Outbreaks of salmonellosis associated with eating uncooked tomatoes: implications for public health. The Investigation Team.

Laboratory-based surveillance of salmonella isolates serotyped at four state health departments (Illinois, Michigan, Minnesota and Wisconsin) led to the identification of multistate outbreaks of salmonella infections during 1990 (176 cases of S. javiana) and 1993 (100 cases of S. montevideo). Community-based case-control studies and product traceback implicated consumption of tomatoes from a single South Carolina tomato packer (Packer A) MOR 16.0; 95% CI2.1, 120.6; P < 0.0001 in 1990 and again in 1993 (MOR 5.7; 95 % CI 1.5, 21.9; P = 0.01) as the likely vehicle. Contamination likely occurred at the packing shed, where field grown tomatoes were dumped into a common water bath. These outbreaks represent part of a growing trend of large geographically dispersed outbreaks caused by sporadic or low-level contamination of widely distributed food items. Controlling contamination of agricultural commodities that are also ready-to-eat foods, particularly fruits and vegetables, presents a major challenge to industry, regulators and public health officials.

Evaluation of an outbreak of foodborne illness initiated in the emergency department.

STUDY OBJECTIVES: For many foodborne outbreaks, the pathogen and food vehicle never are identified. Delayed collection of epidemiologic and microbiologic information may contribute to this. We postulated that collection of this information from ill persons as they presented to the emergency department during a recent outbreak might contribute to earlier identification of the pathogen and vehicle. DESIGN: At least 690 of 1,900 conventioneers developed gastrointestinal symptoms after attending a banquet. A questionnaire was developed to collect information on specific food histories, incubation periods, symptoms, physical findings, and demographics. These results were compared with results of investigations by the city and state departments of public health. SETTING: The ED of Rush-Presbyterian-St Luke's Medical Center, a tertiary care university hospital in Chicago, Illinois. TYPE OF PARTICIPANTS: Adults (24 men and nine women) presenting to the ED with gastrointestinal symptoms after eating a common meal. MEASUREMENTS AND MAIN RESULTS: The clinical syndrome suggested an invasive pathogen. Based on this, clinical microbiology laboratory procedures were modified (isolation plates were reviewed during the evening shift). This led to early identification of the first isolates (Salmonella enteritidis) from the outbreak. The questionnaire also narrowed the vehicle to one of two foods served. Investigations by the departments of public health subsequently identified one of these, bread pudding with a raw egg based-sauce, as the vehicle. CONCLUSION: Outbreak evaluations can begin in the ED or any other patient care facility. This evaluation need not always add significantly to the expenditure of time, manpower, or laboratory studies. The evaluation of even a small percentage of ill persons from a large outbreak may provide useful epidemiologic information and be particularly important in settings with limited public health resources.

Outbreak of leptospirosis associated with swimming.

Between July 7 and 18, 1991, five boys from a small town in rural Illinois experienced the onset of an acute febrile illness subsequently confirmed as leptospirosis by serologic tests. A cohort study found that swimming in a small swimming hole, Steel Tunnel Pond, was associated with disease (P < 0.01), the attack rate being 28%. Leptospira interrogans serovar grippotyphosa was isolated from urine cultures from two of the case patients and from a culture of Steel Tunnel Pond water. A high seroprevalence for grippotyphosa was found in animals near the pond. Drought conditions had been present in the month before the outbreak, creating an environment in the pond which probably facilitated transmission of the organism from area animals to humans. Although leptospirosis is infrequently reported in humans in the United States, it is endemic in animals and the potential for outbreaks exists, especially when environmental conditions are favorable.

Massive outbreak of antimicrobial-resistant salmonellosis traced to pasteurized milk.

Two waves of antimicrobial-resistant Salmonella typhimurium infections in Illinois totaling over 16 000 culture-confirmed cases were traced to two brands of pasteurized 2% milk produced by a single dairy plant. Salmonellosis was associated with taking antimicrobials before onset of illness. Two surveys to determine the number of persons who were actually affected yielded estimates of 168 791 and 197 581 persons, making this the largest outbreak of salmonellosis ever identified in the United States. The epidemic strain was easily identified because it had a rare antimicrobial resistance pattern and a highly unusual plasmid profile; study of stored isolates showed it had caused clusters of salmonellosis during the previous ten months that may have been related to the same plant, suggesting that the strain had persisted in the plant and repeatedly contaminated milk after pasteurization.

Occurrence of La Crosse (California serogroup) encephalitis viral infections in Illinois.

La Crosse (LAC) virus (California encephalitis serogroup) was identified as the etiologic agent of disease in 61 cases of California encephalitis (CE) that occurred in Illinois between 1976 and 1980. This group represented 54% of all 114 laboratory-diagnosed cases of CE between 1966 and 1980. Key epidemiologic observations included: 88% of the 61 cases had onset in July, August, or September; the 5- to 9-year-old age group represented 48% of the cases; the male:female sex ratio was 2:1; 97% of the cases occurred in the northern half of the state; and 61% of the cases occurred in Peoria County. Four instances of probable common source of exposure were reported. Average length of hospitalization was 8.3 days (range 3-31 days). Hospitalization costs were estimated at $3,967-$5,750 per case. An "average" year in Illinois yields 12 cases of LAC encephalitis with direct hospitalization costs of $47,604-$69,000.

Postexposure trial of a human diploid cell strain rabies vaccine.

A human diploid cell strain vaccine (HDCV) was evaluated in 90 persons treated after exposure to rabies, 21 of whom were bitten by proven rabid animals. Intramuscular doses of HDCV were given on days 0, 3, 7, 14, and 28, and human rabies immune globulin (HRIG) was given on day 0. Antibody to rabies virus was tested for by the rapid fluorescent focus inhibition test; adverse reactions were assessed from physician's forms. All 87 persons tested developed titers of greater than or equal to 0.5 international units (IU)/ml, with a maximum geometric mean titer of 15.0 IU/ml on day 42. One year after vaccination, all 33 persons tested had antibody to rabies virus. After one or more doses of vaccine, mild local or systemic reactions were reported in 19.0% and 21.4% of persons, respectively. No serious reactions occurred. The results show that this HDCV (plus HRIG) was safe and effective in eliciting antibody in postexposure prophylaxis of rabies. When it becomes available, it is recommended over the present treatment regimen.