The department said in July that the first mosquitoes of the year had tested positive for eastern equine encephalitis virus.
The virus was found as a result of a, "massive mosquito surveillance project conducted by the environmental health division at the Kent County Health Department".
West Nile is an illness that can be deadly for people with weakened immune systems, and the elderly, according to the health department.
The traps, known as Gravid traps, were placed in the 49503, 49504, 49507 and 49519 zip codes in early June.
Exeter Hospital evacuated after reports of odor, several ambulances respond to scene
Fire crews were dispatched to the hospital, and both the emergency room and operating room areas were evacuated and closed. A union leader says multiple ambulances are making their way to the hospital for a report of a "mass casualty incident".
"The fact that we have found West Nile in only one area does not mean that it is confined to that ZIP code", says Adam London, Administrative Health Officer with KCHD. The county also set four traps that attract the kind of mosquitoes that carry the Zika virus: Aedes Egypti and Aedes Albopictus mosquitoes.
"We want people to be aware that they can greatly reduce their own risks by taking some simple precautions", he said in the release.
The first MI case of West Nile was diagnosed in 2001, two years after it appeared in the United States.