Following the season's first positive test for Eastern equine encephalitis in a mosquito, state officials are continuing studies in an attempt to gauge the summer outlook for the spread of the potentially fatal virus.

Following the season's first positive test for Eastern equine encephalitis in a mosquito, state officials are continuing studies in an attempt to gauge the summer outlook for the spread of the potentially fatal virus.

The state Department of Public Health and the Bristol County Mosquito Control Program should have the results from the latest round of testing later this week.

“By Friday, or maybe as soon as Wednesday, we’ll know a lot more,” program director Wayne Andrews said.

A Raynham mosquito collected July 4 was the first in the state this year to test positive for the potentially fatal EEE, which can be passed to humans through the bite of an infected mosquito.

Since last week’s positive test result, the Bristol County Mosquito Control Program has stepped up its truck-mounted pesticide spraying.

“We’ve been spraying around the Hockomock Swamp, down around New Bedford and in recreational areas, like playgrounds,” Andrews said.

The Department of Public Health has also increased its mosquito surveillance and trapping after the recent positive test.

“We also are contacting hospitals and healthcare facilities in case someone comes in with the symptoms and they weren’t thinking of EEE,” said Dr. Alfred DeMaria, director of the department’s communicable diseases division.

EEE can produce symptoms ranging from high fever and stiff neck to swelling of the brain. It is fatal in 30 to 50 percent of human cases, with children and the elderly being at the highest risk.

The next round of test results could help health officials predict EEE infection rates for the rest of the summer.

The presence of EEE, Andrews explained, has historically gone through three-or-four-year peak periods.

Since the mosquito-borne virus has been present at high levels for the past three years, officials are waiting to see if this is the end or a continuation of the current cycle.

“We’re all eager to see the results,” Andrews said.

Last year was one of the worst on record for EEE.

In 2006, 144 mosquito pools tested positive for the virus. To put that number in perspective, there were 45 positive tests for EEE in 2005, which was also considered a bad year for the disease.

Due to recent weather conditions, the mosquito population seems to be dropping, unlike last year, Andrews said.

There have been 87 documented cases of EEE in humans in Massachusetts since 1938.

Since 2005, all eight human cases of EEE in the Commonwealth have been in Plymouth and Bristol counties.

Last year, 9-year-old Johnny Fontaine of Middleboro died after being infected with the virus. A Lakeville woman and a man from Acushnet survived being bitten by infected mosquitoes.

Statewide 158, or 0.08 percent, of the 185,245 mosquitoes tested in 2006 were infected with EEE.

But the rate of infection is higher in Southeastern Massachusetts, where swampy terrain has made the region the epicenter of the state’s EEE scare in recent years. In Raynham, 0.15 percent of mosquitoes tested had EEE. In Lakeville it was 0.19 percent.

The infection rate for mosquitoes in Freetown was 0.42 percent.

If the tests show that this summer is shaping up to be like last year, state Sen. Marc R. Pacheco, D-Taunton, said he will ask the Department of Public Health to conduct aerial pesticide spraying.

The state’s airplane-mounted spraying last year was the first since 1990, when there were three human cases of EEE.

“I’ve always advocated for aerial spraying when it’s an appropriate time to do it,” Pacheco said.

He noted that spraying does not eliminate the risk, but does greatly reduce it. People must still use caution and common sense while working or playing outdoors, he said.
DeMaria said the Department of Public Health will consider aerial spraying again this year if infection rates warrant it.

Health officials are also on the look out for West Nile Virus, which is also carried by mosquitoes and is characterized by symptoms similar to EEE.

Since 2001, when the virus first appeared in Massachusetts, it has infected 55 people. West Nile Virus peaked in 2002, when there were 25 human cases.

Health officials recommend reducing the risk of EEE and West Nile Virus by avoiding mosquitoes as much as possible.

Using insect repellent with DEET, eliminating pools of standing water and limiting outdoor activity at dawn and dusk are the best ways to reduce the risk of mosquito bites.

Gerry Tuoti of The Taunton (Mass.) Daily Gazette may be reached at gtuoti@tauntongazette.com.