On Friday, the Southern Nevada Health District (SNHD) reported that some mosquitos found in the 89031 and 89032 zip code tested positive for West Nile Virus (WNV).
The Aedes aegypti mosquitoes have reportedly increased significantly in number since they were reported in Clark County in 2017, according to SNHD.
The SNHD states they have identified the first West Nile virus-positive mosquitoes of the season. In their alert, they reported the following:
Since starting its seasonal mosquito surveillance on April 1, Health District staff have set more than 875 traps to survey mosquito quantity, species and infected mosquitoes. Traps are placed at parks, wash channels, wetland areas, residential communities and other potential breeding sites. Captured mosquitoes are taken to a laboratory at the Health District’s Main Public Health Center, where they are sorted and cataloged by species and location. The samples are then sent to the Southern Nevada Public Health Laboratory to test specimens for harmful arboviruses. To date, more than 9,000 mosquitoes have been tested this year.
West Nile Virus, a mosquito-borne disease, reached unprecedented activity in Clark County in 2019, with 43 human cases. In contrast, there was minimal activity in 2020, 2021 and 2022. Two human cases of West Nile Virus were reported in 2023.
National Mosquito Control Awareness Week begins June 20-26 and the SNHD is reminding residents of the Fight the Bite campaign to minimize exposure and illness.
Monsoon weather and flooding can bring mosquitos to local areas.
According to the CDC, West Nile virus is the leading cause of mosquito-borne disease in the continental United States.
CDC data for 2024 is not yet available. However in 2023, the CDC reports there were 47 cases. Two cases had been reported in Nevada last year, however currently no cases have been reported this year.
What is West Nile virus?
West Nile virus was originally discovered in the 1930’s in the West Nile district of Uganda. It is believed to have reached the United States in the late 1990’s.
It’s in the family of Flaviviridae in which the disease is vector transmitted, such as by ticks, or mosquitoes, and can infect mammals as hosts. West Nile is in the same family as Zika, Yellow Fever, Dengue Fever, and Japanese Encephalitis.
Culex genus/species of mosquitoes are the usual culprit. They feed from evening to morning, hence are more active during those times.
How is West Nile transmitted?
A mosquito contracts the disease while feeding on an infected bird and then can transmit it to humans.
What are the symptoms of West Nile virus infections?
80% of those infected do not exhibit symptoms. Some however, may elicit the following if they have mild illness:
- Fever
- Body aches
- Fatigue
- Nausea
- Vomiting
- Joint pains
- Weakness
- Rash
Rarely (1 in 150 people) may become seriously ill with neuroinvasive symptoms. These include:
- Headache
- Neck pain/Stiff neck
- High fever
- Sensitivity to the light (photophobia)
- Tremors
- Weakness
- Paralysis
- Confusion
- Disorientation
- Seizures
- Coma
- Death
Since mosquitoes are the primary vector, avoiding them is paramount to limiting infection. We recommend the following:
Clean up areas of standing water around the house such as kiddie pools, puddles, and buckets as they provide a breeding ground for mosquitoes.
Wear light long sleeve clothing, and pants tucked into socks/shoes when outside.
Use DEET or insect repellent that can also be sprayed onto clothes when planning to be outdoors.
Be aware that many mosquitoes are active from dusk till dawn.
If bit by a mosquito, contact your local medical provider if you have any of the aforementioned symptoms.
Dr. Daliah 
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