Mosquitoes in Fox River Grove test positive for West Nile virus

First batch in McHenry County to test positive for the virus, which can cause serious illness

A batch of mosquitoes collected in Fox River Grove earlier this month tested positive for the West Nile virus, the McHenry County Department of Health reported.

This batch, collected July 13, is the first of 260 tested by the health department to come back positive for the virus.

The West Nile virus can cause serious illness, especially among people age 60 and older, according to a news release. It is not unusual for mosquitoes to test positive for West Nile this time of year, and the risk typically remains until the first hard frost.

So far in 2021, the Illinois Department of Public Health has reported no human cases but has identified 92 positive mosquito batches statewide. Last year, the IDPH identified 39 cases in humans, including four that resulted in death.

Those who contracted the virus last year ranged in age from 29 to 84, with a median age of 63, according to state data.

Illness from the West Nile virus usually is mild and includes a fever, headache and body aches. Serious illnesses, such as encephalitis, meningitis and death, are possible. People age 60 and older have the highest risk of serious illness.

The West Nile virus is transmitted to humans primarily through the bite of culex mosquitoes, according to the release. There is no vaccine available for the virus.

Infected birds can become carriers of the virus through the bite of an infected mosquito before passing it on to other mosquitoes that feed on them.

The best way to prevent West Nile is to reduce the number of mosquito breeding sites and to take personal precautions.

The county recommends that people:

  • Empty standing water from containers around the yard, such as tires, neglected swimming pools, birdbaths, clogged gutters and buckets
  • Make sure doors and windows have tight-fitting screens.
  • Limit outdoor activities when culex mosquitoes are most active – particularly dusk and dawn – and wear long-sleeved shirts and long pants for extra protection
  • Use and apply insect repellents according to the directions on the label

Insect repellents containing 20% or more DEET are effective, but smaller concentrations are better for children, according to the McHenry County health department, and a doctor should be consulted before using any repellant on infants. Insect repellents, including the oil of lemon eucalyptus or Picaridin, can be used as an alternative to DEET.