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Officials confirmed two more human cases of EEE Friday, including a 5-year-old Sudbury girl and a Northborough woman in her 60s — and one state scientist said she expects more cases in coming weeks.

According to Sudbury town officials, the child is in critical condition at an area hospital. All outdoor evening town and school activities in Sudbury were cancelled Friday. Outdoor events for Lincoln-Sudbury Regional High School were also cancelled.

Northborough’s health agent confirmed in a Friday statement that the other new case of EEE was a town resident.

The new cases announced Friday brought the state’s tally to seven and caused risk levels to be raised in a number of Massachusetts communities. In Framingham, Marlborough, Northborough, and Sudbury, the risk levels were raised to critical, while the levels in Berlin, Boylston, Hudson, Maynard, Stow, and Wayland have been raised to high.

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Critical risk prompts the state to encourage outdoor gatherings like organized sports events be cancelled or rescheduled to avoid the peak mosquito hours from dusk until dawn. High risk means “conditions likely to lead to infection of a person with EEE occurring in your area.”

EEE is a rare but potentially fatal disease that can cause brain inflammation and is transmitted to humans bitten by infected mosquitoes, according to federal authorities. Those who recover from it often live with severe and devastating neurological complications. There is no treatment.

Earlier this year, a Fairhaven woman with EEE died.

Although local mosquito populations are beginning to decrease because of the cooler temperatures, EEE risk in the state will continue until not just the first frost, but the first “hard frost,” said Dr. Catherine Brown, an epidemiologist for the state.

Speaking at a Friday afternoon press conference in downtown Boston, Brown said more human cases of EEE in Massachusetts are likely this year, including possible deaths, but she stopped short of calling the current rash of illnesses a public health crisis.

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“It is certainly something that we are paying a lot of attention to,” she said.

She said historically most people who get the disease in Massachusetts become sick before Sept. 15, when temperatures typically begin falling.

The state, said Brown, is approaching the “end of the traditional peak transmission period.”

Still, the state’s public health commissioner, Dr. Monica Bharel, said in a statement confirming the two most recent cases that it is “not unusual to see human EEE cases confirmed in September.”

“This is why we continue to urge the public to take seriously the threat that mosquitoes can pose and to take steps to avoid being bitten,” she said in the statement.

EEE cycles are “partially triggered when a new variant of the virus” is introduced to the state by migratory birds from the southeastern part of the country, she said.

“We think that is probably what happened this year,” she said.

About one-third of infected individuals who develop the disease die, according to federal officials.

And, Brown said, survivors can have “very high levels of permanent neurological impairment.”

Symptoms can include high fever and headaches, but because the virus invades the central nervous system, patients can also have “rapid progression in changes of level of consciousness and seizures,” said Brown.

On Thursday, officials announced that the state’s fifth human case of EEE this year had been confirmed in a man in his 70s from southwestern Middlesex County.

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That case prompted officials to raise risk levels for EEE in Ashland, Hopedale, and Milford to critical and the risk levels in Bellingham, Blackstone, and Millville to high.

All told, 36 communities are now at critical risk, 42 at high risk, and 115 at moderate risk for the EEE virus in Massachusetts, according to state officials.

Also, nine cases of EEE have been confirmed this year in animals: eight horses and one goat.

The MSPCA is expanding its emergency EEE vaccination services for horses whose owners cannot afford the vaccination to Southern New Hampshire, Bristol County, and south central Massachusetts, the group announced Friday.

The emergency clinic was originally serving only the Merrimack Valley — where one horse died in Methuen — but the MSPCA chose to expand it because of the high demand from horse owners in Southern and Western Massachusetts, as well as Southern New Hampshire, said Rob Halpin, a spokesman for the Massachusetts Society for the Prevention of Cruelty to Animals.

Local communities are continuing truck-mounted spraying for mosquitoes, authorities said.

The state completed aerial mosquito spraying in parts of Bristol, Plymouth, Middlesex, and Worcester counties in August. Sudbury will have townwide spraying on Monday and Tuesday, weather permitting.

The EEE virus has also been detected on the Outer Cape, with mosquitoes carrying the potentially deadly disease found in Wellfleet, according to town officials.

In a statement dated Wednesday, officials in the popular summer tourist town said the “Massachusetts Department of Public Health (MDPH) announced today that EEE virus has been detected in mosquitoes collected from Wellfleet. The samples were taken on August 29, 2019, and we continue to sample the area.”

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Globe correspondent Maria Lovato contributed to this report. Danny McDonald can be reached at daniel.mcdonald@globe.com. Follow him on Twitter @Danny__McDonald. Travis Andersen can be reached attravis.andersen@globe.com. Follow him on Twitter @TAGlobe.