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 as Americans grill and play outdoors.

The heavy rain that has erased last summer’s drought has put public health officials on alert as summer begins to unfold.

Mosquitoes collected by Chris Horton of the Berkshire County Mosquito Control Project are displayed in Pittsfield, Mass. Ben Garver/The Berkshire Eagle via Associated Press

“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 and Prevention.

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 pesky mosquitoes, though. It was the fourth-wettest spring on record in the Northeast and the wettest April ever recorded in Buffalo, New York, said Samantha Borisoff from the Northeast Regional Climate Center at Cornell University.

It was rainier than usual in many other parts of the country, 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.

While the rain is a concern, several other factors 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, and most mosquito species are not a threat to humans, 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, she said.

West Nile can produce a fever, head and body aches, skin rash and swollen lymph nodes, though sometimes people show no symptoms. EEE is rarer but much more dangerous, potentially causing brain damage or death.

The Zika virus, which is associated with 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 EEE 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 EEE has been detected in mosquitoes in Texas, Mississippi and Florida, McAllister said. There have been 143 Zika cases, all associated with travel outside the U.S., she said.