The Illinois Department of Public Health (IDPH) reported that a batch of mosquitoes collected in River Forest on May 31 tested positive for West Nile Virus. The mosquitoes were collected by the Des Plaines Valley Mosquito Abatement District (DVMAD), which monitors and works to control the mosquito population in the area. No human cases have been reported yet this year.

Dr. Ngozi Ezike, IDPH health director, said in a statement, “While we continue to battle the COVID-19 pandemic, we must also remember to take steps to protect our health from other illnesses. Getting outdoors is a great way to combat being cooped up, but you need to take precautions to protect yourself from mosquitoes and the viruses they carry by wearing insect repellent and getting rid of standing water around your home.”

Should residents be worried?

Mark Tomek, biologist at the DVMAD, said in an email that at this point, “as we so far only have the single ‘low’ positive, the concern for human transmission is still very low.” Spraying by the DVMAD to control mosquitoes, he said, “is only conducted at times when observed rates of [West Nile Virus] in the mosquito population are high enough that spillover into the human population becomes likely.”

In 2019, said Tomek, no spraying for mosquitoes was done by the DVMAD.

What is West Nile Virus?

West Nile Virus is transmitted through the bite of a Culex pipiens mosquito, also known as a house mosquito, that has picked up the virus by feeding on an infected bird. According to the IDPH, a large majority, four out of five people, infected with West Nile Virus will not show any symptoms. Those who do may experience fever, nausea, headaches and muscle aches, and these symptoms can last from a few days to a few weeks.

In people over 60 and those with weakened immune systems, however, the risk for severe illness from West Nile Virus is higher. Rarely, severe complications can include meningitis, encephalitis or even death.

How is West Nile Virus monitored locally?

Oak Park, River Forest and Proviso Township, which includes Forest Park, are part of DVMAD, which is administered by a board of trustees and employs a small permanent staff and up to 24 seasonal workers. Operations are funded through real estate taxes from the participating townships, according to the abatement district’s website.

The district encompasses a 77 square mile area of the Des Plaines River and Salt Creek valley in the western suburbs, and includes Lyons, Oak Park, Proviso, Riverside, and River Forest, for a total of 31 villages.

The DVMAD monitors for West Nile Virus through laboratory tests of mosquito batches, dead birds (crows, blue jays, robins and other perching birds), and testing symptomatic horses and humans.

What can residents do?

Tomek said there is the potential right now for a rise in the population of mosquitoes that carry West Nile Virus.

“We are going into a stretch of high temps and low rainfall which followed a period of heavy rain, meaning the potential for standing water is high and the environment for [West Nile Virus] vector mosquito breeding is right,” said Tomek.

Tomek said the mosquitoes that carry West Nile Virus lay eggs on top of stagnant standing water, so residents should eliminate standing water from places such as old tires, clogged gutters, trash cans, wheelbarrows, buckets, watering cans and any other receptable that can hold water.

“These species do not travel far from the water they came from, so less sources of standing water on a person’s property decreases the risk even more in the direct area,” said Tomek.

If the risk of West Nile Virus become elevated, “minimizing time outdoors at dusk is recommended,” said Tomek. If outdoors at dusk, DEET or other insect repellents, used according to the manufacturer’s instructions, in addition to loose fitting clothes with long sleeves and pants can limit the amount of mosquito bites.

Tomek also recommends checking and repairing window screens, window air conditioners, dryer vents, doors, and other openings to limit ways mosquitoes can enter a residence.

Dead birds can be reported at the following website:

Finally, Tomek said that West Nile Virus vector mosquitoes are not to be confused with the floodwater nuisance mosquitoes that have been seen following the recent rain.

“West Nile Virus vector mosquitoes are known to be ‘quiet biters,’ often going unnoticed,” said Tomek.

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