Investigation of foodborne disease outbreaks

Transcription

1 Investigation of foodborne disease outbreaks Wan Chin Chen, M.D. Field Epidemiology Training Program Taiwan Centers for Disease Control Foodborne Infections Network in Taiwan CDC Laboratory diagnosis Surveillance and outbreak detection Outbreak investigation

2 Outlines Principles of foodborne disease outbreak investigation Foodborne disease outbreak detection and management in Taiwan Outbreak investigation of Salmonella Enteritidis infection in Northern Taiwan Foodborne disease outbreaks in USA Foodborne diseases 1 in 6 gets sick each year (48 million illnesses ) 128,000 hospitalizations, and 3,000 deaths Foodborne disease outbreaks in outbreaks reported 14,972 illnesses, 794 hospitalizations, and 23 deaths Median rate: 3.4 (range, ) per 1 million population

3 Why investigate outbreaks? Stop ongoing transmission Facilitate prophylaxis, diagnosis, or treatment Identify risk factors Contribute to the knowledge base Stimulate research Develop sensible prevention strategies Type of foodborne disease outbreaks Localized event outbreaks (or local event) Contaminated commercial product outbreaks (or contaminated product event)

4 Local event Traditional foodborne disease outbreak scenario restaurant, school lunch, summer camp etc. Resulting from an endpoint contamination event (i.e., terminal food-handling error) Affected persons commonly notify public health authorities Inoculum dose and attack rate among exposed persons can be high Solution is typically local education of food workers, changes in individual foodservice policies or operating procedures. Contaminated product event Exposure typically occurs in multiple locations distribution and subsequent handling of the product Victims scattered across different counties, or even countries Low attack rate, resulting in no readily apparent clustering ostensibly sporadic case in the absent of laboratory subtyping Coordinated efforts of a multidisciplinary team for outbreak investigation and control

5 Steps in outbreak investigations Recognition Hypothesis generation Hypothesis testing If successful, identification of the source Investigation of the root cause Short-term interventions Long-term interventions Investigating local event outbreaks Case and control finding Questionnaire development for cohort or case-control study Interviews Analysis Environmental investigation Providing the results

6 Identifying commercial product clusters Usually based on molecular epidemiology subtype matches: pulsed field gel electrophoresis (PFGE) or genotyping Consider background frequency Approaches to PFGE clusters Rule out local events Consider travel (not locally acquired) Assess demographics Assess geography Assess temporality Shotgun Questionnaire Interview or hypothesis-generating interview

7 Foodborne outbreak detection in Taiwan Complaints from the public Report from the hospital* TCDC Hotline 1922 Media report * Foodborne outbreak report or notifiable diseases report (Shigellosis, Typhoid fever, Cholera, Hepatitis A, Hepatitis E, Botulism, Enterohaemorrhagic Escherichia coli etc.) Foodborne outbreak management in Taiwan Local public health bureau Investigation of outbreak and sporadic case of notifiable disease Samples collection Food / environment samples testing CDC Supervise investigation FETP, CDC if indicated Human samples testing Data analysis and exchange with CDC Prevention and control Policy FDA: Food / environment samples testing Data analysis and exchange with CDC Prevention and control Policy

8 PulseNet in Taiwan Established on October 3, : salmonella spp. isolates/ per year Foodborne Questionnaire in Taiwan Adapted from US Shotgun Questionnaire Pilot survey in September 2013 and February 2014 for locally-acquired Hepatitis A cases hundreds of possible food items exposed before illness onset Epi-Info (CDC, Atlanta, GA, USA)

9 2014/05/15 The Call 6 identical isolates of Salmonella Enteritidis detected by PFGE (PFGE SEX.238) Unique PFGE pattern never seen before Isolates received during April 30 May 7 All submitted from Hospital A in Northern Taiwan PFGE SEX.238 Demographics of cluster cases 6 cases in 3 families Household A: 2 Household B: 3 (foodborne outbreak reported ) Household C: 1 Median age: 8 years (range, years) Female/Male: 5/1 No travel history before illness onset All were hospitalized for 6 8 days

10 Outbreak investigation To identify associated food item To identify cause of outbreak Epidemiological investigation Foodborne questionnaire interview Environmental investigation Bakery X, and egg supplier Outbreak-associated cases of S. enteritidis infection in April 2014, according to date of onset (n=8) 6 No. of Cases Foodborne outbreak reported Investigation by local public bureau PFGE SEX.238 cluster identified Probable Confirmed 1 0 4/10 4/12 4/14 4/16 4/18 4/20 4/22 4/24 4/26 4/28 4/30 5/2 5/4 5/6 5/8 5/10 5/12 5/14 Date of Illness Onset

11 Preliminary investigation of Bakery X Conducted by local public health bureau on 4/22 Tiramisu was suspected Bought and eaten by Household B on 4/18 Samples of Tiramisu and liquid eggs were tested Food exposure before illness onset Salmonella cluster cases (n=6) Hepatitis A cases (n=31) Odds ratio 95% Confidence interval Tiramisu Tofu Salad source Fisher s exact test, and 0.5 added for calculation if cell =0 Only Tiramisu was eaten by all 6 cases before their illness, and 5 were from the Bakery X

12 Food samples results Collection Date Specimens Testing Result Sample collected 4/23 Tiramisu E.coli <3.0 MPN/g Bakery X 4/23 Liquid egg 4/29 Liquid egg Salmonella spp. Positive Bakery X S. aureus Negative Bakery X Salmonella spp. Negative Egg supplier S. aureus Negative Egg supplier 23 Environmental investigation of liquid egg supplier 24

13 Cause of outbreak Contaminated liquid egg from surface of shell eggs. No pasteurization of liquid eggs Raw egg yolks in Tiramisu Lessons learned Element for successful source finding Coordination between multidisciplinary team: local public health bureau, FDA, CDC, labs Combing PulseNet and Foodborne Questionnaire might provide aid or hint in contaminated commercial product outbreaks

14 Acknowledgments Epidemiological investigation Dr. Ying Shih Su Dr. Wu Hao Hsin Yi Chen Tsai PulseNet Taiwan Dr. Chien-Shun Chiou Public Health Department, New Taipei City Taiwan Food and Drug Administration Taiwan Centers for Disease Control