Statistics & Maps
Eastern equine encephalitis virus (EEEV) is transmitted to humans through the bite of an infected mosquito. 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. It does not confer significant cross-immunity against other alphaviruses (e.g., western equine encephalitis virus), and it confers no cross-immunity against flaviviruses (e.g., West Nile virus) or bunyaviruses (e.g., La Crosse virus).
In the United States, an average of 11 human cases of EEE are reported annually. To ensure standardization of reporting across the country, CDC recommends that the national surveillance case definition be consistently applied by all state health departments.
From 2012-2021, most cases of EEE have been reported from Massachusetts, Michigan, Florida, Georgia, and North Carolina. EEEV transmission is most common in and around freshwater hardwood swamps in the Atlantic and Gulf Coast states and the Great Lakes region.
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
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Year | Number of Reported Cases |
---|---|
2012 | 15 |
2013 | 8 |
2014 | 8 |
2015 | 6 |
2016 | 7 |
2017 | 5 |
2018 | 6 |
2019 | 38 |
2020 | 13 |
2021 | 5 |
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
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State | Number of Reported Cases |
---|---|
Alabama | 2 |
Arkansas | 1 |
Connecticut | 5 |
Florida | 9 |
Georgia | 9 |
Indiana | 2 |
Louisiana | 1 |
Maine | 2 |
Maryland | 1 |
Massachusetts | 25 |
Michigan | 19 |
Montana | 1 |
New Hampshire | 3 |
New Jersey | 5 |
New York | 5 |
North Carolina | 8 |
Pennsylvania | 1 |
Rhode Island | 3 |
South Carolina | 1 |
Tennessee | 1 |
Vermont | 2 |
Virginia | 1 |
Wisconsin | 4 |
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
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Data Table: This map shows the distribution of eastern equine encephalitis virus neuroinvasive disease average annual incidence by county of residence from 2012 through 2021. Counties are shaded according to incidences ranging from less than 0.20, 0.20 to 0.49, and greater than 0.50 per 100,000 population. Shaded counties are primarily distributed along the Gulf Coast, Eastern Seaboard, and the Great Lakes.
Additional Maps, Charts, and Tables
Eastern equine encephalitis virus disease cases and deaths reported to CDC by year and clinical presentation, 2012-2021
Neuroinvasive disease | Non-neuroinvasive disease | Total | ||||
---|---|---|---|---|---|---|
Year | Cases No. |
Deaths No. (%) |
Cases No. |
Deaths No. (%) |
Cases No. |
Deaths No. (%) |
2012 | 15 | 5 (33) | 0 | 0 (0) | 15 | 5 (33) |
2013 | 8 | 4 (50) | 0 | 0 (0) | 8 | 4 (50) |
2014 | 8 | 2 (25) | 0 | 0 (0) | 8 | 2 (25) |
2015 | 6 | 4 (67) | 0 | 0 (0) | 6 | 4 (67) |
2016 | 7 | 3 (43) | 0 | 0 (0) | 7 | 3 (43) |
2017 | 5 | 2 (40) | 0 | 0 (0) | 5 | 2 (40) |
2018 | 6 | 1 (17) | 0 | 0 (0) | 6 | 1 (17) |
2019 | 38 | 19 (50) | 0 | 0 (0) | 38 | 19 (50) |
2020 | 13 | 4 (31) | 0 | 0 (0) | 13 | 4 (31) |
2021 | 5 | 2 (40) | 0 | 0 (0) | 5 | 2 (40) |
Total | 111 | 46 (41) | 0 | 0 (0) | 111 | 46 (41) |
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
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Eastern equine encephalitis virus disease cases reported to CDC by state of residence, 2012-2021
State | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | Total |
---|---|---|---|---|---|---|---|---|---|---|---|
Alabama | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 2 |
Alaska | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Arizona | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Arkansas | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
California | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Colorado | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Connecticut | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 4 | 0 | 0 | 5 |
Delaware | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Dist. of Columbia | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Florida | 2 | 3 | 0 | 0 | 0 | 1 | 3 | 0 | 0 | 0 | 9 |
Georgia | 1 | 1 | 0 | 0 | 1 | 2 | 1 | 1 | 0 | 2 | 9 |
Hawaii | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Idaho | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Illinois | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Indiana | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 2 |
Iowa | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Kansas | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Kentucky | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Louisiana | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Maine | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 2 |
Maryland | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 |
Massachusetts | 7 | 1 | 0 | 0 | 0 | 0 | 0 | 12 | 5 | 0 | 25 |
Michigan | 0 | 0 | 1 | 0 | 2 | 0 | 1 | 10 | 4 | 1 | 19 |
Minnesota | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Mississippi | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Missouri | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Montana | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 |
Nebraska | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Nevada | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
New Hampshire | 0 | 0 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 |
New Jersey | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 4 | 0 | 0 | 5 |
New Mexico | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
New York | 0 | 0 | 2 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 5 |
North Carolina | 2 | 1 | 0 | 1 | 2 | 0 | 0 | 1 | 0 | 1 | 8 |
North Dakota | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Ohio | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Oklahoma | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Oregon | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Pennsylvania | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 |
Puerto Rico | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Rhode Island | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 0 | 0 | 3 |
South Carolina | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
South Dakota | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Tennessee | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 |
Texas | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Utah | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Vermont | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 |
Virginia | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Washington | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
West Virginia | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Wisconsin | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 2 | 1 | 4 |
Wyoming | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Total | 15 | 8 | 8 | 6 | 7 | 5 | 6 | 38 | 13 | 5 | 111 |
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
To request data for previous years, please email dvbid2@cdc.gov.