Exposure to seawater proves deadly.

In the wake of Hurricane Katrina, open wounds exposed to brackish seawater along the Gulf Coast have led to six deaths and 24 other severe infections from Vibrio bacteria, report researchers at the Centers for Disease Control and Prevention (CDC) in Atlanta.

Nineteen varieties of Vibrio bacteria are found naturally in warm seawater, and they cause roughly 400 infections in the United States each year, CDC data show. Most of these infections result from Vibrio microbes ingested by people eating raw shellfish. Those cases are rarely fatal.

However, one-fourth of Vibrio infections arise from subspecies that pass through the skin via scratches, cuts, or abrasions. Among these, infection by Vibrio vulnificus is the most serious, says CDC internist Amy M. Dechet.

The spate of Vibrio infections soon after Hurricane Katrina is probably attributable to people's increased contact with brackish seawater, Dechet says. People who were treated with antibiotics within a day or two of exposure were routinely cured. Those who died or lost limbs were not hospitalized until more than 2 days after redness appeared, Dechet says.

"We certainly don't recommend people avoid the beach" Dechet says. But if after contact with ocean water, a person notices a cut "that's red and angry for 24 hours, see a doctor," she says.--N.S.