Bacteria with potentially fatal consequences inhabit the Chesapeake Bay and other warm U.S. coastal waters every summer, but the Vibrio family rarely makes headlines.

That perplexes Ken Smith, a Northumberland County waterman who had plenty of time for thought during a four-day hospital stay for treatment of a Vibrio-induced illness he contracted after crabbing on the Rappahannock River.

"If someone gets bit by a shark in Florida, it gets national coverage by every newspaper and television station across the country," he said in an e-mail after he left Rappahannock General Hospital on June 28. "Yet when we have something that will kill you just as dead as a shark or limbs are amputated, we hear very little."

On average, 50 Vibrio infections are confirmed each year in the U.S. They result in an average 16 deaths and 45 hospitalizations, according to the Centers for Disease Control and Prevention.

By contrast, shark attacks are extremely rare. According to the Florida Museum of Natural History, the last reported death in the nation attributed to a shark was one in Florida in 2005, a year when 40 attacks were reported in the U.S.

Still, the odds of encountering Vibrio are slim. Howard Kator, an associate professor at Virginia Institute of Marine Science who has studied Vibrio, doesn't think twice about getting into the water.

"Unless something really changes, I wouldn't necessarily worry," he said. "Think of all the people that go into the water -- there's a very low incidence of these things."

A commercial waterman, Smith woke up the day after fishing his crab pots to find a rapidly swelling knot on his right arm.

"It started as nothing but a little dot on my arm, but within 20 minutes it was the size of an egg and in the next 10 or 15 minutes I was shaking like I was in convulsions," Smith said.

When he checked into the hospital a short while later, he had a 103-degree fever. Doctors treated the infection with antibiotics.

Experts surmise that Smith became infected with Vibrio vulnificus through a cut.

"It gets into the bloodstream and reproduces very quickly, causing massive swelling," Kator said. "If it gets too far, it can require amputation to stop it from spreading."

The other way that people can be infected is by eating raw or undercooked seafood -- especially raw oysters -- that have filtered cells of Vibrio vulnificus or its relative, V. parahaemolyticus, from the water. Thorough heating kills the bacteria.

The food-borne variety of Vibriosis is potentially the most dangerous, said Robert Croonenberghs, director of the Virginia Department of Health's Division of Shellfish Sanitation.

Healthy individuals can experience vomiting, diarrhea and abdominal pain, according to the CDC. In immunocompromised people, especially those with chronic liver disease, Vibrio can infect the bloodstream, causing "a severe and life-threatening illness characterized by fever and chills, decreased blood pressure and blistering skin lesions." CDC's Web site says that Vibrio vulnificus bloodstream infections are fatal about 50 percent of the time.

The Interstate Shellfish Sanitation Conference, which seeks to safeguard the nation's seafood supply, advises people with immune system problems to avoid eating raw seafood, said Ken Moore, the group's executive director.

The group also has encouraged seafood packers on the Gulf Coast, where Vibrio is present for longer times of the year, to chill or steam oysters to kill the bacteria. About 15 percent of oysters shipped out of the Gulf are treated this way, Moore said, and demand for the process is growing.

The last case of Vibriosis traced to a Virginia oyster originated with one harvested from the James River in 2006, Croonenberghs said. The person lived.

Virginia upgraded its summertime harvesting rules by requiring that oysters be refrigerated by 10 a.m., before the heat of the day, to prevent the growth of Vibrio cells.

The bacteria occur naturally in warm saltwater. U.S. incidents peak between June and September, according to the CDC.

"Pollution has no bearing on the number of Vibrio found in the water," said Seth Levine, a food-borne disease epidemiologist with the Virginia Department of Health.
Contact Lawrence Latané III at (804) 333-3461 or llatane@timesdispatch.com.