Three more Clark County residents have tested positive for West Nile virus, and the Southern Nevada Health District is reminding the public to take precautions to protect themselves from this potentially serious disease. One individual is a male over the age of 50 who had the non-neuroinvasive form of the illness, and another is a female under the age of 50 who had the neuroinvasive form of the illness. The third individual is a male over the age of 50 who was asymptomatic and is classified as a presumptively viremic donor (PVD). Because 80 percent of people infected with West Nile virus are asymptomatic, all potential blood donors are screened to reduce the risk of transmitting the virus through blood transfusions. The Health District has previously reported two cases of West Nile virus this year, both in females over the age of 50 with neuroinvasive disease. These three new cases bring Clark County’s 2019 case count to five.

The Health District’s Mosquito Surveillance Program continues to identify West Nile and St. Louis encephalitis virus-positive mosquitoes throughout Southern Nevada. West Nile virus-positive mosquitoes have been found in 25 unique ZIP codes and mosquitoes testing positive for the St. Louis encephalitis virus have been found in ten unique ZIP codes so far this season. More than 33,000 mosquitoes have been submitted for testing this year. Of those samples, 4,987 pooled samples have tested positive for West Nile virus, and 433 have tested positive for St. Louis encephalitis.

“Our mosquito surveillance activities are showing us that there is an outbreak of mosquito-borne diseases occurring right now in our community. West Nile virus and St. Louis encephalitis are being actively transmitted from infected birds to mosquitoes, which then places the public at increased risk for disease,” said Dr. Joe Iser, Chief Health Officer for the Southern Nevada Health District.

“The most effective way to keep from getting infected with West Nile virus and other mosquito-borne illnesses is to prevent mosquito bites,” said Iser.

The Health District is urging the public to use insect repellent, wear light-colored, long-sleeved shirts and pants, and to take steps to control mosquitoes in and around their home. Use Environmental Protection Agency (EPA)-registered insect repellants containing DEET, Picaridin, IR3535, Oil of lemon eucalyptus (OLE), or 2-undecanone. Eliminate areas of standing water, including non-circulating ponds, “green” swimming pools, and accumulated sprinkler runoff, which support mosquito breeding. For more tips, go to the Health District’s Mosquito Breeding Prevention website.

For additional information and weekly updates on the Health District’s mosquito surveillance activities go to:

Access information about the Southern Nevada Health District on its website: Follow the Health District on Facebook:, YouTube:, Twitter:, and The Health District is available in Spanish on Twitter: Additional information and data can be accessed through the Healthy Southern Nevada website: