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Doctors have tried for years to prevent, or at least reduce, the ravages of St. Louis and other forms of insect-borne encephalitis. But the disease is difficult to treat or eradicate. No effective way has been developed to immunize people against it. Health officials are concentrating on spraying and swamp-drainage programs aimed at cutting down the number of mosquitoes, for the only known way to prevent encephalitis is to eliminate the pesky insects that transmit it.
* So-called because the virus was first isolated from brain-tissue specimens in a St. Louis laboratory in 1933.