Mosquito and Vector Diseases


Knox County Health Department tests mosquitoes and dead birds for West Nile virus, in conjunction with the Illinois Department of Public Health. West Nile Virus is the most common illness caused by mosquitoes in Illinois. 

West Nile Virus Disease Symptoms

West Nile Virus is a disease that can cause inflammation in the brain. Most people who are infected with West Nile Virus will have no symptoms.  Symptoms may include headache, body aches, joint pain, vomiting, diarrhea, or a rash. Most people with mild illness will recover completely but may experience fatigue or weakness weeks after infection.  Severe infection will usually begin with a high fever, followed by body aches, disorientation, tremors, and in the most severe cases, death. West Nile Virus is only transmitted through mosquitoes. You cannot catch West Nile Virus from contact with a sick person.

West Nile Virus Surveillance

The Illinois Department of Public Health, in partnership with most local health departments, including Knox County Health Department, conducts West Nile Virus surveillance from May through October. This includes testing mosquitoes and dead birds, which can carry West Nile Virus and infect mosquitoes.

Knox County Health Department can submit the following birds for West Nile testing from May to September:

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  • Crows
  • Blue Jay
  • Grackle
  • Starling
  • Robin
  • Finch
  • Sparrow
  • Cardinal
  • Swallow
  • Flycatcher
  • Cat bird
  • Mockingbird
  • Warbler
  • Wren

No waterfowl, large birds, or endangered birds will be tested.

If you would like to report a dead bird from the list above, please call the Knox County Health Department at 309-344-2224. Only birds that appear to have died from natural causes and are not decayed should be reported.

Additional West Nile Virus Information

For additional information or resources about West Nile Virus, please refer to the Illinois Department of Public HealthCenters for Disease Control and Prevention, or The American Mosquito Control Association.

Protect Yourself from Mosquito Borne Illness

Preventing bites

The best way to stay safe from all diseases spread by mosquitoes to avoid getting bitten. Reduce your risk of mosquito bites by:

Managing Mosquitoes

Mosquitoes breed in standing water. You can make sure mosquitoes do not have a place to breed by getting rid of standing water. Make sure that you store buckets upside down, change out bird bath water frequently, and report large areas of standing water to the Knox County Health Department.


West central Illinois has several species of ticks, some of which may carry disease. Ticks native to Illinois include, the American dog tick, the Blacklegged tick, the Brown dog tick, and the Lone star tick. For more information about the ticks found in west central Illinois, refer to the CDC’s regions where ticks live.

Ticks can spread diseases, such as Lyme Disease, Rocky Mountain Spotted Fever, Tularemia, Anaplasmosis, Babesiosis, Heartland Virus Disease, and Ehrlichiosis.

The best way to avoid diseases spread by ticks is to avoid tick bites. Check out the CDC’s tips to prevent tick bites.


While most bats do not carry rabies, there is a chance that a bat will be infected with rabies. You cannot tell if a bat has rabies just by looking at it. If you have been bitten by a bat, the bat must be tested for rabies. If someone wakes up in a room with a bat, you may not know if they have been bitten, so that bat should be tested for rabies.

Avoid all contact with the bat while catching it for rabies testing. If you feel safe doing so, you can catch the bat in a box, preferably while wearing leather gloves. Once the bat has been caught, please contact the Knox County Health Department at 309-344-2224, so the bat can be tested for rabies.