Epi Week #38 - 2017 General Statements

There have been 286 WNV-positive mosquito pools found in 90 cities/towns so far this season, with WNV activity in every mainland county in the state. This has led to the placement of 155 municipalities in 11 counties at MODERATE risk for WNV, more than 40% of the state. In addition, we continue to see high levels of Culiseta melanurain the collections. While the EEEv risk for this season remains extremely low, with only 1 positive pool so far, more Cs.melanura now suggests we will start out next season with increased levels of this species, since the larvae overwinter. That creates the potential for more EEEv activity next season, especially if the jump in population coincides with peak Coquillettidia perturbans levels (the “bridge vector” mosquito that bites both birds and humans).

While mosquito activity has been declining, unseasonably warm weather continues to prolong WNV risk. A shift to more fall-like temperatures in Epi Week 39 should ramp down mosquito activity.

Weather

Epi Week 38 shows clear impacts of the remnants of Hurricane Jose, with the southeastern portion of the state and especially the islands seeing the most rain

At the time this report goes to press, a cold front has come through, finally bringing fall-like temperatures to Massachusetts. Rain is expected at the end of Epi Week 39, followed by a slow creep back up to summer-like daytime temperatures for the central portion of the state. However, nights are expected to remain in the 40s and 50s. Outlook