Why are mosquitoes shutting down towns in Massachusetts? The area is experiencing an outbreak of EEE, or Eastern equine encephalitis. This mosquito-borne virus causes flu-like symptoms in 95% of cases, and dangerous brain inflammation in the remaining 5%. This brain inflammation can be fatal in 30% of cases, so health officials are taking serious precautions such as encouraging people to stay indoors from dusk to dawn, when mosquitoes are most active. This outbreak can be tied to climate change because warmer weather means longer mosquito seasons!