GRAYSON COUNTY, TEXAS -- It started among students at Sherman ISD, spread to Denison ISD and then to people in Van Alstyne and Pottsboro.
Three hundred people are now suspected of having shigella in Grayson County, according to health officials.
One of the most recent confirmed cases is a 5-year-old girl at Bells elementary school. Now there are concerns her classmates could become infected.
"We'll have to take steps, necessary steps to try to prevent that from happening because it is highly contagious from what I understand," Bells ISD Superintendent Joe Moore said.
Bells ISD tried to prevent the spread of shigella by sending out a memo to parents following the outbreak at Sherman ISD in October.
"...The precautions to take and the symptoms and, you know, just gave them the alert to be watching for," Moore said.
Shigella is still spreading.
The health department says shigella is contracted through ingestion and causes severe diarrhea, fever and abdominal pain.
"It's important that once they experience those shigella-like symptoms that they report them," Amanda Ortez with the Grayson County Health Department said.
Shigella is even taking higher priority than the flu in Grayson County.
"We have the majority of our personnel resources at the Grayson County Health Department at this time on the shigella project team," Ortez said.
Moore asks Bells students and staff to keep washing their hands, while the district is doing their part.
"We will wipe down door knobs, desks, bus seats, you know, anything that kids come in contact with a couple of times a day," Moore said.