Published: Sep 14, 2013 10:55 PM EDT

STUART, Fla. (AP) - Public health officials are knocking on doors along Florida's Treasure Coast, alerting residents about a mosquito-borne illness.
    
Rachel Heid was one of the 18 residents who caught dengue fever. She tells WPTV (http://bit.ly/19SCoRz ) she became sick at the beginning - more than a month ago. She thought she just had the flu. Her symptoms included slight nausea and she was extremely tired.
    
Blood samples are being collected from Rio and Jensen Beach neighborhoods where the outbreak appears to be concentrated. 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.
    
Dengue is sometimes called "break bone fever" because of the severe joint pain it causes in extreme cases.

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