West Nile Virus: An Early Start to the Season?

State health officials around the country are reporting additional mosquito pools testing positive for West Nile virus along with new human cases, in what some officials are saying may be an early start to the season for the arbovirus.

In the United States, West Nile virus activity typically begins in June and lasts through September; this time period is when mosquitos are most active in the lower 48 states. The Centers for Disease Control and Prevention (CDC) reports that in 2016 the number of human cases of the virus in the United States peaked in the month of August, while in the previous year, the human case count peaked in early September. After first appearing in the United States in 1999, the number of human West Nile cases surged in 2003 to 9,862 infections spanning 45 states, and last year, the CDC reported a total of 2,038 cases in 47 states. Through vector control, improved surveillance of mosquitos, and local efforts to remove standing water, state and federal health officials each season continually strive to reduce the number of mosquito bites, and thus, prevent new cases of the virus.

Kansas is reporting its first human case of West Nile this season in Barton County, with Kansas Department of Health and Environment (KDHE) officials noting that this may indicate an earlier start to the season. The news accompanies the discovery of new mosquito pools that have tested positive for West Nile virus in the following counties: Reno, Shawnee, and Johnson. Furthermore, officials report that two birds have tested positive for the virus in Shawnee county. A recent press release issued by the KDHE, shared that last year, Kansas reported 34 human cases of West Nile, which led to 21 hospitalizations and 5 deaths. With the new surveillance findings, state health officials warn that the public should look out for telltale symptoms of the virus, which include headache and fever. They also are reminding the elderly or immunocompromised individuals to limit their time outdoors during the dawn to dusk hours, when the Culex species mosquitoes that transmit West Nile tend to be most active.

In Pennsylvania’s Lackawanna and Cumberland counties, officials have reported new findings of mosquitoes testing positive for West Nile virus. To date, 8 Pennsylvania counties have detected the virus in mosquito samples; however, no avian or human cases have been reported so far. In Scranton, where one of the recent West Nile-positive mosquito samples were found, an health official noted in a local news report that the detection of the virus is occurring about a month earlier than usual for the area, pointing out that West Nile virus typically begins to appear in mid-July. The state reported 16 human cases of West Nile virus in 2016, which occurred between July and November.

As additional reports of West Nile-positive mosquitoes continue to spring up in parts of Ohio, Missouri, Illinois, and other states, health officials continue to remind residents to limit their exposure to mosquitoes by using insect repellants, keeping windows shut or screened, removing standing water from their properties, and avoiding outdoor activities during the hours when mosquitoes are most active.