NEW YORK (CBSNewYork) — Four neighborhoods on the Upper West Side were sprayed overnight with pesticide to try to reduce the mosquito population and the potential spread of West Nile Virus.

The trucks rolled out on streets between West 97th and West 58th streets from West End Avenue to West Drive in Central Park.

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The operation is in response to what federal researchers have called the worst outbreak of West Nile since 1999, with 13 cases in New York City, including five in Manhattan.

Health officials said the chances of getting sick from the spray is low, but Assemblywoman Linda Rosenthal wants more details.

“We need more information from the city, particularly what blocks were West Nile carrying mosquitos found, because on these blocks people should take more precautions,” she said.

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Some symptoms of West Nile include headache, tiredness and body aches. Occasionally, people also experience a skin rash and swollen lymph glands.

“People should be taking precautions so that they’re less likely to be bit by mosquitoes that carry West Nile. That’s limiting your time outdoors in the evening hours when they might be bit and covering up so that they have less exposed skin and using insecticide,” New York City health commissioner Dr. Thomas Farley said earlier this week.

About one in 150 patients become seriously ill. Long term effects include blurred vision, kidney disease and paralysis.

Nationwide, cases are up a staggering 40 percent since just last week. Officials said pregnant women and children are more susceptible.

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