MIAMI (CBSMiami/CNN)  — There is a new warning in Florida about the Eastern equine encephalitis virus (EEEV), a mosquito-borne virus that causes brain swelling in humans. Florida health officials say there is an uptick in the number of cases.

Several sentinel chickens tested positive for EEE, which can spread to humans via infected mosquitoes and cause brain infection and swelling, the Florida Department of Health in Orange County said in a Thursday statement.

Sentinel chickens are fowl that are tested regularly for the West Nile virus and EEE. Their blood can show the presence of the diseases, but they don’t suffer from the effects of the viruses.

Following the positive tests for the sentinel chickens in Orange County, the health department said “the risk of transmission to humans has increased.”

Only about seven cases of the EEE virus in humans are reported in the US each year, the Centers for Disease Control and Prevention says.

However, the disease can be fatal: about 30% of people who contract it die, according to the CDC. Many survivors have ongoing neurologic problems.

FAST FACTS: Encephalitis And Prevention Tips

People develop symptoms about 4 to 10 days after they are bitten by an infected mosquito, the CDC says. Signs include sudden onset of headache, high fever, chills and vomiting. More severe symptoms include disorientation, seizures and coma.

With summer in full swing, mosquitoes are buzzing around at peak populations. Officials warned people to avoid being bitten by draining standing water around their homes, covering skin with clothing or repellent, and using screens to cover doors and windows.

(©2019 CBS Broadcasting Inc. All Rights Reserved. Cable News Network, Inc., a Time Warner Company, contributed to this report.)

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