SNHD confirms five more cases of West Nile virus

Researchers at the Southern Nevada Public Health Laboratory test mosquitoes for virus. (Photo courtesy of Southern Nevada Health District)

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The Southern Nevada Health District has confirmed five new cases of West Nile virus, bringing the total to seven, amid a major increase in mosquito activity.

Three patients — a female over the age of 60, and two males under the age of 50 — were diagnosed with a more serious form of the illness, a neuroinvasive form that can cause inflammation of the brain and spinal cord, leading to paralysis or a coma. All three patients were hospitalized and are still recovering, according to local health officials.

Two more patients — a male and female, both under the age of 50 — developed a milder form of the illness that often presents with symptoms similar to the common flu, including fever, headache, nausea, vomiting, and fatigue. Health officials report both patients have recovered.

Last week, two patients were diagnosed with West Nile virus in Southern Nevada. One of the patients, a male over the age of 70, was also diagnosed with the neuroinvasive form.

The additional confirmed cases this week come after health officials in Clark County reported the highest level of mosquito activity in the agency’s 20-year history of monitoring this month.

As of June 27, about 8,600 mosquitoes from 36 zip codes tested positive for West Nile virus. That is a significant increase from the 7,500 mosquitoes from 30 zip codes that tested positive for West Nile virus a week ago.

Mosquitoes in another six zip codes tested positive for the virus that causes St. Louis encephalitis, a vector borne virus that can result in flu-like symptoms or, in more severe cases, a neuroinvasive form of the disease that can cause paralysis or a coma.

Local health officials warn that the increase in mosquitoes positive for West Nile virus could lead to a major spike in cases. Mosquito season in southern Nevada typically lasts from June to October, meaning there is potential for cases to rise in the coming months.

There is precedent in Nevada for a spike in locally-transmitted West Nile virus. In 2019, the health district confirmed 43 cases of the illness in patients after mosquitoes tested positive for the virus across 43 zip codes.

Clark County does not fund a dedicated mosquito control program to oversee the treatment and elimination of mosquito breeding by removing mosquito habitats, and deploying pesticides to eliminate adult mosquitoes and mosquitoes at the larval stage.

However, the county announced the purchase of a $68,000 drone last week, capable of spraying pesticides in large areas of standing water, flood channels, and detention basins across the county. The county plans to use the drone — which can carry up to 50 pounds of pesticide and fly for about 30 minutes at a time — to deploy a larva-killing bacterial pesticide.

Mosquito abatement programs in the U.S. have proven effective at reducing mosquito populations. The Centers for Disease Control and Prevention warns that the only way to reduce mosquitoes and the dangers they pose is a comprehensive hands-on approach , including monitoring, targeted pesticide use, and systemic interventions by local governments.

Public health officials are encouraging everyone to take steps to protect themselves. The risk of mosquito-borne illnesses can be reduced by eliminating standing water around homes, and installing protective screens on doors, windows, and doggy doors.

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