Animal and Plant

Health Inspection

Service 2020 Summary of Eastern Equine

Veterinary Encephalitis Cases in the United States

Services

January 1 – December 31, 2020

February 2021

This report is a descriptive summary of U.S. Eastern equine encephalitis (EEE) cases reported to the

United States Department of Agriculture (USDA) in 2020. The USDA Animal and Plant Health Inspection

Service (APHIS) Veterinary Services (VS) branch collaborates with the U.S. Centers for Disease Control

and Prevention (CDC) and State veterinary and public health officials to facilitate communication about

arbovirus disease cases in horses and confirm equine cases in each State. CDC collects arbovirus case

information using its ArboNET reporting system, an electronic surveillance and reporting system for

tracking and reporting arboviral activity in humans and animals. During the transmission season, VS

disseminates the equine arbovirus case information to State animal health officials for confirmation and

posts the number of confirmed cases to the USDA equine information Web site

https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/equine. This site

also provides specific case definitions. In this document, ‘reported cases’ of EEE may include

presumptive positive and confirmed positive cases.

In 2020, 142 equine cases of EEE were reported from 13 States. Figure 1 shows the annual number of

equine EEE cases reported in the United States from 2007 through 2020. Figure 2 shows the number of

equine EEE cases in each State in 2020, and Table 1 provides the number of cases per county or parish in

those States in 2020.

Equine Cases of EEE

350

301

300

86

118

136

192

209

142

185

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

247

250

206

184 200

150

107

100 70 60

50

0

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

EEE Cases

Figure 1. Reported U.S. equine cases of Eastern equine encephalitis, 2007-2020
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2020 Summary of Eastern Equine Encephalitis Cases in the United States

Figure 2. Distribution of reported equine EEE cases in 2020 (142 total cases)

Table 1. Number of reported equine EEE cases by State and county, 2020

State County Eastern Equine Encephalitis

Reported Cases

Florida Baker County 2

Bradford County 2

Clay County 1

Gilchrist County 1

Hendry County 2

Holmes County 4

Jackson County 2

Lake County 1

Marion County 1

Orange County 2

Polk County 1

Putnam County 1

USDA-APHIS-VS 2
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2020 Summary of Eastern Equine Encephalitis Cases in the United States

State County Eastern Equine Encephalitis

Reported Cases

Santa Rosa

County

1

Volusia County 1

Total Cases for Florida 22

Georgia Irwin County 1

Long County 1

Lowndes County 1

Thomas County 1

Tift County 1

Total Cases for Georgia 5

Indiana Kosciusko County 1

Lagrange County 2

La Porte County 1

Total Cases for Indiana 4

Louisiana Iberville Parish 1

Lafayette Parish 1

Lafourche Parish 3

St. Martin Parish 1

Total Cases for Louisiana 6

Michigan Baraga County 1

Barry County 1

Calhoun County 1

Clare County 5

Gladwin County 1

Ionia County 2

Isabella County 1

Jackson County 2

Kent County 4

Livingston County 2

Mecosta County 1

Menominee

County

1

Montcalm

County

8

Newaygo County 2

Oakland County 4

Tuscola County 1

Total Cases for Michigan 37

Minnesota Aitkin County 1

Benton County 1

Total Cases for Minnesota 2

USDA-APHIS-VS 3
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2020 Summary of Eastern Equine Encephalitis Cases in the United States

State County Eastern Equine Encephalitis

Reported Cases

New Jersey Atlantic County 1

Total Cases for New Jersey 1

New York Jefferson County 7

St. Lawrence

County

1

Total Cases for New York 8

North Carolina Bladen County 1

Brunswick

County

1

Camden County 1

Columbus County 2

Durham County 1

Johnston County 1

Robeson County 1

Total Cases for North Carolina 8

North Dakota McKenzie County 1

Total Cases for North Dakota 1

South Carolina Aiken County 3

Berkeley County 1

Clarendon

County

1

Colleton County 2

Florence County 1

Horry County 4

Jasper County 1

Lexington County 2

Marion County 1

Williamsburg

County

1

Total Cases for South Carolina 17

Virginia Accomack County 1

Chesapeake City 1

Falls Church City 1

Suffolk City 2

Total Cases for Virginia 5

Wisconsin Chippewa County 4

Clark County 1

Dunn County 3

Forest County 1

Langlade County 1

Lincoln County 1

Oconto County 1

USDA-APHIS-VS 4
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2020 Summary of Eastern Equine Encephalitis Cases in the United States

State County Eastern Equine Encephalitis

Reported Cases

Oneida County 3

Pepin County 1

Polk County 1

Price County 2

Rusk County 1

Shawano County 2

Sheboygan

County

1

Taylor County 3

Total Cases for Wisconsin 26

Total Reported Eastern Equine Encephalitis Cases for the

United States

142

EEE is a deadly disease in equids, where mortality rates can approach 90 percent in unvaccinated

animals. This susceptibility to the virus makes equids a recognized EEE sentinel species for the human

population. The main public health purpose of confirming and reporting equine EEE cases is to inform

human surveillance efforts. Because equine commercial vaccines are available and convey good

protection against EEE infection, reported cases of EEE in equids tend to be in unvaccinated or undervaccinated animals.

USDA-APHIS-VS 5