Mosquito boom follows wet spring
Spikes in West Nile virus and Eastern equine encephalitis could result
A wetter-than-normal spring in the Northeast is producing a bumper crop of mosquitoes, leading to worries of a corresponding spike in mosquito-borne illnesses this summer.
The heavy rain that erased last summer’s drought has put public health officials on alert as summer begins to unfold.
“Anecdotally, everybody is telling me that they’re being eaten alive by mosquitoes,” said Sara Robinson, an epidemiologist for the Maine Center for Disease Control.
But, she hastened to add, it’s too early to say whether there will be an increase in West Nile virus and Eastern equine encephalitis.
The rain has created ideal conditions for mosquitoes, though. It was the fourth-wettest spring on record in the Northeast, said Samantha Borisoff, from the Northeast Regional Climate Center at Cornell University.
It was rainier than usual in many other parts of the country,
too, so many areas are registering some of the same concerns.
The rainfall saturated the ground in Maine, creating standing water required for mosquitoes to breed, said Chuck Lubelczyk, of the Maine Medical Center Research Institute. Mosquitoes have been especially bad on Maine’s coast, he said.
Several other factors would have to come together to create a scenario in which mosquito-borne illnesses become a big problem.
There has to be a concentration of the right mosquito species along with the presence of the virus, said Janet McAllister, from the Center for Disease Control and Prevention’s Division of Vector-Borne Diseases.
All told, each U.S. state has about 50 or 60 species of mosquitoes, and only a dozen are considered to be major vectors for diseases that threaten humans, McAllister said. West Nile can produce a fever, head and body aches, skin rash and swollen lymph nodes, though sometimes people show no symptoms. Eastern equine encephalitis is rarer but much more dangerous, potentially causing brain damage or death.
Zika virus, which can be passed from pregnant mother to fetus and cause birth defects, is another concern, but it’s never been transmitted by mosquitoes in the U.S. outside of Florida.
New England is in a waiting period. Human cases of Eastern equine encephalitis and West Nile tend to appear in mid- to late summer, if they appear at all.
But the viruses are around elsewhere this summer. West Nile cases in humans have been reported in 11 states, and Eastern equine encephalitis has been detected in mosquitoes in Texas, Mississippi and Florida, McAllister said.
There also have been 143 Zika cases in the U.S., all associated with travel outside of the country, she said.