While the risk of West Nile virus remains low in Rock County, the number of mosquitoes will be increasing given the time of year, recent rains and hot weekend forecast.
“With COVID-19 workloads, our mosquito surveillance program has taken a bit of a back seat during 2020 and 2021,” Rock County Public Health Department Environmental Health Director Rick Wietersen said. “We are in the process of starting up some surveillance later this summer. Some general observations are that the mosquito populations have started out slower than usual this year due to the dry spring, however the recent rains and upcoming hot weather later this week are ideal for mosquito breeding and it is likely that we will start to see a significant increase in mosquito population over the next couple of weeks.”
Wietersen said West Nile virus activity has been low in Rock County in recent years. There have been no reports of human cases of WNV in Rock County in the past two years. In Wisconsin, there were four confirmed human cases in 2020 with the closest being a case in Walworth County. There were two confirmed human cases of WNV in Wisconsin in 2019.
The Wisconsin Department of Health Services has discontinued the dead bird reporting hotline. Birds are susceptible to WNV and are often used as an indicator to help determine the prevalence of the virus in an area.
Hot weather with some potential rain is on the way. A few storms will be possible today into tonight, though most places will remain dry. The chance for storms will then return early next week. Heat indices are expected to be between 90 and 95 degrees over the weekend into early next week, according to the National Weather Service.
The time of year when mosquitoes are most active and most likely to carry the disease is between July and September, but if the weather remains warm, the risk period can extend as late as November. The mosquito, specifically the culex genus, are known for spreading WNV. These particular species of mosquito thrive when temperatures are high and precipitation is low, according to the Winnebago County Health Department.
Individuals with healthy immune systems, 80% of the public, who are bitten by an infected mosquito will usually not develop any symptoms of WNV. One in five individuals who are infected could develop mild flu-like symptoms including fever, headache, body aches, joint pain, vomiting, diarrhea or rash. Most people recover completely, but fatigue and weakness could last for weeks or even months in some individuals.