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North Dakota Encephalitis Epidemic


To combat North Dakota’s western equine encephalitis epidemic in 1941, health authorities recommended that farm workers wear mesh veils, gloves and ankle coverings. That’s because the outbreak was linked to mosquitoes transmitting a virus from horses.

Encephalitis causes inflammation of the brain, flu-like symptoms, weakness and loss of consciousness. The so-called “sleeping sickness” had been present in the state since the ‘30s, but nothing like the epidemic of 1941, which affected at least eleven hundred North Dakotans, killing at least 130.

The epidemic began in early July when four people in Cass County were hospitalized. In Jamestown a farm family was sickened, and several of their horses died. A week later, 21 people were hospitalized in Fargo. 

Health authorities strived to clean up mosquito breeding places, and a Bismarck filling station owner donated 200 gallons of used crankcase oil to pour around a local reservoir to help combat the mosquitoes. 

The disease appeared across the state, from Carpio to Christine, Hettinger to Hebron, Wilton to Wing. Dozens of people were hospitalized, some in critical condition.

By mid-August, the epidemic reached a peak of 340 cases in one week. Stutsman, Cass and Bottineau counties were hot spots. State and federal health authorities met in Fargo to discuss research into the regional epidemic, which stretched across the northern plains from Nebraska to Manitoba. 1941 was a record-wet year for North Dakota, which favored mosquitoes.

Aside from the body coverings, health authorities also recommended that farm workers do their chores during “a breezy time of day.” Other recommendations were to install screens over porches and openings to houses, and to drain or treat standing water. There were similar measures for protecting horses, such as screens and isolating animals. More than 2,500 North Dakota horses were sickened, and more than 500 died.

On this date in 1941, the epidemic was waning, likely due to cold weather. For the first time in months, encephalitis was no longer the leading communicable disease in the state. Health officials were anxious, however, about the prospect of the disease returning the following year, but in 1942 only 24 cases were reported.

Dakota Datebook by Jack Dura

The Bismarck Tribune. 1941, June 12, page 4
The Bismarck Tribune. 1941, July 7, page 2
The Bismarck Tribune. 1941, July 8, page 1
The Bismarck Tribune. 1941, July 12, page 1
The Hope Pioneer. 1941, July 14. Page 4
The Bismarck Tribune. 1941, July 15. Page 3
The Bismarck Tribune. 1941, July 22. Page 3
The Hope Pioneer. 1941, July 24. Page 4
The Bismarck Tribune. 1941, August 2. Page 5
The Bismarck Tribune. 1941, August 7. Page 1
The Hope Pioneer. 1941, August 14. Page 8
The Bismarck Tribune. 1941, September 16. Page 2
The Bismarck Tribune. 1941, September 30. Page 2
The Bismarck Tribune. 1941, December 26, page 2
The Bismarck Tribune. 1942, July 16. Page 10
The Bismarck Tribune. 1942, October 21. Page 6
Thirty-sixth Annual Report of the State Livestock Sanitary Board to the Governor of North Dakota. (1942).
Public Health Reports, 1959 Index, Vol. 74, No. 12, January-December and Public Health Monographs, Numbers 56-60
Ogden, L.J. (1970). Vector and vector-borne disease problems associated with water and related land resources. U.S. Department of Health, Education and Welfare, Public Health Service


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