According to a posting on ProMED Mail cases of listeriosis were attributed to consuming prepared meals produced by Yu Shang Food, Inc. Of 11 diagnosed cases nine required hospitalization. One case involved a pregnant woman and her twins both of whom dyed. Cases were reported in California, Illinois, New Jersey and New York. As with many foodborne outbreaks, the actual number of those infected is higher than the confirmed cases. Traceback and identification of the source of Listeria infection is complicated by the prolonged incubation period that may extend to 70 days.
Pregnant women and their infants, the immunosuppressed and elderly are more susceptible to listeriosis than healthy individuals. In this outbreak, the age of patients ranged from less than one year of age to 86 years. All cases were of Asian ethnicity consistent with the products distributed by Yu Shang Foods. The vehicle of infection was confirmed to be ready-to-eat chicken products. Investigations showed that processed pork snouts were contaminated with Listeria suggesting the presence of the pathogen in the environment and equipment of the plant of origin.
On November 9th, Yu Shang Food recalled ready-to-eat meat and poultry products with a further expansion to a total recall in late November.