By Stephanie Stahl

PHILADELPHIA (CBS) — The death toll for mosquito-borne illness Eastern Equine Encephalitis (EEE) has increased. Some communities that are especially hard hit are taking extra precautions.

In our area, New Jersey has had the highest number of cases in both people and horses. It’s unclear why there’s been a spike of EEE this year, and officials also don’t know why certain areas are being harder hit.

Connecticut is being especially hard hit.

“We’ve never had an outbreak as large as the one we’ve had this year. This is the largest outbreak on record,” said Dr. Phil Armstrong, with the Connecticut Mosquito Surveillance Program.

This week, officials in Connecticut and Michigan announced two more deaths from EEE infections, bringing the total number of deaths nationwide to 11. According to the CDC, that includes New Jersey.

In a typical year, there are five to 10 cases, with only a third resulting in death. This year, at least 31 cases have been reported.

The mosquito-borne illness can cause inflammation of the brain.

“Half of the survivors will suffer from permanent neurological damage,” Armstrong said.

The unusual uptick has compelled some communities to start spraying pesticides and increase warnings to residents to stay inside at dawn and dusk.

It’s also impacting sporting events.

“Currently, a lot of the football, volleyball and things like that are getting moved up, especially if they’re outside and even canceled entirely because of the risk,” high school sophomore Benjamin Vae said.

Experts say Mother Nature will help remedy the situation.

“With the onset of cool temperatures, the number of mosquitoes are dropping and declining quite precipitously,” Armstrong said.

But the risk of contracting EEE remains until the first hard frost of the season.

Officials say in spite of the increased number of cases, the illness that’s carried by birds but spread by mosquito bites, is still very rare.

Stephanie Stahl