Yellowstone County health officials warned Wednesday that the county has recently seen a noticeable increase in shigella infections.

Shigella is a bacteria found in the stool of infected people and is passed on via a fecal-oral route or by eating or drinking contaminated food or beverages, a news release from RiverStone Health, the county’s public health agency, said.

As of Wednesday, five cases had been confirmed and two more were pending. Typically, Yellowstone County sees only one or two cases annually.

“Five reported cases of shigella infection may not seem large, but we estimate that for every reported case, the actual number of cases could be 20 times greater,” said John Felton, RiverStone’s president and CEO and Yellowstone County’s health officer.

Eight more cases have been confirmed around the state by the Montana Department of Public Health and Human Services. Montana usually sees about 11 cases a year.

Symptoms can include bloody diarrhea, fever and stomach cramps and can appear 12 to 96 hours after infection, RiverStone said.