Columbus health officials are investigating what they call an “unprecedented large number of Shigella illness” in the area.

Since the start of the outbreak, 771 cases have been diagnosed.

That’s the largest number of cases in any year in the last decade.

Shigella is a bacterium that causes an infection of the intestine called Shigellosis. It causes diarrhea which may be bloody, and can cause severe dehydration and hospitalization. Found in human feces, this bacterium can get on hands when using the toilet or changing diapers.