BOSTON -- The state is preparing to take steps to fight back against the growing health threat posed by the eastern equine encephalitis virus, which officials said is now at unprecedented levels in Southeastern Massachusetts.

Describing the situation as a "major public health concern," Gov. Deval Patrick announced Tuesday that the state will launch a two-pronged ground and air attack in Plymouth and Bristol counties to combat the mosquitoes that carry the virus.

After dark Wednesday, he said, the state will spray 12 counties entirely and 15 counties partially. ( List of Towns To Be Sprayed )

He said the EEE virus is being found in Massachusetts at levels not seen before and that has raise concerns about the potential for human infection.

Video

Aerial spraying has been approved by Gov. Deval Patrick and the Department of Health and it could begin as early as Wednesday night. The exact times and locations have not yet been announced.

The unprecedented levels of EEE are being attributed to persistent hot weather and rainfall this summer, according to the state health commissioner.

Health officials said samples from 30 pools have tested positive for EEE and that figure is more than triple what state researchers typically find.

Also, the mosquitoes are considered "hot," which indicates that they're carrying very potent levels of the virus.

While there haven't been any human cases of EEE since 2008, between 2004 and 2006, there were 13 cases, including six deaths.

To prevent infection, experts recommend staying indoors between dusk and dawn. For residents who have to go out during those times, they recommend wearing pants and long sleeves and using insect repellent.

They also said if residents have buckets or pails around the house, they're advised against leaving them right side up, because if they collect water and that can be a perfect breeding ground for mosquitoes, which could very likely be carrying the virus.