STUART (CBSMiami/AP) — Blood samples are being collected from 300 people on Florida’s Treasure Coast by public health workers after 18 cases of mosquito-borne illness were confirmed.

Starting Friday, blood samples will be collected from Rio and Jensen Beach neighborhoods where the outbreak appears to be concentrated.

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Randomly selected participants will be asked if they’ve recently suffered symptoms of dengue fever.

They’ll also be asked about their recent travel and about activities that might expose them to mosquitoes.

Health officials say all the confirmed cases were exposed to dengue in those neighborhoods. None of the patients had recently traveled internationally.

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Dengue is sometimes called “break bone fever” because of the severe joint pain it causes in extreme cases.

Other symptoms include high fever, severe headache and a rash.

It’s uncommon in the U.S.

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