McDonald’s Corporation (NYSE:MCD) warned its customers of possible traces of Hepatitis in its locations in central Kentucky.

The fat food chain issued the warning after a food handler worked while infected with Hepatitis A at a store location on Glades Road in Berea last month, according to the Madison County Health Department. The risk to patrons who ate at the company’s location is low, according to the health department.

Nevertheless, those who ate there on March 23 should keep a close eye out for signs and symptoms of Hepatitis A from April 7 to May 12. That McDonald’s recently received a 100% on its latest health department inspection in February, according to the health department.

Owner and operator Phil Saken said the company is fully cooperating with local and state health officials “to investigate this matter to ensure the health and safety of our employees and guests.”

“We have been informed they are investigating a single, isolated case, and the risk to guests who’ve visited our restaurant is very low,” Saken added. “We are committed to providing a clean and safe environment for all who visit our restaurant and received a 100 percent score on our most recent health inspection.”

The illness can spread when an infected person does not wash their hands after going to the bathroom and then touches objects. Food or water can also be contaminated if an ill food handler touched it.

MCD stock fell about 0.7% on Thursday.