Doctors in Orlando diagnosed a seventh child with a potentially fatal kidney ailment Wednesday in a widening medical mystery that has left health officials dumbfounded.
The child, as well as others admitted to hospitals in the past week, is in critical condition with kidney failure after visiting a petting zoo in recent weeks.
Investigators are checking to see if the children became sick from bacteria that can be found in animal feces. Sources said other than petting-zoo animals are being explored, and doctors say they won't be surprised if more sick children show up at area hospitals.
"We are ready for any number of cases," said Dr. Mehul Dixit, a pediatric nephrologist with Florida Hospital Orlando, where four children are being treated. "We will make all necessary arrangements to make sure they get the care they need."
The children are suffering from an uncommon condition called HUS, or hemolytic uremic syndrome, which causes the kidneys to malfunction.
Of the four children at Florida Hospital, three were listed in critical condition Wednesday, with one child on dialysis.
The fourth child's condition improved from critical to guarded.
Two more children in critical condition are receiving care at Arnold Palmer Hospital for Children & Women, where the new case was identified Wednesday night.
A seventh child was treated at Arnold Palmer several weeks ago, and it is not clear if that case is connected to the others.
The children currently hospitalized all touched animals recently at area fairs, including the Central Florida Fair in Orlando and the Florida Strawberry Festival in Plant City. Both events were held March 3-13.
Another possibility is that the children were exposed to trouble-causing bacteria through contaminated food or beverages.
Health officials are interviewing family members to retrace meals in recent days and glean other information to nail down a cause.
"We don't know yet what the common denominator is," said Joann Schulte, a medical epidemiologist with the Florida Department of Health in Tallahassee.
"Certainly, the petting zoos are of interest, but we don't know if they're the source" of the infections.
For now, doctors are helping the patients with treatments such as intravenous liquids, blood transfusions and dialysis to ease the strain on the kidneys.
Many children with HUS recover without lasting effects, but some die or suffer permanent kidney damage that could require dialysis later in life.
At least three of the children are undergoing dialysis treatments, according to doctors. Sung Kim and his wife stayed Wednesday at the bedside of their 6-year-old son in Florida Hospital Orlando, encouraged that he would survive.
Doctors told them the boy's kidney function had improved from 50 percent to 60 percent.
"We are lucky; we are luckier than others," said Kim, who lives in Heathrow.
His son spent time last week feeding goats and calves at the Central Florida Fair, alongside his younger sister, who has not become sick.
The condition is most often caused by a specific form of the Escherichia coli bacteria that live in the intestinal tracts of many animals.
This form -- E. coli O157:H7 -- has been linked to outbreaks of kidney failure among children in other states, including Pennsylvania, North Carolina and Washington.
Health officials traced those outbreaks to contact with farm animals.
In the Florida cases, however, not all children have tested positive for E. coli. That could indicate a source other than farm animals as the cause of their infections.
Health officials are retesting the children for E. coli and are awaiting those results from a state lab in Jacksonville and the Centers for Disease Control and Prevention in Atlanta.
Once a child is infected, he or she typically suffers from a bout of diarrhea that can last several days.
After it clears up, the child remains tired, pale and irritable.
Kim said that is precisely what happened to his child.
Inside the body, a toxin produced by the E. coli attacks red blood cells, sometimes causing fragments of the cells to clog the tiny vessels in the kidneys. The kidneys stop functioning normally, and the child begins to show decreased urination and puffiness as liquids in the body are not regulated properly.
Doctors said parents should be mindful of these symptoms.
"If you have a child with diarrhea and a history of being at one of these petting zoos, you should contact your physician," said Dr. Jorge Ramirez, a pediatric nephrologist with Arnold Palmer and the Nemours Children's Clinic.
Robyn Shelton can be reached at rshelton@orlandosentinel.com or 407-420-5487.