An outbreak of hand, foot, and mouth disease (HFMD) has hit Tennessee, affecting dozens of schools in Shelby County, which includes the city of Memphis.

The county health department said cases were first identified in August, but health officials were not notified until early September.

Since then, 31 schools and three child care centers have been affected and at least 178 students and staff members have fallen ill, according to an update from the Shelby County Health Department (SCHD).  

SCHD said it is working closely with schools and child care providers to monitor cases and prevent further spread.

The department did not list the schools affected, but at least one is Sherwood Elementary in Memphis, according to local ABC News affiliate WATN-TV.

Parents received alerts about HFMD cases through email, robocalls and text messages with district officials saying extra steps were being taken to disinfect classrooms, WATN reported.

HFMD is a disease that is most common in children under 5 years old, according to the Centers for Disease Control and Prevention.

Most patients have mild symptoms for seven to 10 days, which can include fever, sore throat, painful mouth sores that blister and a rash on the hands and feet, the CDC said.

HFMD is very contagious and can spread when people come into contact with droplets from a person sneezing, coughing or talking; objects and surfaces that have virus particles; fluid from blisters; and feces, according to the CDC.

“While most cases of hand, foot, and mouth disease are mild, the virus spreads easily in group environments like schools and day cares,” Dr. Bruce Randolph, SCHD director and health officer, said in a press release. “Parents should keep sick children home until they are fever-free, feeling well, and any mouth sores or blisters have improved.”

To prevent the spread of HFMD, the CDC recommends washing hands often with soap and water for at least 20 seconds, helping children wash their hands, avoid touching the face with unwashed hands, cleaning and disinfecting frequently touched surfaces and avoiding close contact with an infected person.

There is currently no treatment specifically for HMFD. Patients usually recover on their own and can take steps to manage symptoms, including using over-the counter medications for pain and fever and making sure to stay hydrated.

Because HFMD normally causes mild illness, the CDC says children can continue to attend school or child care centers as long as they don’t have a fever, have no uncontrolled drooling from mouth sores and feel well enough to be in class.

However, the agency noted that local health departments may require children with HFMD to remain home to control an outbreak.