West Nile Virus has been detected in Illinois

By Claire Wolters | Fact-checked by Barbara Bekiesz
Published May 9, 2024

Key Takeaways

  • A bird in Illinois recently tested positive for West Nile Virus (WNV), signaling that patients are at risk of contracting the illness earlier than usual in the summer season.

  • WNV symptoms are usually mild and include fever, body aches, and nausea; however, more serious WNV symptoms could indicate a patient is experiencing West Nile meningitis or West Nile encephalitis—both of which require prompt medical attention.

  • WNV cycles between birds and mosquitos and can infect humans if they are bitten by a mosquito; practicing safety measures like keeping screens on windows and wearing insect repellant can help keep you and your patients safe from WNV.

A bird in Illinois’ Douglas County tested positive for West Nile Virus (WNV) in April 2024. The state’s public health officials say the finding is an early warning sign for residents to take public health precautions to reduce their risk.[]

WNV typically cycles between mosquitoes and birds in conjunction with the summer mosquito season. Cases are most commonly reported in August and September, according to the US Department of Health and Human Services (HHS).[]

Humans and other animals can become infected with WNV if they are bitten by an infected mosquito. Rarely, WNS can also spread through mechanisms like blood transfusion, organ transplant, or pregnancy and breastfeeding.

Decoding this summer health risk

WNV is the most common of the mosquito-borne diseases—which also include viruses like malaria and Zika—in the continental US. HHS data indicates that a median of 2,205 WNV cases are reported each year, but only about 20% of people infected will display symptoms.

Sherrill Brown, MD, medical director of infection prevention at AltaMed Health Services in Los Angeles, says that WNV and other mosquito-borne viruses pose health risks every summer. However, due to climate change, she adds that these risks may now linger longer than they have in the past.

“Now that the spring and summer seasons tend to be hotter and last longer, mosquitoes have a longer time to breed, especially after increased amounts of precipitation,” Dr. Brown says. “When this occurs, we will have more mosquitoes around to transmit disease.”

West Nile Virus prevention

To reduce the risks of contracting WNV, you can encourage patients to practice safety measures, such as keeping screens on windows, doors, vents, and chimneys, and by wearing insect repellent. It is a good idea to avoid stagnant water, as it can be a breeding ground for mosquitoes.

Other practices Dr. Brown advises are to “always empty containers of standing water and limit water collecting in containers after rain or watering plants.” If your home garden has a rain barrel, it should be protected with a screen and monitored closely in the event mosquitoes or mosquito larvae appear, she adds.

In Illinois, the Department of Public Health encourages the public to follow the “three Rs” of WNV prevention:

  1. Reducing opportunities for mosquitos to get inside the home or to breed

  2. Repelling mosquitoes by wearing recommended clothing and insect repellent

  3. Reporting any areas with stagnant water to the health department

Detection and symptoms

To detect WNV, it is important to know how to recognize symptoms. Because many symptoms overlap with those of other infections and diseases, conducting a physical exam and asking patients about their living or travel environments and any bug bites are good practices.

The CDC lists the following as some common symptoms of WNV:[]

  • Fever

  • Rash

  • Headache

  • Muscle aches

  • Joint pains

  • Nausea

  • Vomiting

  • Diarrhea

Dr. Brown says these symptoms are more likely to be connected to WNV if the patient reports them “after having contact with environments where mosquitoes were present or suspected,” and if the patient is not experiencing a cough and runny nose.

Most people with WNV will develop these symptoms shortly after contact with the mosquito—between 1 to 14 days—and maintain them for about 3 to 6 days, according to Penn Medicine.[] People with mild symptoms can be treated by means of rest, fluids, and OTC medications, according to the CDC. 

However, some people may experience more serious WNV symptoms that could indicate they are experiencing West Nile meningitis or West Nile encephalitis—two conditions that Penn Medicine says require prompt medical attention.

More serious WNV symptoms include:

  • Confusion

  • Unconsciousness, or going into a coma

  • Muscle weakness

  • Stiffness in the neck

  • Weakness of one arm or leg

Urban areas may be at higher risk

Despite WNV’s connection with animals, people who live in rural areas are not necessarily at a greater risk for transmission than those in urban environments, Dr. Brown says. In fact, in some cases, it’s the other way around. 

“Urban and city areas may be the most concerning for mosquito-borne illnesses due to population density,” Dr. Brown explains. “Urban and city areas have many locations for mosquitoes to lay eggs, such as abandoned swimming pools or containers like tires or cans that allow for collection and stagnation of water.”

Educating patients about this virus and how it is contracted may help them stay alert about their personal protection.

What this means for you

West Nile Virus has been detected in a bird in Illinois—and risks for human transmission may be coming earlier than usual. Encouraging your patients to be mindful of wearing insect repellant, covering windows, and avoiding stagnant water can help reduce their risks.

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