State health official announces probable case of human West Nile virus The South Dakota Department of Health announced Aug. 21 the state's first probable human case of West Nile virus. A blood sample from a 64-year-old resident of Carthage in Miner County has tested positive at the State Public Health Laboratory. The individual is hospitalized in a Sioux Falls hospital in serious condition. The infection appears to be locally acquired.
"Given the number of West Nile positive birds and horses detected across South Dakota, it's not unexpected that a human case would be identified," said Doneen Hollingsworth, secretary of health. "The risk of human illness is low but it does increase as the intensity of animal infection increases. That's what we're seeing in South Dakota now that the virus has been detected in 40 counties."
Hollingsworth emphasized the risk to humans is still low and that most of those who become infected will not become ill. Some may develop mild flu-like symptoms such as fever, headache, body aches, and occasionally swollen lymph glands or a rash. In rare cases West Nile may cause encephalitis, or inflammation of the brain. Individuals with severe or unusual headaches should seek medical care as soon as possible.
"The last reported human cases of mosquito-borne viral encephalitis in South Dakota were in 1988 (one case) and 1984 (two cases) of Western Equine Encephalitis. In the 1970s there were also human cases of St Louis Encephalitis in the state. Since 1988 there have been no reported cases of mosquito-borne encephalitis in South Dakota," said Hollingsworth.
New test results this week show the virus in 10 counties where it has not been reported before, including Clark, Clay, Deuel, Hand, Jackson, Jones, Lyman, Pennington, Sully, and Yankton counties. A total of 50 birds, 120 horses and one sampling of mosquitoes have tested positive.