2nd case of EEE reported in Massachusetts, bringing total in US to 6

Health officials in Massachusetts have confirmed a second case of Eastern Equine Encephalitis (EEE) in a person.

The patient is a woman in her 30s who was exposed in the area of Plymouth County, in the southeastern part of the state, according to an update published Thursday by the Massachusetts Department of Public Health (MDPH).

The MDPH said the woman was in an area that had been aerially sprayed for mosquitoes on Tuesday night, and she became infected before spraying was done this week.

A horse in the area also tested positive for EEE, the second confirmed case in a horse this year, the MDPH said.

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The cases come after 10 communities in Massachusetts, including Plymouth, were designated as being under high or critical risk of the virus earlier this week, according to the MDPH. Many of the affected areas began implementing targeted mosquito spraying to protect residents, officials said.

"This evidence of the spread of EEE to a person and a horse in Plymouth County before aerial spraying confirms risk in the area," Dr. Robbie Goldstein, MDPH public health commissioner, said in a statement on Tuesday. "We expect that the aerial spraying will help prevent risk for EEE from continuing to escalate in the area, but it does not eliminate it completely. We are asking people to be consistent about taking steps to prevent mosquito bites."

The Massachusetts case is likely at least the sixth case of EEE so far this year, according to an ABC News tally. This also includes the four known cases listed on the Centers for Disease Control and Prevention (CDC) website, as well as a patient in New Hampshire, who may have died of the disease.

Most people who are infected with EEE show either mild symptoms or no symptoms at all, according to the CDC. However, severe cases usually present with fever, headache, chills and vomiting before progressing to the more serious encephalitis, which is inflammation of the brain, or meningitis, which is inflammation of the membranes that surround the brain and spinal cord.

About a third of all people who develop severe EEE die from the illness, the CDC says, while survivors can experience ongoing physical and neurological problems, including seizures, paralysis, cranial nerve dysfunction, personality disorders, and intellectual disabilities that can range from mild to severe.

There are no human vaccines or treatments specifically to address EEE. The CDC says rest, fluids, and over-the-counter pain medications may help relieve some symptoms.

ABC News' Youri Benadjaoud contributed to this report.