FRAMINGHAM — Aerial spraying begins Monday in certain sections of Framingham to control mosquito populations that could carry the potentially deadly Eastern Equine Encephalitis virus. In a press release, city officials said the East Middlesex Mosquito Control Project will use a helicopter to drop small particles of a relatively non-toxic pesticide known as Bti. It's scientific name is Bacillus thuringiensis subspecies israelensis. Bti will be dropped over wetlands in the vicinity of Angelica Drive, Callahan State Park, Fairbanks Road, Palmer Road and Walnut Street. Spraying continues through April 30, between dusk and 11:30 p.m. Statewide, there were 12 human cases of EEE — including six deaths — in 2019, the most intense outbreak in Massachusetts history.