Navy medical researchers have expanded the knowledge of the bacterium that causes "travelers' diarrhea" and are in the early stages of clinical trials of a vaccine they developed for it.

Recognizing the impact of travelers' diarrhea on military readiness, particularly when it affects deployed forces, the Defense Department is the primary sponsor of the research, with assistance from other groups, said Navy (Dr.) Capt. Stephen Savarino, and clinical trial principal investigator Navy Cdr. Mark Riddle of the Naval Medical Research Center at the Forest Glen Annex here.

The bacterium was discovered as the cause of travelers' diarrhea in the late 1960s by other researchers, and Naval Medical Research Center researchers developed the first vaccine in 2004. After toxicology studies in 2011, they started the first phase of clinical trials in August, Riddle said. Forty volunteers ages 18 to 45 are participating.

With the trials just beginning, Savarino said, more work remains to be done before the vaccine will be available, The Food and Drug Administration requires all new drugs to be proven safe and effective before they're administered to people, he explained, and though clinical data from this trial area is expected this year, it could be seven or eight years before the vaccine is licensed.

"We think there's a lot of promise in this vaccine," he said, "but we need to have the data to support it moving forward."

The E. coli bacterium that causes traveler's diarrhea often develops ¬during visits to parts of the world where sanitation is not as sophisticated as the U.S. public health system, the researchers said. Savarino added that even those who try to practice the best hygiene possible in these countries still are susceptible.

Largely picked up by consuming contaminated water or food, the condition is so common for Americans that many service members don't seek treatment for it, the researchers said, though it can have a severe impact on their mission.

"When we send forces to places like Iraq or Afghanistan, ... the risk of disease can run 30 percent to 50 percent per month," Savarino said, and the impact is particularly severe during the first six to 12 months of a deployment. "That's when the rates of disease are extremely high," he said.

Even a sole service member with diarrhea can hurt military operations, Riddle said.

"You're deployed to places where the temperature can be 140 degrees, and you have to use the bathroom six times a day," he said. "You've got cramping, abdominal pain and nausea, and you're operating a tank, or on patrol, worried about an improvised explosive device. How well are you able to do that job, protect yourself and your fellow troops, when you're preoccupied with an illness like that?"

Riddle acknowledged that no one has died in Iraq or Afghanistan because of diarrhea -- at least directly.

As researchers work toward a licensed vaccine, they recommended some precautions U.S. service members and the traveling public can take to avoid travelers' diarrhea.

In addition to maintaining good hygiene, Savarino said, people "must stay hydrated, eat well and remember that electrolytes are important."

Drinking water is vital, he emphasized. "Dehydration can be a problem in the military, because troops are running hard all the time," he said. Other factors that also play a part include prior exposure, genetics, what one eats, and the amount of healthy bacteria in the body.