What is EEE? 4 US Towns Under Curfew Over Virus Concerns

EEE is a life-threatening viral disease carried by mosquitoes. Source

When Americans experience viral outbreaks, they often do so through the news, watching strangely named diseases rage in distant countries. But today, ground zero for a rare and deadly virus is much closer to home. The last few days have seen the towns of Douglas, Oxford, Sutton, and Webster in Massachusetts confront a serious public health threat: Eastern equine encephalitis (EEE).

This alarming development came after the Massachusetts Department of Public Health confirmed the first human case of the deadly EEE virus in the region since 2020. Only two other states, Vermont and New Jersey, have had human EEE cases this year. Due to the virus’s high mortality and presence in mosquitoes, local authorities have recommended a curfew in response. Residents are advised to remain indoors after 6:00 p.m. through September 30, and starting even earlier, at 5:00 p.m., from October 1 until the first frost. Using insect repellent and avoiding nonessential activities is also recommended.

The curfews are a direct response to the behavior of the mosquitoes that carry the EEE virus. These mosquitoes are most active from dusk to dawn, which is why residents in the affected towns are being urged to stay indoors during these hours. By reducing outdoor activity during peak mosquito times, the risk of exposure to the virus is significantly lowered. However, the risk is never zero and it’s still up to residents to decide how strictly they want to adhere to the curfew.

What is EEE?

Eastern equine encephalitis is a rare but severe viral infection transmitted to humans through the bite of an infected mosquito. Though its name might suggest it primarily affects horses, EEE can be deadly for humans. About 96% of those infected never experience symptoms, but those who do fall ill with the disease are in for a harrowing experience. After an incubation period of 3-10 days, victims develop fever, headaches, muscle aches, nausea and vomiting. Brain inflammation follows, and about 30% of those who fall ill die. Even those who survive tend to suffer severe symptoms and long-term consequences.

The EEE virus is found across the Americas and carried by the Culiseta melanura mosquitoes. It's most at home in wetlands where mosquitoes pass the virus onto susceptible birds. Cases are most known to occur along the eastern coast of the United States, which is home to the group 1 lineage of the EEE virus. Sporadic human cases occur annually, as do occasional serious outbreaks in horses.

Since it was first discovered in Massachusetts in 1933, EEE has only caused 115 cases in the state. Outbreaks are rare and typically occur every 10-20 years, though only four have passed since the state’s last major outbreak. In the context of other rapidly emerging arboviruses (viruses spread by mosquitoes, ticks, and other arthropods) like West Nile and Zika, the threat posed by EEE is a serious one. Where EEE is headed and whether it will grow into a much larger threat like other arboviruses is uncertain, but there is cause for concern. 2019 saw one of the largest outbreaks in US history and conditions that broaden the range of carrier mosquitoes could be affected by climate change.

EEE cases in the United States by year. Source: CDC

At a time when global travel and climate change are contributing to the spread of new and emerging viruses, the importance of public health preparedness cannot be overstated. While EEE may not be as dramatic as a global pandemic, the sudden curfews in New England towns show how quickly disease can strike.