AUGUSTA, Maine — The E. coli infection that killed one Maine toddler and hospitalized another in October cannot conclusively be tied to the county fair both boys visited, the Maine Center for Disease Control and Prevention announced Friday.
The children, who separately attended the Oxford County Fair, were infected with the same strain of E. coli, making it “highly likely” they acquired the illness from the same source, according to state health officials.
But that strain was not detected in any samples tested in state or federal labs, Maine CDC said in a news release.
“Additional investigation of other potential causes was also inconclusive, and the Maine CDC has closed its investigation and labeled the cause of these cases undetermined,” the release states.
A petting zoo at the fair had been the only reported link between the two cases. Parents of both children have said each boy developed hemolytic uremic syndrome, a condition that can cause kidney failure and is usually linked to E. coli infection.
While many strains of E. coli are harmless, some produce dangerous “Shiga toxins” that can lead to life-threatening complications.
“The reality is that the majority of cases we investigate end up with an undetermined cause,” state epidemiologist Dr. Siiri Bennett said in the news release. “While we know the two children were infected by the same molecular strain of Shiga-toxin producing E. coli, or STEC, that same strain was not found in any of the samples that we tested here in Maine or in the samples we sent to the U.S. CDC.”
The strain identified in the two boys’ cases, known as O111, is one of several that can cause illness.
One sample collected from animal pens adjacent to a barn area at the fair tested positive for Shiga-toxin producing E. coli, but the U.S. CDC confirmed it didn’t match the strain that caused the boys’ illness.
A second sample from the petting zoo area tested positive for Shiga toxins at the state lab, though E. coli was not identified, Maine CDC said. Federal health officials repeatedly tested the same sample, also finding none of the bacteria.
Maine CDC and the Maine Department of Agriculture, Conservation and Forestry also tested common food items from the fair, which ran Sept. 16-19 in the town of Oxford. None was identified as the likely cause of the illness.
E. coli is most commonly transmitted by consumption of contaminated food or water, but it can also be contracted through contact with farm animals. The bacteria often live in the digestive systems of humans and other mammals. People typically contract the bacteria by coming in contact with animal feces, then eating or touching their mouths with contaminated hands.
Hemolytic uremic syndrome affects 5 to 10 percent of those diagnosed with E. coli-produced shiga toxin, according to the U.S. CDC. Early symptoms of the syndrome include diarrhea, vomiting, abdominal pain, fatigue, pale skin and unexplained bruises or bleeding from the nose and mouth. Neurological problems also may develop, including seizures.
People with compromised immune systems, such as young children and the elderly, are more likely than others to develop severe illness from E. coli and hemolytic uremic syndrome. While most people recover from that complication within a few weeks, some develop kidney failure that leads to permanent damage or death.
Health officials recommend cooking meat and washing produce thoroughly to fend off foodborne E. coli, as well as washing hands after touching raw food or live animals.
The bacteria can spread to fruit and vegetables through fertilizer or contaminated water.