Salmonella Enteritidis Outbreak Associated with a Wedding Event Cleveland, OH September 2, 2011 to September 17, Final Report December 29, 2011

Transcription

1 Salmonella Enteritidis Outbreak Associated with a Wedding Event Cleveland, OH September 2, 2011 to September 17, 2011 Final Report December 29, 2011 Cleveland Department of Public Health Office of Communicable Disease Surveillance and Epidemiology 75 Erieview Plaza Cleveland, OH EPIS (3747) 1

2 INTRODUCTION On Monday, September 12, 2011, the Cleveland Department of Public Health (CDPH), Office of Communicable Disease Surveillance and Epidemiology (OCDSE) received a call from the Cuyahoga County Board of Health (CCBH) that a patient who resided in their jurisdiction tested positive for Salmonellosis. It was notified to the CDPH that the patient attended a wedding on September 2, 2011, where there were six other individuals whom the patient indicated became ill after attending the same wedding. Contact information was available for 217 participants and employees that attended the wedding. Questionnaires were administered which contained information on demographics, symptoms and exposure histories. A total of 104 participants of which 37 people reported symptoms consistent with gastrointestinal (GI) illness and 67 reported no symptoms after attending the wedding event. The wedding was held in a banquet hall of a restaurant. The catering for the wedding was also provided by the restaurant. The restaurant was located in the Cleveland, Ohio jurisdiction. The OCDSE contacted the bride for a list of all participants that attended the wedding on September 2, The catering company was also contacted to obtain a menu and a list of employees that worked at the event on September 2, A food service inspection was conducted at the restaurant where the wedding event was held on September 15, 2011 by the environmental department staff and an epidemiologist. The CDPH collected a total of 8 stool samples for laboratory testing. BACKGROUND Salmonellosis is an infection with a bacterium called Salmonella. Most persons infected with Salmonella develop diarrhea, fever and abdominal cramps hours after infection. The illness usually lasts 4-7 days, and most persons recover without treatment; however, in some persons the diarrhea may be so severe that the patient needs to be hospitalized. Salmonella live in the intestinal tracts of humans and other animals, including birds. Salmonella are usually transmitted to humans by eating foods contaminated with animal feces. Contaminated foods usually look and smell normal. Contaminated foods are often of animal origin, such as beef, poultry, milk or eggs, but any food, including vegetables, may become contaminated. Food may also become contaminated by the unwashed hands of an infected food handler who forgot to wash his or her hands with soap after using the bathroom 1. Every year, approximately 40,000 cases of Salmonellosis are reported in the United States. Because many milder cases are not diagnosed or reported, the actual number of infections may be 30 or more times greater. Salmonellosis is more common in the summer than in the winter. Children are the most likely to get Salmonellosis. Young children, the elderly and immunocompromised individuals are the most likely to have severe infections. It is estimated that approximately 400 persons die each year with acute Salmonellosis. In Ohio, there is a slight increase in incidence during the midsummer. Most recognized cases occur in children <5 years of age, adults years of age and adults >60 years of age 1. In the past 5 years, four foodborne outbreaks of Salmonella infections occurred in Cleveland, Ohio as well as sporadic cases. Since January 1, 2011, there have been 46 cases of Salmonella infection reported in Cleveland, Ohio, a rate of 11.6 cases per 100,000 persons. 2

3 METHODOLOGY Surveillance Case Finding and Assessment A list of 205 attendees (including names and phone numbers) of the wedding event on September 2, 2011 was obtained. Additionally, a complete list of 12 food service workers who worked on September 2, 2011 was obtained from the restaurant. The line lists were characterized to indicate the attendees and workers who were ill versus those who were not ill. Interagency Notification All appropriate city, state, and federal agencies were immediately notified by and/or phone upon receiving information about the outbreak of GI illness associated with the wedding event. These agencies included the CDPH internal staff (Health and Environmental divisions), The Ohio Department of Health (ODH), the CCBH, and the Centers for Disease Control and Prevention (CDC). Case Definition For the purpose of this study, a case was defined as an employee or attendee of the wedding event with onset of GI illness after September 2, Epidemiological Investigation Epidemic Curve An epidemic curve was developed to determine the magnitude and incubation periods associated with the outbreak from the time period of September 2, 2011 to September 17, Survey Administration An outbreak specific questionnaire was developed to interview all attendees and employees who were present at the wedding event to identify potential sources of exposure (e.g. food histories) and to characterize the type of illness reported. A total of 104 interviews were conducted from the 217 attendees and employees that information was available for. Descriptive Statistics Descriptive statistics for age, gender, race, ethnicity, symptoms, hospitalizations, and food specific attack rates were calculated for study participants to assist in formulating hypotheses about potential sources of the outbreak. Study Design A retrospective cohort study was conducted to assess the outbreak. The Risk Ratio (RR) measure of association was used to quantify the strength of relationship between exposures and illness outcomes. Additionally, Confidence Intervals (CI) and p-values with accompanying Chi-square ( ) test statistics were calculated to test the reliability of the measure of association. Performing the aforementioned analyses assisted in determining which exposures were significant risk factors for illness outcomes. 3

4 Hypotheses There was one hypothesis developed as a result of the preliminary meeting, inspection of the facility and background of the outbreak. The following hypothesis was derived from epidemiological data collection: Ho: There is no significant association between food items served and GI illness. Ha: There is a significant association between food items served and GI illness. Laboratory Investigation Viral and Bacterial Testing of Human Subjects Individuals that were classified as a case were offered the opportunity for stool culture testing. No stool specimen was available for testing at the time of interviewing for ill attendees of the wedding. Individuals that submitted a stool sample to their doctor s office were reported to the local and county health jurisdiction in which the patient resided if the results were positive. CDPH collected stool specimens for eight employees regardless of whether or not they were symptomatic. This testing was conducted to ensure that no food handlers were ill, which could have contributed to food contamination. The stool specimens were shipped to the ODH laboratory for testing. All employees were tested for Salmonella and Campylobacter, of which, all tested negative. ODH further determined that Salmonella Enteritidis was the serotype associated with the outbreak. No other tests were indicated since Salmonella Enteritidis had already been serotyped with ill attendees that tested positive after attending the wedding. One attendee tested positive for both Salmonella Enteritidis and Campylobacter after attending the wedding. Food samples were not available for laboratory testing. Environmental Investigation A CDPH Registered Sanitarian did an inspection of the food operations at the restaurant that provided the food for the wedding reception. There were several areas of the food operation process assessed by the Registered Sanitarians which included limitation of growth of organisms, protection from contamination, maintenance and operation, and protection of clean items. A CDPH Epidemiologist performed an environmental investigation to assess hand washing protocols, ill food handler exclusion policies, and cleaning protocols. The manager and employees were educated on controlling person-to-person transmission of bacteria and viruses. Additionally, the facility was provided with hand washing posters. Furthermore, the facilities received fact sheets on hand washing protocols, EPA approved sanitizers, and universal infection control recommendations. RESULTS Surveillance Case Finding and Assessment Upon examination of the line list developed for ill and well event attendees and employees, 37 (17%) out of the 217 were identified to be ill. Among those identified to be ill, none were employees. 4

5 Case Count Epidemiological Investigation Epidemic Curve The epidemic curve (Figure 1) was identified as a common source curve. A common source epidemic curve is indicative of an outbreak that has occurred as a result of continuous exposure to a harmful source (period of exposure may be brief or long). In the case of this outbreak, food was determined to be the potential harmful source. The outbreak peaked on September 4, 2011 with a total of 7 cases reporting onset of symptoms. As also seen by the epidemic curve, the symptoms continued to occur throughout the next two weeks and peaked again on September 8, 2011 with 5 cases reporting onset of symptoms. The last day of onset of symptoms being reported was September 17, 2011 from the 104 event attendees that were interviewed. The median incubation period was 48 hours. On average the incubation period for Salmonella is hours, but can range anywhere from 6-72 hours. Nine cases (24%) were laboratory confirmed and 28 (76%) cases were non-laboratory confirmed. Approximately, 43% (16 cases) of the cases had onset of symptoms within 72 hours and 57% (21 cases) had onset of symptoms thereafter. The cases with onset of symptoms after 72 hours may have represented cases with longer incubation periods than normal. Two cases (5%) were determined to be outliers who had onset of symptoms exceeding 3 times the normal incubation period. These cases may have represented secondary cases (person-to-person transmission) that contracted the illness from an individual who was exposed to the original harmful source Common Source Epidemic Curve Salmonella Enteritidis Outbreak Associated with a Wedding Event September 2, 2011 to September 17, 2011 Laboratory Confirmed Non-Laboratory Confirmed Date of Illness Onset Figure 1: Epidemic curve for Salmonella Enteritidis Outbreak Associated with a Wedding Event, Sept ,

6 Survey Administration A total of 217 participants were at risk who attended the wedding event including employees and attendees. CDPH and CCBH were able to conduct 104 interviews (response rate = 48%). Of the 104 interviews conducted, 37 (36%) met the case definition and 67 (64%) individuals did not meet the case definition. Descriptive Statistics The demographic characteristics of the cases were comprised of the wedding attendees only, since no employees that worked at the event reported to be ill. There were 37 ill attendees that were analyzed. The average age was 38 years, the minimum age was 9 years, and the maximum age was 74 years. Those attendees that were between the ages of represented the largest number of cases, 54%. Nearly 90% of the attendees were White and over 50% of the attendees were female (Table 1). Table 1: Demographic characteristics of cases. Gender Characteristic n=37 1 Value Male 17 46% Female 20 54% Age (years) % % % % % % Age (general statistics in years) Mean Minimum -- 9 Maximum Median Mode

7 Characteristic n=37 1 Value Race White 33 89% Black/African-American Asian American Indian/Alaskan Native Native Hawaiian/Other Pacific Islander Other 4 11% Ethnicity Hispanic Non-Hispanic % 1 The number of cases may be different for each characteristic due to missing values. The cases presented with a number of GI signs and symptoms after attending the wedding on September 2, These symptoms included diarrhea, vomiting, abdominal cramps, nausea, body aches, joint pain, fatigue, chills, and fever. The most common symptoms reported were diarrhea (95%), and stomach cramps (87%) (Table 2). The case definition determined the true number of cases represented in the outbreak. The average duration of symptoms was 7 days. The minimum duration of symptoms was 1 day and the mode (most frequently reported) of duration of symptoms was 7 days. Eight percent of the cases reported being hospitalized. The statistics on symptom durations helped to determine plausible causative agents associated with the outbreak. Hypotheses All of the food items consumed at the wedding reception dinner were analyzed for statistical significance based upon questionnaire responses. It was concluded that multiple food items were significantly associated with illness (Table 3). The food items that were significantly associated with illness were the sausage (exposed attack rate: 72%), classic tossed salad with cheese (exposed attack rate: 67%), and pizza (exposed attack rate: 46%). Additionally, those that consumed the salad with cheese (RR=1.926) were nearly 2 times more likely to develop illness than those that did not consume it. Furthermore, those that consumed the sausage (RR=2.433) and pizza (RR=2.686) were nearly 3 times more likely to develop illness than those that did not consume those food items. Other food items such as, bruschetta (exposed attack rate: 54%), and veal marsala (exposed attack rate: 86%) were moderately associated with illness. Based on the analysis of the food items implicated to have significantly contributed to the illness associated with this outbreak; it was theorized that the sausage, salad with cheese, and the pizza could have been contaminated sometime during the preparation cycle. 7

8 Table 2: Symptom history characteristics of cases. Characteristic n=37 1 Value Symptom Frequency Stomach cramps 32 87% Diarrhea 35 95% Bloody Diarrhea 6 16% Vomiting 7 19% Headache 24 65% Body Aches 18 49% Joint Pain 11 30% Fatigue 22 60% Chills 22 60% Duration of Symptoms (days) Mean -- 7 Minimum -- 1 Maximum Median -- 7 Mode -- 7 Hospitalized Yes 3 8% No 34 92% 1 The number of cases may be different for each characteristic due to missing values. 8

9 Table 3: Associations with illness by specific wedding event food items. Exposure Item Exposed Unexposed Statistical Tests Lower Upper Ill Well Total AR Ill Well Total AR RR x 2 P-Value 95% C.I. 95% C.I. Bruschetta % % Classic Tossed Salad With Cheese % % With Dressing % % Bread With Butter % % Sausage % % Pizza % % Roasted Potatoes % % Green Beans % % Chicken Picatta % % Veal Marsala % % Eggplant Marinara % % Pasta Marinara % % Cake % % Cupcakes % % Laboratory Investigation Viral and Bacterial testing of Human Subjects Salmonella was isolated from the individuals that submitted a stool sample at their doctor s offices. Specifically, ODH serotyped the Salmonella as the Salmonella Enteritidis strain. The samples were detected positive from event attendees only and one event attendee also tested positive for both Salmonella and Campylobacteriosis. Eight employees that were required to submit a stool sample to ODH tested negative for the two tests that were isolated for Salmonella and Campylobacteriosis. Environmental Investigation The environmental inspection report revealed multiple violations which included correction in packaged and unpackaged ready-to-eat foods, improper date markings on ready-to-eat and refrigerated foods, cross-contamination of food and surfaces such as cutting blocks and boards. Additional violations included inadequate control of insects, rodents, and other pests, and protection from contamination by failing to change gloves for more than one task during food preparation. Please see additional information on violations in the environmental inspection report attached (Appendix A). 9

10 LIMITATIONS & LESSONS LEARNED There were three primary limitations considered with respect to the study outcomes including loss to follow-up, recall bias, and sample testing. Loss to follow-up for some participants may have distorted findings due to some participants not being available for questioning, thereby resulting in a loss of information and a reduced sample size (response rate = 48%). Findings may have also been distorted from recall bias. Although interviewers were instructed to prompt respondents to try to recall with precision, some participants ability to provide specific answers to items may have been impacted by the time delay between the wedding event taking place and the initiation of the interviewing process. Due to the inability to test food items for bacterial pathogens, there was no laboratory evidence to definitively support which food items may have been contaminated with Salmonella. Additionally, food trace back capabilities were inhibited due to the lack of food sample testing. There were several lessons learned from the investigation that will help guide and inform future investigation protocols which include communication, isolation and sample testing, education and inspection. Communication will need to be kept open between the facility implicated and the CDPH in order to ensure that outbreak investigation protocols are complied with as needed. Isolation and sample collection requirements for food handlers will need to be strictly enforced via management to ensure citizen safety. CDPH will need to consider conducting an in-service with facility workers in order to ensure hand washing and food safety practices are provided to the facility within a timely manner. CDPH will also need to consider conducting environmental health inspections within 24 hours for specific agents, where applicable. DISCUSSION Overall, this outbreak was characterized by diarrhea and stomach cramps of attendees at a wedding event. The agent determined as the cause of the outbreak was Salmonella and serotyped as Salmonella Enteritidis. One wedding attendee tested positive for Salmonella and Campylobacteriosis. Campylobacteriosis is a bacterial infection, transmitted in similar ways as Salmonella. Investigation of the outbreak began when the CDPH was notified on September 12, 2011 about a case that tested positive for Salmonella and knew of others that were ill after attending a wedding event on September 2, The outbreak peaked on September 4, As a result of this investigation it was concluded that food items significantly associated with illness were the sausage, pizza, and salad with cheese. Food items moderately associated with illness were the veal marsala and bruschetta. The food items that were significantly associated with illness could have resulted from cross-contamination and mishandling of food during the preparation cycle. Upon investigation of the restaurant, many violations were noted in relation to the food preparation process including mishandling of food and utensils used to prepare the meals. Leaking raw animal foods were stored above ready-to-eat foods which could have provided as a source of cross-contamination. Additionally, cross-contamination could have occurred when ready-to-eat foods were not separated from raw animal foods during preparation. Furthermore, foods that were unwrapped or in uncovered containers could also have been a source of cross-contamination. Salmonella is a bacterial infection that causes diarrhea, vomiting, fever, and abdominal cramps hours after infection. The illness typically lasts 4-7 days where most persons recover without treatment. Salmonella Enteritidis is one of the most common serotypes of Salmonella bacteria reported worldwide 2. Eggs have been the most common food source linked to Salmonella Enteritidis infections. Salmonella Enteritidis infections can be present in hens and an 10

11 infected hen can lay many normal eggs while occasionally laying eggs contaminated with Salmonella Enteritidis infection 2. Other sources such as raw milk, pork, beef, sprouts and raw almonds have also been identified to be associated with Salmonella Enteritidis 2. Cross-contamination in the kitchen with unwashed hands or food preparation surfaces can also transfer Salmonella Enteritidis from foods of animal origin to other foods. Large amounts of leftover food or unused food that is not properly refrigerated can also grow the bacteria. According to CDC, Salmonella was the second most commonly reported etiologic agent for 2008, causing 110 (23%) confirmed outbreaks in the United States. Among the 108 Salmonella outbreaks during 2008, Enteritidis (serotype consistent with this outbreak) was the most common serotype, causing 29 (27%) confirmed outbreaks. Salmonella is the leading cause of hospitalizations and deaths among outbreaks caused by foodborne bacteria and the cause of more than half of the multistate outbreaks (i.e. outbreaks in which the exposure occurred in more than one state) 3. Recent Food and Drug Administration safety initiatives to improve the safety of shell eggs have been regulated as of Additional steps to identify infected hens in flocks that supply eggs and increasing quality assurance and sanitation measures have also taken place. Lastly, rules to include refrigeration during storage and transportation have been placed. RECOMMENDATIONS Important recommendations to prevent transmission of Salmonella and particularly serotype Salmonella Enteritidis include, avoiding raw or undercooked eggs, poultry, or other meats. Persons should not consume raw or unpasteurized milk or other dairy products. Cross-contamination of foods should be avoided and uncooked meats should be kept separate from produce, cooked foods, and ready-to-eat foods. Additional recommendations include the following: 1). Frequent and thorough hand washing for at least 20 seconds with warm water and soap before and after handling food, using the bathroom, and coming into contact with animals. 2). Washing cutting boards, dishes, utensils, and counter tops with warm soap and water after contact with raw eggs or raw chicken. 3). Refrigerate leftover or unused foods promptly. 4). Avoid eating dishes with raw or lightly cooked eggs. 11

12 SPECIFIC RECOMMENDATIONS FOR RESTAURANT ESTABLISHMENT SALMONELLA ENTERITIDIS OUTBREAK Isolation/Restriction: o Increase surveillance of staff and restrict ill employees from the restaurant until stool samples tested negative for Salmonella and Campylobacteriosis. o Symptomatic staff members should not return to work until diarrhea has ceased and two additional stool samples tested negative 1. o Report daily any additional ill employees/attendees to CDPH for follow up. Cleaning/Disinfection: o The restaurant was given guidelines on environmental cleaning and disinfection, and an environmental check list was also discussed. o Comply with cleanliness, hand washing, and food guidelines from the Division of Environment. Information: o The restaurant was given guidelines on controlling person-to-person transmission of viruses and bacteria, Salmonella fact sheet, and hand washing fact sheet. o Post Hand Washing and Cover your Cough signs in employee/public bathrooms and general areas (signs were provided by CDPH). o Provided in-service and education/prevention materials to all employees on the outbreak on September 15,

13 REFERENCES 1. ODH- Infectious Disease Control Manual- Salmonellosis. Ohio Department of Health. Web. 4 November CDC- Salmonella Serotype Enteritidis- General Information. Centers for Disease Control and Prevention. Web. 4 November CDC- MMWR- Surveillance for Foodborne Disease Outbreaks United States, Web. 4 November

14 Appendix A 14

15 15

16 16

17 17

18 18

19 19

20 20