Encephalitis has claimed three lives and been confirmed in six other cases, prompting an expansion of the city's efforts to wipe out the mosquito-borne disease.
City officials announced Wednesday they would spray schools and continue spraying nonresidential areas in Queens and the Bronx with the pesticide malathion.
The U.S. Centers for Disease Control and Prevention confirmed four more cases of St. Louis encephalitis in the city Wednesday, including two in eastern and central Queens and one in Brooklyn.
City health officials said the virus, which had previously only been confirmed in Queens, may be spreading.
They said malathion would be hand-sprayed overnight at public schools in the affected areas of Queens, but spraying wouldn't begin in Brooklyn until further evidence indicates a need. They said said malathion "poses virtually no risk to humans and pets," but anyone who lives near the areas being sprayed should stay inside during spraying hours in the evening.