They live underwater, eat bloodworms and are promoted on pet websites. But African dwarf frogs can carry salmonella.
An outbreak tied to the frogs sickened nearly 400 people, mostly children, from 2008 to 2011.
Since these miniature amphibians can live up to 18 years, some linked to the outbreak may remain in U.S. home aquariums. That's according to government researchers in a report from the journal Pediatrics.
Five outbreak-linked cases also occurred last year. No one died.
The Centers for Disease Control and Prevention advises washing hands after touching the frogs' aquarium water and says young children should not clean aquariums.
The California breeder linked to the outbreak briefly suspended distribution and cooperated with authorities.