First human case of West Nile Virus reported in Clark County

Clark County, Ohio – A Clark County resident has contracted West Nile Virus (WNV) and is believed to be the first individual to be infected in the state of Ohio this year, the Clark County Combined Health District (CCCHD) reports.

The female patient began showing symptoms August 13 that included fever, chills, headache, fatigue, nausea, and diarrhea. CCCHD works with the Ohio Department of Health (ODH) to identify probable cases of WNV.

An Ohio resident earlier this year is presumed to have contracted West Nile Virus, but the exposure occurred in Arizona. In this case, exposure to an infected mosquito is believed to have occurred in Clark County.

This is Clark County’s first human case of WNV reported since 2018 when two human cases were documented, and the fourth human WNV case since 2013.

Dozens of mosquito samples collected by CCCHD in the last four weeks have tested positive for West Nile Virus, and CCCHD reported August 10 that WNV-infected mosquitos were widespread throughout the area.

This week, seven more samples from all over the county were found to be positive. Those samples added to the growing list of WNV-positive mosquitos identified in Clark County in the last month.

Mosquitos sampled and collected throughout the county are submitted to the Ohio Department of Health (ODH) as part of our Vector-Borne Disease Program.

“With the number of positive West Nile Virus mosquito samples we have found, it is disappointing but not surprising to have a human case,” said Larry Shaffer, Director of Environmental Health. “The most effective mosquito control is for everyone to get rid of standing water at their homes to eliminate breeding sites. It’s also important to wear appropriate clothing and use an EPA approved repellent when outdoors in the early morning or evening.”

CCCHD advises residents to assume the presence of West Nile Virus in their area and to take steps now to eradicate mosquito habitats along their properties.

The best way to avoid the West Nile Virus infection is to prevent mosquito bites, and the best way to avoid being bitten by a mosquito is to eliminate habits where mosquitos can survive and reproduce.

CCCHD recommends a three-part strategy to combat mosquitos: AVOIDPLANSTOP:


  • Apply repellents on exposed skin registered with the U.S. Environmental Protection Agency (EPA.) 
  • Wear long sleeves and pants or consider staying indoors as much as possible. 


  • If traveling, check ahead of time for travel advisories, and plan accordingly. 
  • Have EPA approved mosquito repellent and longs pants and shirts available to avoid bites.
  • Do outside activities at times when mosquito activity is less.


  • Get rid of mosquito breeding sites by emptying or treating any standing water on your property (even small amounts of standing water can be a breeding site for mosquitos.)  
  • Make sure screens on windows and doors are free of holes or rips. You may also opt to utilize air conditioning instead of open windows if possible.

Residents’ cooperation in getting rid of standing water is the most effective means of reducing the total number of mosquitos and far more effective that spraying. 

In response to the confirmed presence of West Nile Virus, CCCHD is: 

  • Inspecting the affected area and working with property owners to reduce breeding sources by draining stagnant water or treating stagnant water with products containing Bacillus thuringiensis israelensis (Bti.) Bti is safe for humans and pets and only affects the mosquito larvae. 
  • Misting the affected area with Duet® to reduce the adult mosquito population when weather permits. While safe for humans and pets, residents who have a concern about misting may opt out by calling 937-390-5600 or emailing the request and their address to [email protected]
  • Continuing to monitor the area for West Nile Virus.

West Nile Virus is most commonly spread by infected mosquitoes and can lead to severe fever, encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord.) 

The primary vector in Ohio is the northern house mosquito, Culex pipiens. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread the virus to humans and other animals when they bite.

Approximately 80 percent of people who are infected with WNV will not show any symptoms at all, but there is no way to know in advance if you will develop an illness or not. Those who develop symptoms usually do so between three to 14 days after they are bitten by the infected mosquito. There is no specific treatment for WNV infection, and care is based on symptoms.

About one in 150 people infected with WNV will develop severe illness.  The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.  These symptoms may last several weeks, and neurological effects may be permanent.

Up to 20 percent of people who become infected will have symptoms that can include fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands or a skin rash on the chest, stomach and back.  Symptoms can last for a few days or up to several weeks. 
For more information contact the CCCHD at 937-390-5600 or go to our website at