One child died and three others became ill with E. coli after coming into contact with animals on Friday at the San Diego County Fair in California.
A 2-year-old boy was hospitalized and died on Monday. A complication, the San Diego County Health and Human Services Agency said in a statement.
The other three children did not need to be hospitalized. They all attended the show from 8 to 15 June and showed symptoms from 10 to 16 June, the agency said. The four cases concerned children aged 2 to 13 years. Their names have not been published.
While investigating the source of E. coli, "all the children had a report on visiting the zoos or the petting zoo, or had other animal contacts on the San Diego Fair," the health department said.
Trade show officials have blocked public access to all animal areas including the petting zoo. More than 1 million people visited the fair, which will last until Thursday.
"Our hearts, our prayers, our thoughts are directed to the family and friends of this little child," Timothy Fennell, CEO of Del Mar Fairgrounds and General Manager of County Fair, said at a Friday night press conference. "We're devastated."
Fennell said they were notified about three E. coli cases Friday morning and learned that a child had died that evening. He said that it appears that the children were brought into contact with possibly living animals or the petting zoo.
Fennell said that the Mass would continue. "No contamination has anything to do with food services or food, which has been confirmed," he said.
The Department of Environmental Health re-examined the food facilities visited by the children and found no connection with the cases, the health department said.
There are many E. coli strains, but children were infected with Shiga toxin-producing E. coli for disease control and prevention.
"Our sympathy goes to the family of the child who has died of this disease," said District Health Department Wilma J. Wooten in a statement. "While most people recover from this disease without complications, 5 to 10 percent of STEC-diagnosed people develop a life-threatening kidney infection."
The symptoms of infections with Shiga toxin-producing E. coli can vary, but often include diarrhea, severe abdominal cramping and vomiting, according to the Health Department.
The CDC estimates that Shiga toxin-producing E. coli causes about 3,600 hospital admissions and 30 deaths annually in the US. The highest risk of serious illness is in children under the age of 5, adults over the age of 65 and those with weakened immune systems.
The county health department said the most important step in preventing infection is good hand washing hygiene, and it reminds people to always wash their hands thoroughly after contact with animals or their environment.