King et al., report in Emerging Infectious Disease that on February 11, 2009, two cases of diarrhea were reported to a surveillance coordinator: 1 in a child with HUS and the other in that child’s sibling.

The 2 siblings, 2 and 6 years of age, had diarrhea beginning on February 4 and 5, 2009. Bloody diarrhea developed in the younger child, and HUS was diagnosed on February 9. The older child had non-bloody diarrhea for 3 days and abdominal pain. Questioning of the patients’ parents identified no recent history of travel, contact with farm animals, or outdoor bathing. A food history indicated that the 2 patients had shared an undercooked ground beef burger 4–5 days before symptom onset. The patients’ parents also ate burgers from the same package (box); they did not report any gastrointestinal symptoms.

And they found the same bug in a leftover frozen burger.

STEC serotype O123:H– has been isolated from feces of healthy lambs and sheep in Spain and in southwestern Australia and is considered to be among the predominant ovine STEC serotypes in these countries.

This family outbreak shows that STEC serotype O123:H–, albeit rarely described as causing human illness, can cause severe human infection. This serotype can also cause clusters of STEC infections and be transmitted by ingestion of undercooked ground beef.