/Health District reports second human West Nile case

Health District reports second human West Nile case

August 31, 2017

LAS VEGAS – The Southern Nevada Health District is reporting the second case of West Nile virus in a Clark County resident in 2017. The individual, a female over the age of 50, has the more serious neuroinvasive form of the illness. The county’s first case of West Nile virus was reported in May. The patient, a male over the age of 50 died from the illness. The Health District does not provide additional information regarding individual cases. There were two reported West Nile cases and three cases of St. Louis Encephalitis, a similar mosquito-borne illness, in 2016.

“An additional report of serious illness serves as a reminder to our community of the importance of taking precautions against mosquito bites,” said Dr. Joe Iser, Chief Health Officer for the Health District. “Mosquitoes are still quite active in Southern Nevada. We urge everyone to take simple steps to eliminate mosquito breeding sources around their homes to protect themselves, their families, and communities.”

The Health District’s Mosquito Surveillance Program tests mosquito pools for West Nile virus, St. Louis Encephalitis, and Western Equine Encephalitis. This season, 1,763 mosquito traps have been set, and 40,801 mosquitoes submitted to the Nevada Department of Agriculture Animal Disease Laboratory for analysis. The program has identified 14 ZIP codes in Clark County with West Nile virus-positive mosquito pools. St. Louis Encephalitis-positive and Western Equine Encephalitis-positive mosquito pools have also been identified in one ZIP code each within Clark County. The program also conducts surveillance for Aedes aegypti mosquitoes, the species that can transmit Zika and other viruses. This species was identified in Clark County this season. To date, none have tested positive for Zika.

Travel precautions and preventive measures have been stressed due to the threat of Zika virus. However, West Nile virus cases are reported throughout the continental United States. It is important to practice preventive measures against mosquito bites both at home and when traveling, whether a destination is within the state, to a neighboring state, or to an international destination.

West Nile virus is spread through the bites of infected mosquitoes that have acquired the virus by feeding on infected birds. The illness is not spread person to person. Many people with the virus will have no symptoms or very mild clinical symptoms of illness. Mild symptoms include fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach, and back. In some cases, the virus can cause severe neurologic illness and even death.

The Health District recommends the following to prevent mosquito bites and to eliminate breeding sources:

  • Use Environmental Protection Agency (EPA)-registered insect repellents containing DEET, Picaridin, IR3535, Oil of lemon eucalyptus (OLE), or 2-undecanone.
  • Wear pants and long-sleeved shirts to reduce mosquito exposure when outdoors.
  • Eliminate areas of standing water around your home, including non-circulating ponds, “green” swimming pools, and accumulated sprinkler runoff, which support mosquito breeding.

Additional prevention tips are available on the CDC’s Prevent Mosquito Bites webpage.

Travel associated cases of the Zika virus have been reported in Clark County residents, as well as one case that was sexually transmitted. The Zika virus can also be spread from a mother to her baby during pregnancy. Infection during pregnancy can cause a birth defect called microcephaly and other severe fetal brain defects. The Health District has reported two cases of travel-related Zika virus in 2017. Updated information on case reports is available at Zika Virus Disease Updates.

For more information on Zika virus, travel precautions, and special precautions for pregnant women, visit the CDC’s Zika Virus website. Go to the Health District’s Mosquito Surveillance webpages for information about surveillance activities, prevention tips, and more. For additional information on eliminating breeding sources, access the CDC’s Controlling Mosquitoes at Home webpage.


The Southern Nevada Health District serves as the local public health authority for Clark County, Boulder City, Henderson, Las Vegas, Mesquite and North Las Vegas. The agency safeguards the public health of the community’s residents and visitors through innovative programs, regulations, and initiatives focused on protecting and promoting their health and well-being. More information about the Health District, its programs, services, and the regulatory oversight it provides is available at www.SNHD.info.