Rodney Donald, at MedStar Washington Hospital Center, almost lost his leg due to an infection by vibrio vulnificus, a fast moving bacteria that can cause sores, amputation and even sepsis. (Caelainn Hogan)

The last thing Rodney Donald was expecting during his family’s vacation on the Chesapeake Bay was to almost lose a leg to an aggressive bacteria growing in the brackish waters.

“I’ve grown up on the bay my whole life, and I’m 66,” said Donald, propped up in a bed at MedStar Washington Hospital Center, his right leg stretched out, swathed in bandages. “I’d never even heard about it.”

Vibrio vulnificus, of the same family as vibrio cholera, is a rapid-spreading flesh-eating bacteria that naturally occurs in saltwater or estuaries, particularly from May to October.

“We might be seeing more of it, since it is getting warmer,” said Ligia Pic-Aluas, an epidemiologist at MedStar Washington.

Total reported vibrio infections in Maryland hit a 10-year high of 57 last year vs. 25 in 2002, according to the Maryland Department of Health and Mental Hygiene.

Six cases of vibrio vulnificus infection have been reported this year, according to the Maryland Department of Health. Last year, there were 14.

The Centers for Disease Control and Prevention reports an average of 50 confirmed cases, 45 hospitalizations and 16 deaths each year along the Gulf Coast, where the pathogen is most common, and nationwide as many as 95 confirmed cases, 85 hospitalizations and 35 deaths.

The Calvert County Health Department, which has issued a vibrio vulnificus alert, confirmed five infections around the Chesapeake Bay this summer.

“It is likely that over the next few decades, if global warming continues, the vibrio will start to multiply in the tidal waters of the bay earlier in the year and will persist later into the fall and possibly the winter,” said Laurence Polsky, health officer at the Calvert County Health Department. “This will increase the number of people exposed to the bacteria over the course of the year, and the result will be a higher average number of cases as each decade passes.”

Two strains of the pathogen, vulnificus and parahaemolyticus, can be picked up from eating raw seafood, particularly oysters, causing symptoms similar to food poisoning. In high-risk areas, thorough cooking of all shellfish is recommended.

Vulnificus can cause an invasive infection of the skin when even a small cut or graze is exposed to water containing the bacteria. The first symptoms include redness or swelling of the skin, followed by lesions.

Those who harvest oysters are particularly at risk because they frequently cut their hands and legs on the sharp shells and rocks.

For most people, the bacteria usually causes only a mild skin infection or upset stomach, but in people over 60 and those with weakened immune systems or compromised liver function, the bacteria can advance rapidly, infecting and killing tissue, and eventually entering the blood stream and causing sepsis. If not treated quickly, a severe infection can result in amputation of limbs or death.

Vulnificus blood infections in people with liver disease are fatal in approximately 50 percent of cases, according to the CDC.

On the evening of July 10, after a day on the water in the Calvert Cliffs area, Donald went to bed feeling fine, only to wake at 1:30 a.m. with what felt like a fire in his right leg.

“It was real painful, and I started getting the chills,” he said. “My whole body was shaking.”

He was taken to a hospital in Calvert, where doctors suspected it was “cold foot,” a problem with blood flow.

After he was administered antibiotics and transferred to MedStar Washington by helicopter, MedStar nurse Elizabeth Swanson recognized that Donald’s condition was deteriorating.

His blood was tested, and it was discovered that he was already suffering from sepsis, and a culture showed vibrio vulnificus. Swanson had never heard of it.

“Being from Colorado, it’s not something I see often,” said Swanson, who was reached by phone. “But nurses have to advocate for patients when they notice a change, especially since within three days, patients could die or lose their legs.”

Swanson informed Pic-Aluas, who happened to be on call, that the patient urgently needed her attention.

She was quickly able to identify the signature lesions of the vulnificus infection developing on Donald’s right foot — red and bluish discoloration of the skin and large sore-like blisters.

The antibiotics administered in the first hospital, and the fact that he underwent surgery quickly to remove the dead tissue where the bacteria was still present, saved not only his foot but also his life.

A few years ago, Pic-Aluas had a patient who died from such an infection. The patient, a man in his 50s, had been sailing his yacht on the Chesapeake and had a small cut on his leg.

He put off going to a doctor when he started becoming ill, and by the time he made it to the hospital, the infection had entered his bloodstream. He died from septic shock.

“It progresses fast, so timing is crucial. Every 24-hour delay means chances are lower,” Pic-Aluas said. “It can move up a limb quite quickly.”

Polsky said 99.9 percent “of people who go into the water will be fine.”

People with cuts should avoid the water or apply bandages and use antiseptic gel afterward. If symptoms of redness or swelling develop, it is important to seek medical treatment immediately, Polsky said.

After two weeks in the hospital, with six surgeries, a skin graft and a bit of a scare, Donald was ready to go home. He said the experience will not prevent him and his family from going back to the bay next summer.