The Hippo


May 19, 2019








Pest peeves
State hit by historic West Nile Virus numbers


 By Scott Murphy 
Twenty-nine mosquito batches found in southern New Hampshire have tested positive for West Nile virus since the beginning of July — the most in five years. 
As a result, Gov. Chris Sununu and the New Hampshire Department of Health and Human Services issued a public health threat declaration on Sept. 13, covering 29 cities and towns in southern New Hampshire. 
In Manchester, the risk level for human illness has been elevated to “high.” Nine of these 16 batches were found in the Queen City. 
“When we saw sustained activity at sites around the city, that bumped us pretty quickly from low to moderate to high,” said Philip Alexakos, chief of environmental health and emergency preparedness at the Manchester Health Department. “We collected our first positive batch [for West Nile virus] on July 16, which was the earliest we had detected a positive batch by about three days.”
West Nile was first identified in New Hampshire in 2000. The virus causes one of three mosquito-borne illnesses found in the state, along with Eastern Equine Encephalitis (or Triple E) and the Jamestown Canyon virus. The New Hampshire Department of Health and Human Service announced Monday that it tested two mosquito batches in Newton and Sandown that tested positive for EEE. 
Abigail Mathewson, surveillance epidemiology program manager at the New Hampshire Bureau of Infectious Disease Control, said the main concern is “bridge vectors,” or species of mosquitoes that feed on both birds and mammals and can therefore pass West Nile (found in infected birds) to humans. People bitten by a mosquito infected with West Nile will likely notice flu-like symptoms within a week, including fever, muscle aches, headaches and fatigue. A very small percentage of individuals infected can go on to develop more serious central nervous system disease, including meningitis or encephalitis.
Though EEE has similar signs and symptoms to West Nile Virus, EEE can be a more severe disease and has a high mortality rate for those who develop encephalitis.
Severe season
Weather has been the main driver of this season’s buzzing activity. The Granite State has experienced “perfect mosquito weather,” according to Mathewson, specifically a combination of consistent heat and heavy rain. While mosquitoes in general thrive in hotter weather, this summer’s pattern of precipitation followed by sweltering heat has been particularly kind to mosquitoes that commonly carry West Nile.
“One of the differences between West Nile virus and Triple E is that West Nile tends to be found in what we would consider ‘container breeding mosquitoes,’” said Mathewson. “People aren’t paying attention to what they have in their yard. Anything that can pool water can be a breeding habitat for mosquitoes.”
That includes everything from flower pots to kiddie pools to wheelbarrows, which have had plenty of opportunities to fill up with rainwater this summer. Mathewson said it’s important for people to be mindful of these kinds of pools that might be forming on their properties and try to dump them out after heavy rainfall.
Though summer is in the rearview at this point, the risk of infection is still a point of concern. Mathewson said this is partially due to the perception that mosquito season is over, which leads more people to stop applying bug spray as frequently, if at all. 
Meanwhile, Mathewson said mosquitoes will continue taking blood meals and laying eggs until the first hard frost kills them off. This can lead to more mosquitoes with more options for people to bite, as well as more time to potentially become infected with West Nile. 
“This is the time of year to be very aware of vectors and vector-borne diseases,” said  Mathewson. “People should be mindful of that throughout the rest of the season until we have our first hard frost. Until then, the risk will continue to increase.”
Squash out risk
Alexakos and Mathewson both said prevention is key. They recommended applying DEET or another form of bug repellant, particularly when going through particularly forested areas. 
Along with emptying out receptacles for rainwater, Mathewson also recommended homeowners keep their grass short and ensure there’s at least a 3-foot boundary between their property and wooded habitats that mosquitoes might call home. Homeowners could also get rid of bird feeders to eliminate the risk of mosquitoes contracting West Nile from an infected bird that stops by.
“Prevention is a 24/7 job,” said Alexakos. “We want folks to realize that just because we have a positive batch ‘here’ and not ‘there’ doesn’t mean people shouldn’t use the same precautions.”
For more information from the Bureau of Infectious Disease Control, visit 

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