During 2003, 576 culture-confirmed cases of Salmonella infection (11.7 per 100,000 population) were reported. This represents a 3% decrease from the 593 cases reported in 2002 and a 8% decrease from the median annual number of cases reported from 1996 to 2002 (median, 626 cases; range, 593 to 693) (Figure 1). Four serotypes, S. Typhimurium (124 cases), S. Enteritidis (107 cases), S. Heidelberg (63 cases), and S. Newport (41 cases), accounted for 58% of cases reported in 2003. There were three cases of S. Typhi infection, but only two had symptoms compatible with typhoid fever. Six percent of salmonellosis case-patients were less than 1 year of age, and 25% were less than 8 years of age. Twenty-four percent of case patients were hospitalized for their infection. Of 538 cases who were interviewed, 68 (13%) traveled internationally during the week prior to their illness onset.
Two case-patients died. Isolates from these case-patients included one S. Berta isolated from stool and one S. Typhimurium isolated from blood. Both had serious underlying medical conditions (hepatocelullar carcinoma, history of kidney transplant).
Six outbreaks and one probable outbreak of salmonellosis were identified in 2003. One outbreak involved contact with reptiles. The remaining five outbreaks and the probable outbreak were food-borne.
One outbreak of S. Ealing as a result of indirect contact with reptiles was identified. This outbreak resulted in two culture-confirmed cases among visitors to a private residence where more than 30 reptiles were housed. The case patients visited the house in February and April. Numerous reptile samples and environmental samples from the human living areas, including the kitchen sink, tested positive for several Salmonella serotypes, including the outbreak strain of S. Ealing.
The first food-borne outbreak of 2003 occurred in April. Several families purchased a cow, killed it, and butchered it at the farm where it was purchased. The beef was subsequently eaten at various locations. Salmonella Somatic Group D (9,12: non-motile) was isolated from the stool of three persons, and S. Enteritidis (motile) was isolated from the stool of one person. These four Salmonella isolates were indistinguishable by PFGE subtyping. Campylobacter jejuni was isolated from the stool of two cases, including one case-patient co-infected with Salmonella. One case-patient tested positive for Aeromonas hydrophilia. Eleven additional cases of illness were identified but were not culture-confirmed.
A probable outbreak of S. Litchfield associated with a restaurant occurred in April. Two patrons became ill with salmonellosis after eating at the same restaurant over a 2-day period. No additional cases were identified. The source and vehicle of transmission were not confirmed.
A cluster of six S. Enteritidis cases with illness onset dates ranging from May 13 to June 22 was identified in June. The outbreak was associated with eating at one restaurant. Eggs from a producer in Iowa were most likely the initial vehicle in the restaurant outbreak. One additional case-patient also ate eggs at a different restaurant.
In September, three persons became ill with S. Saint Paul after attending a block party. Two additional cases of gastrointestinal illness were identified but were not tested for Salmonella. Toffee bars were statistically associated with illness, but because there was some cooking of foods of animal origin going on during the event (e.g., grilling chicken), cross-contamination of surfaces or ready-to-eat food items was a possible cause of this outbreak.
A S. Heidelberg outbreak associated with eating at a restaurant resulted in 41 culture-confirmed S. Heidelberg cases among patrons and employees in September, including a resident from Wisconsin and one from Washington. An additional 16 unconfirmed cases were identified. Consumption of eggs and pancakes was associated with illness. Multiple violations in food holding, handwashing, disinfection, and labeling of food items were identified.
In November, a S. Enteritidis outbreak associated with eating at a restaurant resulted in 20 patrons and seven restaurant employees with confirmed S. Enteritidis infections. Three additional ill patrons were identified but not confirmed. Shell eggs were confirmed as the ultimate source of S. Enteritidis through trace back and environmental testing at the farm of origin. Deficiencies in food holding and preparation, including inadequate refrigeration and potential cross-contamination, were identified at the restaurant. Deficiencies were also identified at the distributor that supplied shell eggs served at the restaurant. Extensive S. Enteritidis contamination was found at the source egg farm. A later sporadic S. Enteritidis case was associated with eggs from the implicated farm, but not the restaurant. Eggs from this farm were diverted to pasteurization until FDA testing criteria were met.
Note: For up to date information on Salmonellosis see Salmonellosis (Salmonella)
Go to full issue: DCN, August 2004: Volume 32, Number 4