BOSTON (AP) -- State health officials now say they plan to conduct aerial spraying for mosquitoes in 21 southeastern Massachusetts communities.

The spraying will take place on Friday and Saturday nights after dark. The state is hoping to reduce the threat of Eastern Equine Encephalitis, a potentially deadly disease for humans.

The Department of Public Health on Wednesday added 10 cities and towns to the aerial spraying list, adding to the 11 others previously announced.

State Public Health Commissioner John Auerbach says recent confirmed samples of EEE in mammal-biting mosquitoes in the region have come earlier this year than in the past, something he considers "particularly concerning."

Experts say the mild winter and recent high temperatures may have caused faster breeding and early development of the virus in mosquitoes.