Service personnel returning from Operation Desert Storm run the risk of carrying home exotic diseases from the Persian Gulf area that can take months or years to surface, doctors warned.

Although most members of the military are likely to come back healthy, a few could bring home diseases not found in the United States but common to the gulf region, Col. Charles Oster and colleagues at Walter Reed Army Medical Center in Washington said Wednesday.Doctors who treat veterans of the gulf conflict should be alert to the possibility they could be suffering from diseases with names such as sandfly fever, leishmania and Congo-Crimean hemorrhagic fever, they said.

Particularly in the case of reservists, some will come back "with diseases that only become evident after their homecoming, sometimes after months or years," the doctors wrote in The New England Journal of Medicine.

Veterans who carry such disorders also could "pose a risk of secondary transmission to people with whom they come in contact," they added.

The largest threat by far to soldiers or any other visitors to the Middle East are common intestinal disorders largely caused by bacteria, salmonella or viruses, Oster said.

Incidence rates for these illnesses "have been as high as 50 cases per 1,000 American troops per week in Saudi Arabia," he said.

One frequent cause of acute diarrhea in the region is giardia, a parasitic intestinal infection that in recent years has become increasingly common in the United States, he said.

In addition, 9 percent of patients seen at medical centers in Riyadh, Saudi Arabia, harbored amoeba organisms that cause diarrhea and other intestinal symptoms, Oster said.

In most cases, standard antibiotic treatments are effective in clearing up intestinal infections, he said. But he added that is not the case for those caused by bacteria.

"Apparently, years of indiscriminate use of antibiotics in the Middle East have selected bacterial populations with extremely high rates of resistance to multiple antibiotics," he noted.

Although intestinal illnesses generally have short incubation periods, Oster said the parasitic infection leishmania - which is transmitted by sandflies - can take years up to 20 years to surface in the form of symptoms including fatigue, weight loss and anemia.

Much more common than the type of leishmania that involves internal organs is a form that affects the skin and is "often referred to locally as Baghdad boil," he said.

"There are thousands of cases a year in Saudi Arabia and incidence rates of over 50 percent have been documented in exposed foreigners who are not immune," Oster noted.