West Nile virus found in San Diego

The West Nile virus is not something you’re likely to worry about. That is, unless you’ve heard about the San Diego resident who recently tested positive for the mosquito-borne illness.

According to the Centers for Disease Control and Prevention (CDC), the West Nile virus (WNV) is the No. 1 cause of mosquito-borne disease in the U.S. While most people infected with WNV do not have any symptoms, about 1 in 5 people develop a fever and other symptoms. About 1 out of 150 infected people develop a serious illness that can lead to death.

Locally, the County of San Diego confirmed the first positive WNV case of the year in a man, age 71. He had recently traveled to rural Colorado, where he likely contracted the virus, and was hospitalized in San Diego.

Although WNV is rare in San Diego, county medical officials report it is present. In September, a dead bird found in Clairemont tested positive for the disease.

“When we have climate change, we have warmer temperatures, which leads to heavy rainfall,” says Dr. Abisola Olulade, a board-certified family medicine doctor with Sharp Rees-Stealy Medical Group. “So, we see more mosquitoes, which are potentially carrying vector borne illnesses, like West Nile virus. We have seen increased cases of the virus in California, and it’s concerning.”

How West Nile virus is transmitted

Most people are infected with WNV by a mosquito bite. Mosquitos are infected by feeding on dead birds with WNV. Unlike common viruses now circulating, such as flu, COVID and RSV, West Nile virus is not spread through coughing, sneezing or touching.

Although most people infected with WNV will have no symptoms or very mild symptoms, about 1 in 5 people will experience symptoms such as:

• Fever

• Headache

• Body aches

• Joint pains

• Vomiting

• Diarrhea

• Rash

These mild symptoms are usually treated with over-the-counter pain medications, such as Tylenol and Advil, and anti-vomiting and diarrhea medications, such as Kaopectate and Pepto-Bismol. Rest and fluids — water, tea, electrolyte solutions and sports drinks — are also helpful. Additionally, itchiness at the site of the bite can be easily treated at home.

“The first step if you see bites on the skin is to make sure that you wash the area with mild soap and water,” Dr. Olulade says. “To reduce the redness and itching, you can put ice on the bite or use topical cortisone or antihistamine creams. If you want a more natural remedy, you can use baking soda. Just add a bit of water to the baking soda, create a paste, add it to the bite, let it sit for a while, and then wash it off.”

Some people infected with WNV — about 1 in 150 — develop severe symptoms affecting the central nervous system. These can lead to hospitalization or death.

Symptoms of severe illness include:

• High fever

• Headache

• Neck stiffness

• Stupor

• Disorientation

• Coma

• Tremors

• Convulsions

• Muscle weakness

• Vision loss

• Numbness

• Paralysis

Preventing the spread of West Nile virus

Because WNV is most commonly spread through mosquito bites, the best course of action is to take measures to ensure you’re not bitten. The CDC recommends using insect repellent; wearing long-sleeved shirts and pants; treating clothing and gear with repellant; and taking steps to control mosquitoes indoors and outdoors.

Environmental Protection Agency (EPA)-registered insect repellents are known to be safe and effective, though it is important to read labels for instructions as well as guidance on their use in young children. EPA-registered repellents include:

• DEET

• Picaridin

• IR3535

• Oil of lemon eucalyptus (OLE)

• Para-menthane-diol (PMD)

• 2-undecanone

To control mosquitos, the CDC advises using screens on all windows and doors and avoiding allowing water to stand. Once a week, empty and scrub, turn over, cover or throw out items that hold water. This includes tires, buckets, planters, toys, pools, birdbaths, flowerpots and trash containers.

You can also use larvicides, which are insecticides that kill mosquito larvae and pupae before they can grow into biting adults. Adulticides, which kill adult mosquitoes, can be applied where mosquitos gather, such around plants, leaves, dense brush and tall grasses; under the eaves on buildings, decks and porches; and in moist, shady areas. Always follow label instructions or hire a pest control professional to treat your outdoor areas.

It's also essential to report increased mosquito activity; stagnant, green swimming pools; other mosquito-breeding sources; and dead birds to local authorities. In San Diego County, you can call the Vector Control Program at 858-694-2888 or email vector@sdcounty.ca.gov.

“The most important thing to remember is that if you think you were bitten by a mosquito and have a high fever, neck pain or other signs of serious illness, you should immediately reach out to your doctor,” Dr. Olulade says. “If it is a severe case, you may need to be hospitalized to receive supportive treatment, such as IV fluids, pain medication and symptoms monitoring.”

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