New York is currently experiencing a significant increase in the number of mosquitoes carrying the lethal Eastern Equine Encephalitis (EEE) virus, prompting state officials to declare an “imminent threat.” This outbreak has already been linked to a rare fatality within the state.
Typically, the state’s monitoring systems detect EEE in mosquitoes across two to three counties annually. However, this year, the virus has been identified in mosquitoes from 15 different counties spread throughout New York, according to State Health Commissioner James McDonald.
“This year, Eastern Equine Encephalitis has taken a more severe turn,” explained McDonald, highlighting the fatal potential of the virus, which has a death rate of 30 to 50 percent. He emphasized, “Mosquitoes have evolved from being a mere annoyance to a significant threat. I strongly advise every New Yorker to take precautions against mosquito bites by utilizing insect repellents, wearing long sleeves, and eliminating standing water around their residences. Although autumn has arrived, mosquitoes will remain a concern until the temperature consistently falls below freezing at night.”
This Monday, McDonald declared a public health emergency due to the imminent threat of EEE, coinciding with Governor Kathy Hochul’s announcement of statewide measures to combat the virus. This announcement was made alongside news of a New York resident’s death from EEE, confirmed on September 20 in Ulster County—the state’s first EEE case since 2015.
EEE is exceptionally rare in New York, with only 12 reported cases from 1971 to 2024, seven of which were fatal.
Infrequent Yet Fatal
In the United States, EEE is generally uncommon, with an average of about 11 cases reported annually, according to the Centers for Disease Control and Prevention (CDC). The virus primarily resides in wild birds and is transmitted to humans and other animals through mosquito bites. It is notably deadly in horses, as suggested by its name, with death rates reaching up to 90 percent. However, most mosquito bites carrying the EEE virus do not result in illness. The CDC estimates that only about 4-5 percent of those infected will develop the disease, with the majority showing no symptoms at all.
For those who do contract EEE, the virus initially spreads via the lymphatic system, leading to a widespread infection. Early symptoms are nondescript and can include fever, headaches, fatigue, chills, joint pain, nausea, and vomiting. The illness may advance to more severe complications such as brain inflammation and neurological issues like confusion and seizures. The disease poses the highest risk to children under 15 and adults over 50.
About 30 percent of those who develop severe forms of EEE succumb to the disease, according to CDC data. However, due to the small number of cases, mortality rates have varied. For instance, in Massachusetts, around 50 percent of EEE cases have been fatal. Survivors of the more severe forms of the disease often suffer significant disabilities, and some die within a few years due to related complications. Currently, there is no vaccine available for EEE, nor are there any specific treatments.
National Overview
Although New York is witnessing a noteworthy increase in EEE-positive mosquitoes, the overall number of cases across the United States has not shown a significant rise. To date, only 10 cases have been reported from six states to the CDC this year. This figure does not include the recent New York case, which would adjust the national total to 11, aligning with the average annual case count.
States reporting EEE cases this year, besides New York, include Massachusetts, Vermont, New Jersey, Rhode Island, Wisconsin, and New Hampshire. The majority of these cases occur in the Northeast, generally between mid-June and early October, before colder weather exterminates the mosquito populations.
The recent fatality in New York is at least the second EEE death reported this year. Earlier in August, New Hampshire health authorities reported an EEE fatality, identified by local media as a previously healthy 41-year-old man from Hampstead.
EEE became a topic of heightened concern last month when a small town in Massachusetts recommended an evening curfew to minimize mosquito exposure after the state confirmed its first EEE case of the year and declared a “critical risk level” in four areas.
The peak of EEE cases in recent years occurred in 2019, with 38 instances reported across various states.
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