The Mosquito and West Nile Virus

Although mosquito-borne disease is rare in Illinois, mosquitoes can carry at least three encephalitis viruses that can cause human disease. In 2001, West Nile virus (WNV) was detected for the first time in Illinois in birds, horses, and mosquitoes. West Nile virus causes encephalitis primarily in older adults.

For more information regarding Vector  Control and Surveillance in Illinois, follow please visit

Southern Illinois tick chart

The Disease Cycle

Arboviral encephalitis is an inflammation of the brain caused by arboviruses (viruses carried by arthropods, such as mosquitoes and ticks). Other forms of encephalitis can be caused by other types of viruses and bacteria. In Illinois, arboviruses are primarily transmitted to humans by the bites of infected mosquitoes. (read more)

Mosquitoes transmitted infection chart

Lyme Disease & Rocky Mountain Spotted Fever

Ticks are a common pest that are encountered in the outdoors. Ticks are very efficient carriers of disease because once attached, they may go unnoticed for a period of time while they feed on their host. Ticks are commonly found on grass, weeds, and shrubs and will wait until a host moves by, when they will let go and climb onto the host. Ticks become more active when ground temperatures reach 40 degrees F, with peak activity occurring in the late spring and early summer months.

Ticks are found in two groups: “hard” ticks and “soft” ticks. As their name implies, hard ticks have a hard shield and are shaped like a flat seed when unfed. Soft ticks lack the hard shield and are shaped like a large raisin. The soft ticks generally feed on birds and bats.

Of the at least 15 species of ticks found in Illinois, only a few are likely to be encountered by people. Those species include: American dog tick, lone star tick, blacklegged (deer) tick, brown dog tick, and winter tick. 

Tick size chart


Miranda Adams,
Environmental Health Director
Administrative Office
Phone: (618) 634-2297 ext: 973114​

37 Rustic Campus Dr. Building C
​Ullin, IL 62992

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