PHILADELPHIA (CBS) — A Chester County man has died of a rare infection associated with shellfish.

Early last week, Oxford Area Chamber of Commerce President Jerome Rodio was helping a man with a crab trap on the Chesapeake when he cut his arm, infecting it with vibrio vulnificus, an organism associated with shellfish. The 75-year-old former Philadelphia police officer died on Thursday.

Dr. Neil Fishman, an infectious disease specialist at the Hospital of the University of Pennsylvania, says it’s rarely fatal.

“People with normal immune systems generally don’t need to worry about this type of infection,” he explained. “It most commonly causes fatal disease in people that have a compromised immune system, or, even more commonly, end stage liver disease.”

Fishman says a sign that trouble may be coming is a boil-like sore. In that case, he says, seek medical help.