As West Nile Spreads, Officials Emphasize the Importance of Mosquito Control

As state and local health departments around the country continue to monitor areas of water for West Nile virus-positive mosquitoes, new human cases have health officials warning the public to take precautions against bug bites.

Since 1999, when West Nile virus was first detected in the United States, the Centers for Disease Control and Prevention (CDC) has been tracking the mosquito-borne disease each summer from June to September. In 2003, the United States saw its most severe West Nile virus season, with a reported 9,862 human cases that year alone. Since then, the country has seen as few as 712 cases in 2011, and as many as 5,674 cases in 2012. While individuals can minimize their risk of getting the virus by avoiding areas with West Nile-positive mosquitoes, eliminating standing water near their homes, using insect repellant, and wearing protective clothing outdoors during the dusk through dawn hours, public health officials practice vector control tasks to manage and eliminate areas with West Nile virus-positive mosquitoes.

Colorado’s Larimer County reported its first human case of West Nile virus this season on August 1, 2017. According to the Larimer County Department of Health and Environment, the virus was found in a blood donor who is a resident of Fort Collins. While the donor has shown no symptoms of the infection, local health officials say that all blood donations positive for the virus have been discarded and are not being used for blood transfusions. This is the second human case of West Nile virus in Colorado so far this season. The Colorado Department of Public Health and Environment notes that while West Nile cannot be spread from person-to-person, there have been cases of individuals getting the virus from blood transfusions, organ transplants, and from mother-to-baby during the birthing process. Humans most commonly get the virus from the bites of infected mosquitoes, which pick up the virus from infected birds.

With new human cases of West Nile being reported, health officials in areas such as Utah’s Utah County and Michigan’s Macomb County are on alert following new reports of West Nile-positive mosquitoes. While Utah County has tested 792 pools of mosquitoes in the area and found only 1 to be positive, the news serves as a warning of how easily the disease can spread to humans.

“While Utah County does not currently have any confirmed human cases of West Nile Virus, this is a great reminder to residents of the importance of taking steps to protect themselves from mosquitoes,” says Eric Edwards, MCHES, MPA, Deputy Director of the Utah County Health Department. In Michigan, although no human cases of West Nile have been reported so far this season, 2 separate samples from Macomb County mosquito pools recently tested positive for the virus, making the county the sixth so far in the state this season to report West Nile-positive mosquitoes.

In Philadelphia, which has seen 51 mosquito pools test positive for West Nile but has no human cases thus far, the local Department of Public Health’s Division of Disease Control is emphasizing the importance of mosquito control to prevent the spread of the virus. Local surveillance efforts have tested more than 700 mosquito pools so far this season, and the city’s health department has worked with the Pennsylvania Department of Environmental Protection to manage areas with West Nile-positive mosquitoes through the use of larvicide, ground spraying, and by eliminating breeding sites.