Massachusetts officials say they'll conduct aerial spraying of pesticides in the Southeastern part of the state this week to prevent the spread of Eastern Equine Encephalitis virus (EEE), a rare but potentially fatal virus spread by mosquitoes.

According to the U.S. Centers for Disease Control and Prevention, there were just six cases of EEE in the nation last year. Approximately 30% of people with EEE die and many survivors have ongoing neurologic problems.

Massachusetts hasn't conducted aerial spraying for EEE since 2012, and there hasn't been a human case of the virus in the state since 2013.

"But in 2019 we are finding EEE in mosquitoes that are capable of transmitting the virus to humans," said State Epidemiologist Dr. Catherine Brown of the Department of Public Health. "We are seeing very large populations of those mosquitoes. And we also have weather conditions which are appropriate to support ongoing risk."

Brown said 22 communities in Bristol and Plymouth Counties are considered at high risk right now.

"The aerial spray does not eliminate risk," Brown said. "It is necessary to help reduce risk, but it does not replace or prevent the need for residents to continue to take measures to help protect themselves from mosquito bites."

A full list of the communities and information about the spraying can be foundhere.

For several evenings beginning Thursday, planes are expected to spray a pesticide called Anvil 10+10 across much of the area considered at risk.

"There are no expected health risks associated with the appropriate application of this product," said Brown. State officials aren't recommending any special precautions, but they say residents can reduce their exposure by staying indoors during spraying. The spraying shouldn't affect drinking water, officials said.

"Because the spray breaks down rapidly in both sunlight and water, large water bodies are not expected to be a significant issue," Brown said.

The chemicals can affect bees, however. But John Lebeaux, commissioner of the state Department of Agricultural Resources, said that exposure should be limited because the spraying will be done at night.

"That is the best time to spray for bees, because it's their nature to return to the hives in the evening," Lebeaux said. "And with the very short active life of the product, we think that will greatly reduce any exposure to bees."

Lebeaux said they'll monitor hives in the spray area in the days after the spraying. He said there were no recorded impacts when the state sprayed with the same chemicals in 2012.

"Certainly there's a concern about all our pollinators," Lebeaux said. "I mean, all aspects of agriculture throughout the country are concerned about it. But this is the product that the EPA has registered particularly for aerial sprays."

The chemicals are also known to impact fish, but Lebeaux said spraying at night means fish are less likely to be surface feeding.