The state's top health official said Thursday that his department has zeroed in on a single petting zoo as the likely source of the mysterious bacterial infection that has sickened nearly two dozen people across Florida.
The Ag-Venture Farm Tour is the only common link for the five victims so far who have tested positive for a specific strain of bacteria known as Escherichia coli O157:H7, said state Health Department Director Dr. John O. Agwunobi.
The announcement, which came after investigators began looking at petting zoos at the Florida Strawberry Festival and Central Florida Fair, appeared to mark a turning point in the effort to pin down the cause of the illnesses, which have mainly struck young children.
"It has become increasingly clear to us one of the few, if only, bridging events is a very specific petting zoo, Ag-Venture," Agwunobi said.
"It strengthens our suspicions."
The focus shifted almost entirely to Ag-Venture after one of the five patients turned out to have attended the Florida State Fair in Tampa in February -- and not the Strawberry Festival in Plant City or the fair in Orange County that other victims visited in March. Ag-Venture ran petting zoos at all three fairs.
E. coli bacteria are found in animal feces and improperly cooked food.
The severe diarrhea from the E. coli infection also can develop into a related and more serious condition known as hemolytic uremic syndrome, or HUS, which has struck a number of children. That ailment, which can be fatal, causes kidney failure and can require dialysis.
In another development, Agwunobi said a 12-year-old Pasco County girl's death does not appear to be related to the outbreak. The girl died after a bout of diarrhea following a visit to the strawberry festival.
Early investigation into the outbreak focused either on petting zoos or tainted food. But state inspection records showed that no single food vendor attended all the events, spokeswoman Meg Shannon said.
Still, Agwunobi cautioned that the investigation is not definitive and that there is "still a lot about this kind of outbreak that we do not know." The idea of this type of infection passing from animal to human has been known only since 1996, he said.
Researchers must now perform "extensive" recurring testing on the Ag-Venture animals, none of which has yet tested positive for the specific strain of E. coli that has made people sick. It's even possible, Agwunobi said, that the infection may not have been picked up directly from an animal. It could have been passed when someone touched a piece of equipment, or even another person.
But while the investigation is not yet complete, attorneys for those sickened already were filing lawsuits.
The first lawsuit, filed Wednesday on behalf of the families of 2-year-old Nicholas Parton and 6-year-old John Kim, accuses Ag-Venture of negligence for failing to have adequate hand-washing facilities or properly warn parents of the danger.
Attorney Mark Nation, who filed the suit in Orange County Circuit Court, said John has been discharged from the hospital with his kidneys functioning at 70 percent, and will require long-term medical care.
Nicholas remains in Florida Hospital Orlando on a ventilator, Nation said.
Even before Agwunobi's comments Thursday, Nation said he thought petting-zoo animals, rather than contaminated food, were the cause of the illness.
"Ag-Venture is the common link behind all of this," Nation said.
Ag-Venture owner Tom Umiker could not be reached for comment Thursday. He said last week that his company, which takes cows, sheep and goats to about 15 fairs a year across the country, is cooperating with the state and said he was deeply troubled by the illnesses.
Umiker said the owners of animal exhibits rely on the fairgrounds to provide hand-washing and sanitizing areas, though they also sell hand wipes.
Tricia Chace, 32, of Deltona said she saw hand wipes for sale for 25 cents when she took her 3-year-old son, Connor, and 18-month-old twins to the petting zoo at the Central Florida Fair.
But she had her own baby wipes and used those to clean their hands after the children petted and fed sheep and goats.
The children ate cotton candy after that. Three days later, Chace and her children developed severe diarrhea.
Her husband, Todd, who was with them but did not pet the animals, did not become ill.
On Thursday, after a week at Florida Hospital Orlando, twins Courtney and Cole were in stable condition.
But the Chaces were anxiously awaiting further blood tests during the next few days to determine whether the children might develop the most serious condition, HUS.
"That's the scary thing about it -- you just don't know," Tricia Chace said. "They're so tired of being poked, and they finally had to take their IVs out today because all their veins have collapsed."
Longwood attorney Scott Miller said he will file a lawsuit today on behalf of the Chace family in Orange County Circuit Court accusing Ag-Venture of negligence.
All but three of the 22 confirmed cases have been children, who are more susceptible to the bacteria. E. Coli O157:H7 hits hardest on the young, the elderly and those with compromised immune systems, said Liz Compton, a spokeswoman for the state Department of Agriculture.
"Chances are, people at some time in their lives came into contact with that strain and never knew it," Compton said.
"They just thought they were under the weather."
Also on Thursday, Agwunobi said investigators suspect that three cases are secondary, meaning they contracted the illness from another infected person, not from the primary source.
Central Florida has borne the brunt of the cases. Orange County has 11 confirmed cases, while Volusia has six and Seminole has one.
In addition, health officials are keeping an eye on 33 suspected cases.
April Hunt can be reached at ahunt@orlandosentinel.com or 407-931-5940. Roger Roy can be reached at rroy@orlandosentinel.com or 407-420-5436.