BOSTON -- A 58-year-old Everett woman has become the state's second victim of Eastern equine encephalitis and its fifth confirmed case of the mosquito-borne virus, Massachusetts health officials announced Monday.

The Massachusetts Department of Public Health Monday confirmed the fifth human case of Eastern Equine Encephalitis in 2006. The woman fell ill on Sept. 11 and was hospitalized the next day. Her death Sept. 18 was the second EEE fatality of the year. Her family indicated that she traveled to southeastern Massachusetts during the Labor Day holiday and it is possible that she was exposed at that time.

"There is no question that the southeast and northern Essex County along the New Hampshire border are the highest risk areas for EEE, but these individuals EEE cases could occur (anywhere)," said Dr. Al DeMaria, of the Department of Public Health.

DPH also confirmed a case of West Nile virus, the less severe form of the disease. The individual, a 55-year-old woman from Billerica, is a family member of a WNV case identified earlier in the year from Arlington. She reported traveling to visit her family member and their symptoms both began at the end of August. She never required hospitalization and is recovering.

In addition to the Billerica and Arlington cases, there was another human case of West Nile virus in Massachusetts this year, in Webster.

Mosquito control and state public health officials have stepped up their surveillance efforts in these areas and are continuing to monitor the situation closely.

Four other Massachusetts residents have been diagnosed with the mosquito-borne virus this year. A 9-year-old Middleborough boy died in August of the virus. A 23-year-old Rochester man, a 73-year-old Fairhaven man and a 53-year-old Lakeville woman were also hospitalized with EEE this year.

Experts said the risk of humans becoming infected with EEE will continue until the first hard frost. But DeMaria said the risk of becoming infected with WNV can continue even after the first frost.

"Even after a hard frost, with warm weather, West Nile virus can come back again. Back in 2001, we actually had a case in late November -- it was a very warm fall. We need to keep a lookout for West Nile activity," DeMaria said.

Symptoms of EEE infection in humans include high fever, mental confusion, headache, stiff neck and lack of energy. The symptoms usually appear five to seven days after infection.