West Nile Virus Found in Los Angeles and Orange Counties

West Nile virus—a rare and serious disease that is transmitted through mosquitos—has made its way to Los Angeles and Orange counties, with several cases now confirmed throughout the region.

"Although the virus primarily affects birds, it gets transmitted to humans if a mosquito bites an infected bird and then bites a human," said Jonathan Grein, MD, director of Hospital Epidemiology at Cedars-Sinai. "Contracting a virus found in birds sounds like science fiction, but that's exactly what West Nile virus is."

While a single mosquito bite can be enough to transmit the infection, Grein said most people are not at risk following a single mosquito bite. In fact, Grein said, only a small number of people will develop the virus' most severe symptoms.

"Most people infected with West Vile virus will experience symptoms similar to the flu, including fever, headaches, muscle aches and fatigue," said Grein. "Although some people may develop a rash, abdominal pain, nausea or diarrhea, most experience only mild symptoms that last several days to weeks and resolve on their own."

Only about 1 in 150 people who contract West Nile virus will require hospitalization for severe symptoms, which can include coma, neck stiffness, high fever, paralysis and infection of the brain called encephalitis.

West Nile virus can occur in anyone, although certain people are at higher risk of developing the severe disease—including adults over the age of 50 and those with a weak immune system, such as patients on immune-suppressing medications like chemotherapy.

"It's also important to note that West Nile virus cannot be spread through touching, kissing or sharing utensils," Grein said. "The disease can only be transmitted through mosquito bites."

There is no vaccine available to prevent West Nile virus, so Grein said residents should protect themselves by following guidelines set by the Centers for Disease Control and Prevention.

Those guidelines include:

• Use insect repellent containing DEET—a known insect repellant—when outdoors. If you spray your clothing, there's no need to spray repellent on your skin.
• When possible, wear long-sleeved shirts and long pants treated with repellents containing DEET, since mosquitoes can bite through thin clothing.
• Consider staying indoors at dawn, dusk and in the early evening. These are peak hours for mosquito bites, especially those mosquitoes that carry the West Nile virus.
• Limit the number of places for mosquitoes to lay their eggs by getting rid of standing water sources from around your home, such as wading pools and planters.

"These standing water sources can include things like containers, planters and animal water bowls," said Grein. "It's important to take inventory of your outside area and remove any unnecessary items. This quick but impactful step may prevent the spread of West Nile virus."

Learn more about West Nile virus and how to prevent it, including recommendations from the American Academy of Pediatrics on using insect repellent on children.

Read more on the Cedars-Sinai blog: Am I Still Contagious?