Shigellosis cases continue to rise in Louisville, with 18 laboratory-confirmed cases last week.

That’s the highest number in any week so far during the current outbreak, which has seen 84 confirmed cases in 13 weeks.

Shigellosis is a highly-contagious diarrhea illness caused by Shigella bacteria. Symptoms include watery or loose stools for several days, and in severe cases abrupt onset of fever, nausea, abdominal cramping and vomiting.

For the past five years, Louisville has had an average of 62 confirmed cases annually.

To prevent the illness, health officials are urging people to wash their hands carefully with soap and water, including under the fingernails. This is especially important after handling items such as diapers, after each bowel movement, after helping children use the toilet and before preparing or eating food, health officials said.