Swarms of Mosquitoes With West Nile Virus Surround Las Vegas

Swarms of potentially deadly mosquitoes are surrounding Las Vegas, and local officials are warning people that it may not be the best time to visit the city.

According to local health officials, Southern Nevada is experiencing its highest level of mosquito activity on record and more than 3,000 of the deadly insects have tested positive for West Nile virus already.

In a press release sent out on Monday, the Southern Nevada Health District said that, as of June 6, there have been 91 pools of mosquitoes that have tested positive for this virus. The total number of mosquitoes is 3,081, and they have been found in 16 different Zip codes.

Two separate pools, which total 46 mosquitoes across two other Zip codes, have also tested positive for a virus that results in St. Louis encephalitis.

The health district has a Mosquito Surveillance Program, and it’s recently received an increase in the number of complaints it has received from residents regarding mosquito activity, the press release pointed out.

The rise in these reports was attributed at least in part to the fact that Aedes aegypti mosquitoes in the region have increased recently. This type of mosquito aggressively bites humans during daytime, and tends to flock toward people instead of birds.

The press release also pointed out that this type of mosquito tested positive for West Nile virus recently, and that’s the first time in the history of Clark County, of which Las Vegas is a part.

In the last four years, this part of the state has experienced minimal activity for West Nile virus, according to state health officials. In 2023, only two cases of the virus in humans were reported. There were 43 confirmed cases in humans reported in 2019.

Humans can become infected with the deadly virus if they’re bitten by a mosquito that is also infected. About 20% of people who are infected with this virus experience symptoms including headache, fever, body aches, diarrhea, rash and/or vomiting.

Roughly one in 150 people who are infected develop much more serious symptoms, and the virus can even be fatal.

The last time a Clark County mosquito tested positive for the virus that causes St. Louis encephalitis was in 2019. The press release pointed out that no human cases have been reported since 2016.

This virus also spreads to humans through a mosquito bite. Most people who end up getting infected don’t develop any symptoms at all, though some develop a headache, fever, vomiting, fatigue and nausea. 

Others could develop a neuroinvasive form of the disease that either causes encephalitis — or inflammation of the brain — or meningitis — or inflammation of membranes that surround the spinal cord and brain.

The public should take preventative steps to protect themselves from mosquito bites, health officials said. This includes ensuring there is no standing water on their property, as that can serve as a breeding ground for mosquitoes. 

Insect repellant can also be effective at preventing bites.