No town and school events will be held from dusk to dawn, due to the threat of mosquitoes infected with the Eastern equine encephalitis virus. The activity ban will be in effect until the first frost, officials said. “We are in a high alert status from the Massachusetts Department of Public Health,” said Michael Gallagher, Weymouth’s director of administrative services. The state reported that an 85-year-old Weymouth woman died from EEE last month, the first Massachusetts fatality this year from the mosquito-borne virus. The activity ban includes school sports and outdoor movies sponsored by the town.