LAS VEGAS (FOX5) — A Clark County woman has been diagnosed with the first West Nile virus case of the year, health officials said.
The Southern Nevada Health District said the woman did not contract the virus locally. She traveled to another state with multiple cases of the virus.
Her case is neuroinvasive, according to the health district.
Louisa Messenger, a researcher at UNLV’s mosquito lab, said less than 1 percent of people with West Nile virus develop neuroinvasive cases. The virus crosses the blood-brain barrier and causes symptoms like meningitis and inflammation of the tissues of the brain.
“It can present clinically severe,” Messenger said.
Researchers monitor mosquito populations
UNLV’s mosquito lab collects mosquitoes from across the valley, particularly mosquitoes that can carry West Nile virus.
None of the mosquitoes collected has tested positive for the virus.
Messenger said her team is studying whether West Nile virus local to Las Vegas, is present in mosquitoes over winter.
“What we are interested in understanding is whether we have West Nile virus that is local to Las Vegas that is present in mosquitoes over winter, so essentially every transmission season we are getting the same type of virus affecting us year on year,” Messenger said.
Her team is waiting for samples from the current case to further their research.
Conditions favor mosquito activity
After a slow 2025 for mosquito season, this year is a concern for Southern Nevada health officials.
“We have had an unseasonably mild winter and the perfect conditions for mosquitoes to thrive. It was only a matter of time,” Messenger said.
She said summer temperatures so far this year are not hot enough to kill mosquitoes. People are spending more time outdoors, increasing exposure.
The virus comes from birds like crows and ravens. If they are infected, a mosquito can bite them and get the virus. The infected mosquito will then bite a human two to three days later, transmitting the infection.
Messenger said people should protect themselves with long-sleeve clothing and mosquito repellent.
The health district said there were no cases of the virus in 2025. In 2024, there were 26 cases.
Have a tip or story idea for Victoria? You can reach her at [email protected]
Copyright 2026 KVVU. All rights reserved.
