I just read that there’s a new mosquito virus being found in Florida that can harm the brain. What is it? I thought Zika was the one we’re worried about.



Parasitic mosquitoes may seem to be relatively harmless compared to the vicious or venomous predators of the world, but the diseases they carry kill more human beings than any other animal. They spread an array of diseases that result in more than 700,000 deaths worldwide annually. With 3,000 known mosquito species — about 175 of them here in the U.S.

{¶}— it’s no surprise that new mosquito-borne illnesses keep making news.

The virus you’re asking about is the Eastern equine encephalitis virus, or EEEV. In July, health officials in Florida reported finding the virus in horses, chickens and other animals across the state, prompting a statewide alert.

Symptoms, which appear from three to 10 days after infection, come on quite suddenly. They include headache, which becomes progressively more severe, fever and body aches. The virus is fatal in about one-third of patients and puts survivors at risk of ongoing neurological problems. The virus can lead to encephalitis, which is inflammation and swelling of the brain.

Signs that the virus has begun to affect the brain include loss of muscle control, weakness or paralysis; changes to sensation, including tingling or numbness; decline in cognitive function; and the onset of seizures. There is no human vaccine for the virus at this time, and medical treatment focuses on managing symptoms and offering supportive care.

In the past, the number of reported cases of EEEV, which was first recognized in humans in 1938, has been extremely low. According to the Centers for Disease Control and Prevention, the number of reported cases of EEEV annually is fewer than 10. The actual number of EEEV cases may be higher because it’s likely that some cases of the rare disease are undiagnosed or misdiagnosed.

Zika virus, which is linked to severe birth defects in infants whose mothers became infected while pregnant, is still a problem. The only thing that has disappeared are the headlines addressing it.

In the U.S., widespread use of screens, air conditioning and the presence of mosquito control districts have sharply limited the Zika threat. So far in 2019, there have been five confirmed cases of Zika in the U.S., each acquired during international travel. There have been no known cases due to local mosquito-borne transmission.

Limit exposure to mosquitoes with the use of screens, mosquito repellent and by covering bare skin. Remove standing water near your home. Be aware of the times of day the specific mosquitoes in your area are active.

Mosquitoes are frail and fly best in still air. A fan can stir enough breeze to keep them from reaching their target.

Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health. Send your questions to

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