(CNN) A mother said her son was covered in wounds from flesh-eating bacteria the day after a swim off the coast of Maryland, according to CNN affiliate WJZ in Baltimore. Peninsula Regional Health System physicians diagnosed the boy with Vibrio, Brittany Carey shared in a Facebook post on Saturday.

Vibrio causes an estimated 80,000 illnesses and 100 deaths in the United States every year, according to the US Centers for Disease Control and Prevention. People with vibriosis become infected either by consuming raw or undercooked seafood or by exposing an open wound to seawater.

In her post, Carey explained that her parents took her son swimming last Monday in a small bay near Ocean City, close to the Harry W. Kelley Drawbridge on Route 50. Later that evening, "I started noticing little spots developing all over his body," Carey wrote.

The following morning, "there were open wounds developing," she said. She believed that her son had been scratching the spots, "making them worse." Later, though, she discovered the wounds had grown larger and increased in number.

"Off to the hospital we went," she said. There they were told "it was really nothing," and this was followed by a prescription for "an antibiotic that only made it worse." A second visit to Peninsula Regional Health System came up with the right diagnosis and treatment.

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