As of 25 May 2011, a total of 25 individuals infected with the outbreak strain of S. altona have been reported from 11 states, reports ProMED-mail.

Among the persons with reported dates available, illnesses began between 25 February 2011 and 25 April 2011. Infected individuals range in age from less than one year old to 84 years old and the median age is eight years. Among the 21 patients with available information, eight (38 per cent) were hospitalised. No deaths have been reported.

In interviews, ill persons answered questions about contact with animals and foods consumed during the week before becoming ill. Sixteen (76 percent) of 21 ill persons interviewed reported contact with live poultry (chicks, chickens, ducks, ducklings, geese, and turkeys) prior to becoming ill.

Of ill persons who could recall the type of live poultry with which they had contact, all 16 identified chicks, ducklings or both, and 14 (88 per cent) reported purchasing chicks and ducklings from multiple locations of a nationwide agriculture feed store. Ill persons report purchasing live poultry for either backyard flocks to produce eggs or as pets.

In May 2011, laboratory testing yielded S. altona bacteria from three samples from a chick and its environment collected from an ill person's household in Ohio, and 3 environmental samples collected from chick and duckling displays at two locations of the feed store in North Carolina.

Findings of multiple traceback investigations of live chicks and ducklings from homes of ill persons have identified a single mail-order hatchery as the source of these chicks and ducklings.