Long before West Nile virus became the mosquito-borne disease everyone worried about, another type of encephalitis, St. Louis, was infecting people in the United States.
Don't be fooled by its name. St. Louis encephalitis has been diagnosed in every region of the country -- an average of 128 cases each year since 1964, reports the federal Centers for Disease Control and Prevention. As with West Nile, the elderly and people with weakened immune systems are most at risk. The disease can be transmitted to a human only by a mosquito.
Symptoms include headache, high fever, neck stiffness and disorientation. Between 3 percent and 30 percent of cases are fatal.
The best defenses against St. Louis encephalitis are to wear long shirts and pants and to use a repellant that contains DEET, being careful to follow the directions.
