Salmonella Heidelberg infections were spread over 13 states and linked to Foster Farms chicken with illness dates from 4 June 2012 to 16 April 2013.
It was initially discovered by the Oregon Health Authority and the Washington State Department of Health and the pulsed-field gel electrophoresis (PFGE) pattern was the same which was linked to chicken from Foster Farms in 2004 by the Washington State Department of Health.
Median patient age of the latest outbreak was 22 years (range: <1 to 94 years) and 73 (55%) of 132 patients with data available were female.
Thirty-three (31%) of 105 patients with known outcomes were hospitalized; no deaths were reported.
Of 70 patients who responded to a survey, 55 (79%) reported consuming chicken in the week before illness onset.
The majority of cases were reported from four states in the Pacific Northwest: Washington, 57 cases; Oregon, 40; Alaska, 13; and California, 11.
However, the CDC said the outbreak appears to have ended, based on the calculated five year baseline of the expected number of cases reported per week.
PulseNet data collected before the outbreak shows that four to eight human isolates of this Heidelberg pattern typically are uploaded each month from June to November but during this outbreak, an average of 12 human isolates matching the outbreak strain was uploaded each month.
Four unopened chicken samples from three Washington patients' homes were tested for Salmonella; all yielded the outbreak strain and were traced back to two Foster Farms slaughter establishments.
Three were susceptible to all antimicrobials tested; one was resistant to gentamicin, streptomycin, and sulfisoxazole.
USDA-FSIS also sent an incident investigation team to one Foster Farms slaughter establishment; the results of that investigation have not yet been finalized.