Mosquitoes trapped late last week in Andover tested negative for Eastern Equine Encephalitis, or EEE, according to town officials.
Health Director Thomas Carbone said the test result does not mean that the virus is gone, just that there was no trapping of any mosquitoes infected with EEE. He said the trap is tested weekly, and will continue until the trapping process is stopped across the region.
The statement said the town's risk for EEE remains "high." Carbone said the risk level will remain there until the first killing frost of the season, different from a little lawn frost, where mosquitoes can shelter under leaves for survival.
Officials also said multiple tests will need to be negative before the risk level can be moved down.
Twice last month, batches of mosquitoes tested positive for EEE in Andover. Since then, the town has conducted spraying at night, and continuously urged residents to take precautions to avoid bites.
Town officials and the Massachusetts Department of Public Health are urging residents to continue to limit outdoor activities at night beginning at sundown.
According to the statement, outdoor events should end by 7:15 p.m. That time will move earlier as the days shorten in the coming weeks, and will be in effect until the first hard frost. Residents should be aware of peak mosquito hours from dusk to dawn, wear pants and long-sleeve shirts, and use bug spray to avoid mosquito bites.
"We need to assume EEE is in the community, despite the negative tests, and despite the recent spraying by the mosquito control district," Carbone said.