know about the virus and how to protect yourself.
More: 2 deaths, 1 hospitalization due to West Nile virus cases in Brown, Outagamie and Fond du Lac counties
What is West Nile virus?
According to the U.S. Centers for Disease Control and Prevention, West Nile virus is the most common cause of mosquito-borne disease in the Americas.
It is a flavivirus, or RNA virus, meaning its genetic material consists of ribonucleic acid, which can infect humans, birds and horses.
Where does the West Nile virus come from?
Most people become infected with the West Nile virus in the summer and fall through the bite of an infected mosquito. Mosquitoes transmit the virus via infected birds.
Transmission of the virus between individuals is rare, except through blood transfusions, organ transplants, or from mother to child during pregnancy, childbirth, or breastfeeding.
Is there West Nile virus in Wisconsin?
Yes. The first reports this year that West Nile virus was circulating in Wisconsin came in early August, when a blood test from a Washington County blood donor came back positive for the virus. A dead bird in Chippewa County also tested positive, the state health department said at the time.
There have been two confirmed human cases of West Nile virus and one probable case in Wisconsin so far this year, according to data from the Department of Health. Ten Wisconsin counties have had the virus detected in humans, mosquitoes or other animals this year. Thursday’s deaths were the first reported this year.
More: The West Nile virus has been detected in mosquitoes in Milwaukee County. Here you can find out everything you need to know.
Last week, health officials in the greater Milwaukee area warned residents to take precautions against mosquito bites because mosquitoes in Milwaukee County had tested positive for the virus.
The first cases of West Nile virus in Wisconsin residents were reported in 2002, according to the health department. Between 2013 and 2022, an average of 16 cases were reported each year. Last year, 25 confirmed and probable cases were reported.
What are the symptoms of West Nile virus?
According to the CDC, most people infected with West Nile virus do not feel sick. About one in five people develop symptoms, including:
- Fever
- Headache
- Pain in limbs
- Joint pain
- Vomit
- Diarrhea
- rash
About one in 150 infected people develops severe illness that affects the central nervous system. Symptoms of the more severe illness include high fever, headache, stiff neck, dizziness, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis, according to the CDC.
Do people recover from West Nile virus?
Most people in whom West Nile virus causes fever and other less severe symptoms recover completely. Fatigue and weakness may last for weeks or months.
For people who develop more serious central nervous system disease, recovery may take several weeks or months, and some effects may be permanent. People over 60 are at higher risk of severe illness if infected, as are people with certain medical conditions such as cancer, diabetes, high blood pressure and kidney disease.
About one in ten people who develop this more serious illness die.
Can the West Nile virus be prevented?
There is no vaccine against West Nile virus, so it is best to avoid mosquito bites if possible.
Use mosquito repellent, cover your skin with long-sleeved shirts and long pants, and limit time outdoors between dusk and dawn – the peak times for mosquito activity in Wisconsin. Make sure window and door screens are tightly closed.
Mosquitoes need water to reproduce, so avoid standing water around your home by cleaning gutters and downspouts, removing leaves from low areas, and draining dishes under flowerpots after rain showers.
Is climate change exacerbating the West Nile virus?
Climate change increases the risk of people being exposed to West Nile virus, according to the U.S. Environmental Protection Agency. Warmer and wetter conditions associated with climate change can affect mosquito reproduction and bite rates.
More: Infectious diseases collide with climate change
Madeline Heim is a staff reporter for Report for America covering environmental issues in Wisconsin. Reach her at 920-996-7266 or [email protected].
