Our vision: Healthier communities, Excellence in healthcare Our values: Teamwork, Honesty, Respect, Ethical, Excellence, Caring, Commitment, Courage Designing and conducting a model investigation of foodborne disease Prepared by Dr Craig Dalton Public Health Physician For Viet Nam Food Authority 8 th June 09
2 Outline What does “the model” outbreak investigation look like How does the model outbreak support a model food safety system What are the key needs to achieve the model foodborne outbreak system
3 Start with a story….. Outbreak investigation is important because: –Helps control current outbreak –Helps us learn how to prevent future outbreaks
In 1993, as a trainee foodborne disease epidemiologist, I realised that my 9 year old niece knew more about the epidemiology of Salmonella in the USA than I knew about Salmonella in Australia! I was trying to stop her brother putting this frog in his baby sisters mouth because it might cause salmonellosis. She said: Uncle Craig,don’t worry about frogs - eggs are the main cause of Salmonella!
5 What makes a 9 year old so smart? Good outbreak investigations National database of foodborne outbreaks Good communication of problem: –Foods –Food preparation errors –Settings
Salmonella outbreaks, USA, 1992 80 Salmonella outbreaks 60 outbreaks due to S. Enteritidis Eggs implicated in 22/25 (88%) with known food Deaths in nursing homes Recommendation: pasteurised eggs
What is the commonest cause of salmonellosis in Australia? Questions we couldn’t answer…
What is the major food handling error responsible for foodborne disease in Australia ? ? Lack of handwashing ? Temperature abuse
We needed a national outbreak database Outbreak report No. ill:35 Bug: S. agona Association:Relative risk of 9 Vehicle: Egg rolls Contributing factors: Temp abuse Setting: Restaurant Outbreak report No. ill: 35 Bug: S. agona Association:RR of 9 Vehicle: Egg rolls Cont factors: Temp abuse Setting: Restaurant
10 Every outbreak is a lesson in prevention A national database of foodborne outbreak data is a database of “lessons” in prevention. Need good outbreak investigations to capture these lessons – expert teams that mentor Standardised methods of investigation and documenting the outbreaks. –Manuals that help standardise practice –Standard case definitions, questionnaires –Standard data entry forms for national database –Can be online
12 Training and practice in model outbreak investigation methods Standard Outbreak Reports Pathogen Place Food Hygiene practices
13 Standardising questionnaires NetEpi – web based questionnaires Used in large distributed outbreaks
14 Using Outbreak Summary Data Summary data can inform policy work by other agencies Summarise by commodity or by aetiology Important to feed back to regulation/intervention – complex web of food production and food safety Broader attribution efforts
Benefits HACCP food safety programs based on causes of foodborne disease in your own jurisdiction Prioritise food safety policy based on true morbidity and mortality NOT media or local folklore Assess effectiveness of prevention programs
17 Steps of an outbreak investigation Establish the existence of an outbreak Verify the diagnosis Defining and counting cases Determining the population at risk Descriptive epidemiology Developing hypotheses Evaluating hypotheses Additional epidemiological, environmental and laboratory studies Implement control and prevention measures Communicate findings
18 Establish existence of an outbreak Definition: a) The observed number of cases of a particular disease exceeds the expected number. b) The occurrence of two or more cases of a similar foodborne disease resulting from the ingestion of a common food.
19 Verifying the diagnosis Diagnosis may be –Syndromic e.g. vomiting and diarrhoea –Laboratory Laboratory diagnosis helps ensure we are comparing “apples with apples” rather than parasitic diseases with bacterial diseases.
20 Defining and counting cases Case definition –Time, person, place Case definition for salmonella outbreak –Suspect : All persons with diarrhoea (3 or more loose stools) and abdominal cramps within one week of attending the feast. –Confirmed case: suspect case with salmonella of same serotype isolated from stool. Depending on local epidemiology of salmonellosis we may need salmonella serotyped or further subtyped to ensure were are comparing “apples with apples”)
21 Gastroenteritis after an awards ceremony Approximately 3000 attendees Awards for State Emergency Services for Thredbo landslide disaster response Reports from Hunter SES of diarrhoea 19 hours post lunch »Outbreak reported 3 days after luncheon
22 Established outbreak & case finding Multiple bus loads of Emergency Volunteers returned all over the state Obtained a list of volunteer groups and contacted them asking about symptoms Kept a team of 8 people back to 11pm calling organisers, tracking down and interview cases and well people. Many reported diarrhoea, no other common link apart from the awards luncheon.
23 Verifying diagnosis No specimens available at time of report Clinical case definition: –Attended luncheon at Governors mansion –Onset of diarrhoea* within 3 days of luncheon Collected specimens –Drove to cases houses –Left stool collection kit –Paged us when stool sample ready for pick up
24 Remove barriers to specimen collection call twice daily to check give written advice on how to collect stool specimens provide containers, refrigeration block. pick up from patients home run a clinic consider rectal swabs
25 Descriptive epidemiology 171 persons met the case definition –defined as eating at the luncheon and reporting diarrhoea that lasted more than 9 hours or diarrhoea that was accompanied by abdominal cramps or vomiting in the 3 days after attending luncheon. Median incubation period 9 hours –(range, 9 to 48 hours) Median duration of illness was 24 hours (range, 1 to 96 hours).
26 Descriptive epi - Symptoms Diarrhoea 100% Abdominal cramps 72% Nausea 30% Vomiting 15% Fever 5% So what pathogen is this symptom profile and incubation period consistent with?
27 Environmental investigation Catered function prepared off site It was the largest function ever catered by this caterer (3,000 people) Cooked foods days ahead Ran out of cool room space Food for lunch delivered into tents from 4am in the morning and stored under tables and consumed from 1pm to 4pm (up 12 hours after delivery!) No food for testing
28 Food specific attack rates – Awards Ceremony Persons ate specified food Persons did not eat specified foods FoodIll/TotalAttack rate (%) Ill/TotalAttack rate (%) Relative Risk 95% CI Chicken116/19460%9/3426%2.31.3-4.1 Ham111/18759%17/3845%1.30.9-1.3 Beef110/17663%19/4939%1.61.1-2.3 Potato salad103/16961%22/5342%1.41.0-2.0 Pasta salad90/14164%32/7046%1.41.0-1.8
29 Dose response for chicken consumed by those who reported ill after attending the luncheon Chicken servings N= 49 IllNot ill Relative risk 95% CI 018Reference 117 4.50.6-29.4 2717.81.2-50.9
30 Laboratory results Disaster! Stool samples lost for 2 days Stool samples had low counts of clostridium perfringens spores (< 10 6 spores per gram) Laboratory comes to our rescue with Pulsed Field Gel Electrophoresis
31 PFGE of C. perfringens outbreak .. Similar pattern suggesting common exposure
32 Prevention Food inspector blitz on caterers Entered into our database –Yet more evidence that “weekend” and “offsite” catering is associated with outbreaks due to inadequate temperature control
33 Was this a model outbreak? Common pathogen Good and rapid case finding Aggressive collection of stool specimens –Did not rely on health clinics or hospitals Epidemiological techniques including dose- response analysis helped identify the chicken Close liaison with laboratory enabled novel testing that confirmed cause
35 National Outbreak Register Outbreak register Centralized collection of outbreak reports Retrospective Data collected one quarter in arrears Accuracy and completeness Data accessible through ad hoc data requests
36 Outbreak Register – Key Fields Outbreak sequence number Year, first case onset, last case onset State Number ill, hospitalised, died Setting food prepared Mode of transmission Vehicle Remarks
37 Outbreak Register – Data Updated to September 2007 (except VIC) 4688 outbreaks –638 (14%) foodborne or suspected foodborne –3598 (77%) person to person –108,421 people ill –3058 hospitalised –120 deaths
38 Foodborne Outbreaks, 2001- Sep 2007 638 foodborne or suspected foodborne outbreaks –10,424 people ill –815 hospitalised –13 dead Setting –40% in restaurants Aetiology –31% Salmonella species 73% Salmonella Typhimurium –39% Unknown
39 External Data Requests Requests received from –Industry partners –Government partners –General public –Academics Many parties interested in the data
41 Egg-Associated Outbreaks 75 egg-associated outbreak reports from January 2001 to April 2007 –1222 cases, median 9.5 (2-213) –361 hospitalised, 3 deaths Data provided to FSANZ Standards Development Committee (developing primary production standard)
43 Enhanced Data, Egg-Associated Outbreaks Collected enhanced data on 67 of 75 egg-associated outbreaks 58% (39/67) associated with uncooked eggs 84% (56/67) Salmonella Typhimurium 37% (25/67) had environmental testing of farm –76% (19/25) of these were positive for Salmonella (many serotypes) 28% (19/67) - sampled eggs from farm –31% (6/19) of tested eggs were positive for Salmonella Outbreak register helps define risk factors, environmental conditions and completeness of public health response
44 Key Themes Increase in egg-associated outbreaks Catering industry (raw egg use) Bakeries including “Vietnamese Style” Private homes (raw egg use) Improving investigation Same strains in patients & farms Greater understanding of egg types and sources Intervention for prevention Egg Food Safety Summit Primary Production & Processing Standard
45 Evidence supports government statements on eggs
47 Integrating high risk foods and setting risk Ministerial Policy Guidelines on Food Safety Management in Australia: Food Safety Programs www.foodsecretariat.health.gov.au/pdf/food_safety.pdf
48 Data used for decision making… Summaries of multiple outbreaks of Individually Quick Frozen Oyster meat from Japan and Korea were used to convince regulators that the risks posed by these foods was too high. Standard setting for foods such as –chicken –meat, –eggs, –dairy products and –seafood. Deaths associated with foodborne outbreaks in aged-care facilities and hospitals supported Food Safety Programs for Service to Vulnerable Persons Data used for quantitative risk assessment Number of outbreaks of “unknown pathogens” highlights need to improve specimen collection and laboratory capacity
49 Summary Good outbreak investigation requires: –Training –Mentoring –Lots of practice –Standardised case definitions, data handling and reporting –Enthusiastic field investigation including environmental inspection and clinical specimen collection All outbreaks summarised in national database to provide ongoing lessons for prevention.
50 Thank you Acknowledge the assistance and work of others in investigation of these outbreak, compiling data and contributing presentation material - Mary Osbourn, Philip Bird, Martyn Kirk, Katie Fullerton and OzFoodnet epidemiologists.