About 80 people in 28 states became ill in a Salmonella outbreak associated with contact with pet frogs between spring and fall 2009, according to figures from mid-December.
Samir Sodha, MD, a medical epidemiologist with the Centers for Disease Control and Prevention, said when about 50 cases had been identified that more than three-quarters of the known Salmonella Typhimurium-related illnesses from the outbreak involved children younger than 10, and the median age of patients was 4. The age distribution is not typical for Salmonella outbreaks, he said, but the CDC has seen similar distributions in outbreaks associated with pet turtles and baby chicks.
"It was clear early on that there was a large proportion of children affected by this outbreak," Dr. Sodha said. At least six patients have been hospitalized.
In an announcement Dec. 7, the CDC said preliminary analysis suggested contact with pet frogs was likely the source of the S Typhimurium-related illnesses reported between June 24 and Nov. 14. Bacteria matching the outbreak strain were found in aquariums that contained aquatic frogs in three homes of people who became ill.
Julia Hall, foodborne epidemiologist for the Utah Department of Public Health, said at least the first six cases reported in her state by mid-December involved children between 7 months and 11 years of age. Some of the cases have been associated with aquatic animals, and she has worked with the CDC and other states in investigating some animal distributors and vendors as possible sources of the outbreak.
The outbreak was detected through PulseNet, the CDC's national network of public health and food regulatory agency laboratories, Dr. Sodha said. PulseNet identified a cluster of S Typhimurium illnesses with a particular genetic fingerprint, which led to an investiga-tion in collaboration with various states.
The CDC and states are working to determine whether there is a common source for the outbreak and working to understand its scope, Dr. Sodha said.
"This is a new vehicle for an outbreak for us," Dr. Sodha said. "We have not previously had a multistate outbreak related to frogs before, so we're trying to understand better if it's unique to the frogs or is it unique to behaviors associated with managing the frogs or taking care of the frogs that might be causing people to get sick."
The CDC has taken the lead on coordinating with the states, and state agencies are conducting most fieldwork, Dr. Sodha said. He said it is important to educate the public about the Salmonella risk associated with fish and all amphibians, rather than just turtles and reptiles.