As we enter mosquito season, the Illinois Department of Public Health (IDPH) is reminding Illinoisans of the diseases mosquitoes carry and the best ways to avoid being bitten.
“Each year since 2002 when we saw the first human cases of West Nile virus in Illinois, we’ve seen the virus circulate across the state,” said IDPH Director Nirav D. Shah, M.D. J.D. “This year many people are concerned about a relatively news virus – Zika virus. While Zika virus is also primarily transmitted through the bite of a mosquito, the main type of mosquito that carries Zika virus is different and is rarely found in Illinois. However, taking some simple precautions can help you avoid mosquito bites, regardless of the type of mosquito or the diseases they carry.”
West Nile virus is transmitted through the bite of an infected Culex pipiens, “house” mosquito. Mild cases of West Nile virus infections may cause a slight fever or headache. More severe infections are marked by a rapid onset of a high fever with head and body aches, disorientation, tremors, convulsions and, in the most severe cases, paralysis or death. Symptoms usually occur from three to 14 days after the bite of an infected mosquito. However, four out of five people infected with West Nile virus will not show any symptoms. People older than 50 are at higher risk for severe illness from West Nile Virus.
Zika virus is primarily transmitted through the bite of an Aedes aegypti mosquito, a mosquito that is rarely found in Illinois. The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting for several days to a week after being bitten by an infected mosquito. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika virus. For this reason, many people might not realize they have been infected. However, Zika virus infection during pregnancy can cause a serious birth defect called microcephaly, as well as other severe fetal brain defects. More information about Zika virus can be found on the IDPH website.
Predicting how bad the mosquito season will be is like predicting the weather – it can change week to week. The key factors in determining high or low levels of mosquito activity are temperature and rainfall. Although people usually notice mosquitoes during rainy conditions, those mosquitoes are commonly called floodwater or nuisance mosquitoes (Aedes vexans) and typically do not carry disease. In hot, dry weather, mosquitoes that carry West Nile virus breed in stagnant water, like street catch basins and ditches, and multiply rapidly. Similarly, the type of mosquito that carries Zika virus also breeds in stagnant water like empty flower pots, tires, and any container that holds water that is not changed weekly. There are two other types of mosquitoes (Aedes albopictus and Aedes triseriatus) found in Illinois that can also carry disease and breed in water-collecting containers.
There are some simple precautions you can take to reduce the number of mosquitoes around your home and protect yourself from being bitten. Precautions include practicing the three “R’s” – reduce, repel and report.
- REDUCE – make sure doors and windows have tight-fitting screens. Repair or replace screens that have tears or other openings. Try to keep doors and windows shut.
Eliminate, or refresh each week, all sources of standing water where mosquitoes can breed, including water in bird baths, ponds, flowerpots, wading pools, old tires, and any other containers.
- REPEL – when outdoors, wear shoes and socks, long pants and a long-sleeved shirt, and apply insect repellent that contains DEET, picaridin, oil of lemon eucalyptus or IR 3535, according to label instructions. Consult a physician before using repellents on infants.
- REPORT – report locations where you see water sitting stagnant for more than a week such as roadside ditches, flooded yards, and similar locations that may produce mosquitoes. The local health department or city government may be able to add larvicide to the water, which will kill any mosquito eggs.
Additional information can be found on the IDPH website.