Bristol County Man First EEE Human Victim In Mass.

An elderly man from Bristol County has become the first person infected this year with Eastern Equine Encephalitis, a rare and potentially fatal brain infection spread by mosquitoes.

Mosquito populations are thriving following Tropical Storm Irene, according to Dr. Alfred DeMaria, a doctor with the Massachusetts Department of Public Health. Officials are urging residents to take caution.

"We monitor it very closely in the hopes that there won't be human cases," DeMaria said. "Unfortunately, this is one. As far as we know, he is not doing very well."

The public health department says testing at the Hinton State Laboratory Institute confirmed the infection on Friday. The patient became ill on Saturday and was hospitalized Monday.

There was one human case of EEE in the state in 2010, together with a Rhode Island resident who was probably exposed to the virus in Massachusetts.

Officials say several mosquito pools have tested positive for the virus in several towns in Bristol and Plymouth counties this year.

The Centers for Disease Control says an average of five human cases of the disease occur each year in the U.S.

The Associated Press contributed to this report.