A lot of health and school officials are no doubt breathing a sigh of relief this week now that NOAA’s National Weather Service and local Massachusetts health boards confirmed that last weekend’s frost was hard enough to dramatically ease the threat of mosquitoes and mosquito-borne illnesses.
But in some Southern New Hampshire communities, authorities say there is still cause for concern.
It all has to do with temperature. How cold was it and for how long? That’s what determines if enough mosquitoes survived to pose a continued threat of West Nile Virus or eastern equine encephalitis — better known as EEE.
In Haverhill, sports returned under the lights of Trinity Stadium and Riverside Park after the city lifted a ban on outdoor sports after dusk that was instituted last month. Last week, Haverhill High School held its first varsity and junior varsity field hockey games at Trinity Stadium since the since the ban began.
Mayor James Fiorentini ordered the ban to be lifted at the recommendation of Board of Health Chairman Dr. Carl Rosenbloom. Below-freezing temperatures over the weekend and a killing frost reduced the threat of mosquito-borne illnesses. Officials had previously announced the ban would be in effect until the first hard frost.
The National Weather Service defines a hard freeze as temperatures dropping below 28 degrees at any time or at least below 32 degrees for three hours or longer. That was the case in the early morning hours of Saturday, Oct. 13, when the NWS said most of Southern New England had a hard freeze.
But in parts of Southern New Hampshire, the temperature did not get cold enough. The temperature dropped to 30 degrees, just slightly below freezing.
“I was hoping it was 25 degrees,” Sarah MacGregor, owner of Dragon Mosquito Control, told reporter Doug Ireland. “It wasn’t cold enough for long enough.”
And so early last week, a batch of mosquitoes from Stratham tested positive for West Nile — a strong indication the public must still protect themselves from mosquitoes, according to Beth Daly, chief of infectious disease surveillance with the New Hampshire Department of Health and Human Services.
“We still think there is a risk out there,” Daly told Ireland. “People should continue to take precautions.”
While mosquito populations surely have been reduced by the cold weather, it is still worthwhile to take sensible precautions. With cooler temperatures, most people are likely wearing long sleeves and pants anyway.
Enjoy the fall weather and outdoor activities. At local high schools, it’s time for “Friday night lights” on the gridiron. At home, there is time for maybe one or two more cookouts before the snow flies.
Enjoy it all while it lasts.