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West Nile virus found in San Diego

By The Health News Team | September 14, 2023
Person in the woods putting on bug spray

The West Nile virus is not something you’re likely to worry about. That is, unless you’ve heard about the person in Placer County who was recently infected, or the dead crow found in La Mesa and mosquitoes collected in North County that tested positive for the virus.

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. And about 1 out of 150 infected people develop a serious illness that can lead to death.

Locally, the crow found in La Mesa is the first dead bird to test positive for the virus this year, the County of San Diego reports. There have not yet been any human West Nile virus cases reported in San Diego in 2023. However, six county residents infected with WNV died in 2015.

“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 is also important 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

“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.”

Learn more about family medicine; get the latest health and wellness news, trends and patient stories from Sharp Health News; and subscribe to our weekly newsletter by clicking the "Sign up" link below.

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