New West Nile case numbers slow down in South Dakota

New West Nile case numbers slow down in South Dakota The Department of Health reported 16 more human West Nile cases Oct. 17, the least number of new cases reported since early August. There have been a total of 1,035 cases and eight deaths reported in South Dakota. Nationally 6,977 West Nile cases, including 149 deaths, have been reported to the Centers for Disease Control and Prevention.

West Nile disease cases have been reported from every county in South Dakota. Counties with the highest number of cases include Pennington (133), Brown (82), Minnehaha (57), Hughes (43), Butte (41), Lawrence (29), Charles Mix (27), Meade (26), Shannon (24), Dewey (23), Fall River (23), Marshall (21), Davison (20) and Turner (20). The eight deaths occurred in Brown, Clay, Meade, Pennington (3), Shannon and Ziebach Counties. The Department of Health has also reported 89 out-of-state West Nile disease cases to their home states.

Of South Dakota's cases, 143 have been reported with meningitis, encephalitis or meningoencephalitis; 740 with West Nile fever; and 17 with acute flaccid paralysis syndrome associated with WNV infection. Many cases are still under investigation or have a pending diagnosis. Fifty-three percent of the cases are male and 47 percent are female.

Eighty-eight percent of the cases are white and 11 percent are Native American. The median age is 44 years and the ages range from less than 1 month to 96 years. The elderly are at greatest risk of meningoencephalitis, the most severe form of WNV disease; 52 percent of the cases are over 50. The median age of the deaths is 79 years (range 34-89). The deaths are 75 percent male and 25 percent female. The South Dakota Public Health Laboratory has done 7,340 West Nile tests this year.

There have been 57 asymptomatic individuals detected through routine screening of blood donations since July in South Dakota.

One case of St. Louis encephalitis (SLE) has been reported in a resident of Hughes County. The SLE virus is in the same virus family as the West Nile virus. SLE is similar to West Nile having symptoms such as headache, fever, stiff neck, tremors, stupor and coma. SLE is transmitted from bird to mosquito to humans, like West Nile. Since 1964 there have been three cases of SLE reported in South Dakota. So far in 2003, there have been seven cases of SLE reported nationwide.

Non-human West Nile positives have included 727 mosquitoes, 131 birds, 73 ill horses, two dogs and two squirrels.

Although the risk of infection decreases with cooler fall weather, the West Nile transmission season will continue until an area experiences its first hard frost, which is a temperature of 28 degrees F or less. People are encouraged to take anti-mosquito precautions until the first hard frost hits their locality.

As the 2003 West Nile transmission season fades away all communities are encouraged to start planning local mosquito control programs for the 2004 season. The West Nile virus is now endemic in South Dakota. Personal protection and integrated mosquito controls are the primary means of preventing human disease. Integrated mosquito control methods include reducing standing waters where mosquitoes grow, killing larvae and killing adult mosquitoes by spraying.

For more information please go to the South Dakota West Nile Virus Web site, WestNile/.

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