It's very very rare but it is wise to be cautious. It's just about any big old fish in the summer months that are risky.My 16 yr old grand nephew ate a HUGE piece of mackerel, it covered the whole plate, here in August 2009 and was in ICU at Belize Healthcare Partners on life support for a week. Another person ate a small piece of the same fish and just had mild symptoms of vomiting, diarrhea and tingling extremities.Both are now fine with no lasting effects. The smaller fish and barracuda under 5 lbs are not carriers and are safe.