Two have been hospitalized, according to Whatcom County Health officer Greg Stern.
The Whatcom County Health Department is investigating what could have caused the outbreak.
Symptoms of the illness include severe stomach cramps, diarrhea that is often bloody, and vomiting.
About 1,325 first-graders and their chaperones went to the event April 21-23 at the fairgrounds in Lynden. It was put on by the Whatcom County Dairy Women.
Five of the students who were sickened were first-graders. The sixth was an older child who was involved with the festival but didn’t go as part of a field trip.
The Milk Makers Fest introduced young students to farming. It also gave them a chance to pet farm animals, including small horses, sheep, rabbits, chickens and a calf, the dairy women wrote on their Facebook page.
Pasteurized chocolate milk was given to the children but isn’t considered a source of contamination because pasteurization destroys E. coli, according to the Facebook post.
“Nothing’s been ruled out,” Stern said on Tuesday, April 28.
Stern said the main sources for E. coli illness are contaminated food, contaminated water and contact with livestock.
“We’re investigating now to find out which, if any, of those sources they have in common,” Stern said of the cases.
He did say pasteurized milk wasn’t a “particular risk.”
“But eating with dirty hands and drinking with dirty hands is a risk,” Stern added.
There are, so far, four lab-confirmed cases of what’s known as Shiga toxin-producing E. coli. The other two had symptoms consistent with E. coli.
People can get sick within two to eight days of swallowing the bacteria, according to public health officials.
Stern said that if children who attended the event get diarrhea before May 1, their parents should call their doctor’s office for evaluation and testing. Children with diarrhea shouldn’t return to school until 24 hours after the diarrhea has stopped, health officials said.
Health officials also are monitoring the illness for possible spread to others in a household. Good hand-washing habits are a must.
“It’s a way of stopping the spread,” Stern said.
The Centers for Disease Control and Prevention said people should:
Hand sanitizers were provided for children at a number of locations during the Milk Makers Fest, including as they entered the trailer with the animals and as they left the trailer, the Whatcom County Dairy Women said.
“Our hearts and prayers go out to the children, their families and loved ones,” said Jackie Blok, president of the organization, on the Facebook post. “While we have not confirmed that this educational event is the source of the illness, we are deeply concerned for their quick recovery.”
The health department has alerted parents and guardians in Bellingham, Blaine, Ferndale, Lynden and Nooksack school districts.
Antibiotics and antidiarrheal medicine shouldn’t be used with such infections, health officials said, because they increase the risk of kidney failure.