The virus is spread by adult mosquitoes, which are killed by frost in the fall. These symptoms show up two to ten days after infection. Swelling of the brain, called encephalitis, is the most dangerous symptom. The disease gets worse quickly and many patients go into a coma within a week. There is no cure for EE, and three of every ten people who get the disease die from it.
All doctors can do is lower the fever and ease the pressure on the brain and spinal cord.
EE is spread only by mosquitoes. People and horses that have EE cannot spread the disease. EE is so rare that fewer than 80 people in this state have had it since we began counting in 1938. Fewer than 40 cases have occurred since 1940. Most cases have been in Plymouth and Norfolk counties, with a few in Middlesex, Bristol, Suffolk, Barnstable and Essex counties.