Eastern Equine Encephalitis, like many diseases, is not a good one to have. According to the Centers for Disease Control and Prevention:
EEE virus is a rare cause of brain infections (encephalitis). Only a few cases are reported in the United States each year. Most occur in eastern or Gulf Coast states. Approximately 30% of people with EEE die and many survivors have ongoing neurologic problems.
The good news above is that this mosquito-transmitted disease is rare. And, CDC gives more good news, especially for people who do not live in swampy areas:
…Human EEEV cases occur relatively infrequently, largely because the primary transmission cycle takes place in and around swampy areas where human populations tend to be limited. All residents of and visitors to areas where EEEV activity has been identified are at risk of infection. People who engage in outdoor work and recreational activities in endemic areas are at increased risk of infection. Persons over age 50 and under age 15 seem to be at greatest risk for developing severe disease when infected with EEEV. Overall, only about 4-5% of human EEEV infections result in EEE. EEEV infection is thought to confer life-long immunity against re-infection.
So, as with West Nile Virus, only a fraction of infected humans have serious symptoms and it seems probable that even a low-grade and often unnoticeable infection confers subsequent immunity.
To put those figures in perspective, Chester County alone had 118 reported opioid overdose deaths in 2018.