Investigation of waterborne outbreaks

Transcription

1 Investigation of waterborne outbreaks Athens, 19 th April 2016 Dr Gordana Kuzmanovska National Public Health Institute, FYROM

2 Learning Objectives Learn specifics during WB outbreaks investigation (10 steps of outbreak investigation) Understand the operational aspects of outbreak investigation and response through Examples of different WBOs o in peacetime, and o in times of disaster Get acquainted with outbreak risk communication

3 Goals. Why investigate an waterborne outbreak? Prevent further illness/cases! Identify the cause and stop the outbreak Understand what happened and why Prevent future outbreaks Improve our knowledge on main causes Train and learn Maintain trust Better prepared for next event!

4 Sudden start, explosive flow - many people affected (huge size). Duration of outbreak the length of incubation period. Epidemic curve - steep upward trend and somewhat mitigated the downside (point source outbreak, intermittent source, continuous contamination,person-to-person transmission) Extended end of outbreak - contact transmission (epidemic tail!) Territorial distribution - coincides with the territory supplied with water from the same source! Control groups - positive controls as well as negative controls - clarification of the epidemic Multiple causative agents - several agents with different incubation Water wave before the epidemic Outbreaks often follows by supporting defects in the water supply or sanitation:. No seasonal character Characteristics of WBOs Small infective dose - the cause of prolonged incubation of the disease outbreak Not identify the causative organism in the water - typing, sub-typing sequencing

5 Steps in the outbreak investigation 1. Detect and confirm outbreak and diagnosis 2. Form Outbreak Response Team 3. Define a case (case definition) 4. Identify cases and obtain information 5. Describe data by time, place, person 6. Interview cases and generate hypothesis 7. Test hypothesis: analytical studies 8. Additional studies (microbiology, environmental) 9. Inform risk managers, implement control measures 10. Disseminate findings, conduct evaluation

6 1. Detect and confirm outbreak Health care system Increased cases - detection by surveillance systems Reports from health care facilities, doctors Lab receive many fecal samples Other signals: Increased absenteeism from work, schools Increased sales of anti-diarrheal medications Complaints on water quality Routine samples with faecal indicator bacteria Failure with water treatment or distribution system Media reports

7 Problems/chalenges in detecting WBO Few go to doctor with diahrrea Mistaken as normal winter vomiting disease Pathogen often unknown Pathogens with long incubation period Not known problem at waterwork; routine samples with normal results

8 1. Confirm outbreak and diagnosis Is this an outbreak? More cases than expected? Surveillance data Surveys: hospitals, labs, physicians Caution! Seasonal variations Notification artefacts Diagnostic bias (new technique) Laboratory confirmation - serology - isolates, typing of isolates - toxic agents Meet attending physicians Contact (visit) the laboratories Do not wait on lab results to start the investigation! Not necessary to confirm all cases!

9 Example 1: Campylobacter outbreak in Røros, Norway. May 2007 Background: UNESCO world heritage site: mining town built exclusively of wood. Population 5.600, tourists ~1 million / year Ground water - not treated National regulations on drinking water saffety

10 Background: Epidemiological situation Campylobacter Røros Campylobacter - most commonly reported bacterial cause of gastroenteritis in many developed countries and Norway! Laboratory confirmed cases - notifiable to the Norwegian SSCD. Most frequently identified pathogen in reported WBO (26%) in Norway Drinking untreated water - leading risk factor for campylobacteriosis in a case-control study in Norway from ! The source of infection frequently remains unknown.

11 Campylobacter outbreak in Røros May 2007 Campylobacter Røros Monday 7-th May: Clinician reports of cases of diarrhoea in Røros (weekend) (signal) Clearly more than expected! (DETECT OUTBREAK???) Tuesday 8-th May: Schools and offices report high abscenteeism "Not to worry likely winter vomiting disease" "we do not suspect the water Statement of those responsible - public health authorities Wendsday 9-th May Hundreds suspected Water samples negative - it s not water?! Friday 11-th May: few positive stool smaples on Campilobacter jejuni (CONFIRM DIAGNOSIS)

12 Outbreak confirmed, asamble response team! Campylobacter Røros 11-th May: Suspected up to cases A few stool samples positive for Campylobacter jejuni Meeting of the outbreak response team Municipal health officer Food safety authorities Waterworks personell NIPH advisor Others? OUTBREAK CONFIRMED!: Further investigations warranted! Team coordinates: Field investigation (pilot study!) Question : water?? Start chlorination Roles and responsibilities Epidemiologist Environmentalist: - Water specialist - Water engineer - Food safety expert Microbiologist Clinician Veterinarian Representatives from the local utility responsible for water and sanitation...

13 3. Case definition Campylobacter Røros 1000 cases reported in media. real cases? Case definition established!!! Casse clasiffication! Probable case: Person living in Røros, with diarrhea, OR at least 2 of the following symptoms, lasting min. 2 days: Nausea, vomiting, cramps, stomach pain, flatulence, blood in stool, fever and, illness onset between 1 st and 14-th of May 2007 Confirmed case Probable case with confirmed campylobacter!

14 4. Identify cases and obtain information Why: Determine extent of outbreak Find clues to the source / modes of transmission Treat cases Prevent secondary transmission (food handlers, health workers). How? Retrospective case finding Prospective surveillance Passive or active surveillance Media announcement Phone surveys Schools, nursing homes, work places

15 4. Case finding Campylobacter Røros National surveillance system Regional microbiological lab Contact clinics and health care institutions in the municipality Check records, reports (retrospective case finding - passive, active) Collect information about new cases who meet the criteria for case definition (prospective surveillance passive, active)!

16 5. Describe data by time, place, person Unique identifier The line list! Time Place Person Outcome Lab Uni. ID OnsetDate Water Block City Age Sex Hospital Death Sample Result 1 1-Mar-05 A 2 HYD Y Campy 2 3-Mar-05 A 1 HYD N Mar-05 - HYD Y Campy 4 6-Mar-05 - B 3 SEC Y Neg

17 Describe the outbreak - Time Campylobacter Røros Histogram Distribution of cases by time of: onset of symptoms diagnosis identification Describe start, end, duration peak outliers Time of contamination Detection Chlorination Include important events!!! 5 Helps to develop hypotheses! May 2007

18 Place of residence, work, travel Geographic spread and clustering Draw a map! Cases Other geographic points Water sources Animal distribution Roads Restaurants, shops, slaughterhouses, dairies, industrial capacitis Identify area at risk! Describe the outbreak - Place

19 Describe the outbreak - Person Number of cases, attack rate Age Sex Occupation Male Female > Kvinner Menn Clinical presentation Lab results Risk factors Deaths, case-fatality rate

20 6. Interview cases and generate hypotheses Questionnaires/interviews - any common exposures??? Review all available information : Patient Person - Age, sex, ethnicity, occupation.. Place, Time Environment Inspections, controls, contextual info Risk assessments... any incidents? Agent Incubation period, modes of transmission, known food or water sources... (literature)

21 7. Test hypothesis Analytic epidemiological methods Cohort - attack rate exposed group - attack rate unexposed group Case control - proportion of cases exposed - proportion of controls exposed Interview: - Short (questionnaire) - Based on hypotheses - Patients and controls Analysis: - Statistical analysis - Compare exposure cases vs non-cases Identify risk factors

22 Design: Retrospective cohort study Objectives: Identify source water? Describe and estimate burden Identify distribution of cases by water supply zones Campylobacter Røros Cohort study: random selection of waterworks customers telephone interviews in 105 housholds Case definition: Person living in Roros, with diarrhea OR at least 2 of the following symptoms, min 2 days: Nausea,vomiting, cramps, stomach pain, flatulence, blood in stool, fever from 1-st to 14-th of May 2007

23 Cohort selection Campylobacter Røros 345 household members (141 hh - Røros and Holthalen): All asked about symptoms! 105 hh met case def (Roros, Holthalen) One random person in each househols (R) asked about detailed exposures! 101 only from Røros AR% low, high, both zones (RR=ref, 1.3, 1.6 no diference among water zones ) Red dots: sick (47) Yellow dots: not sick (54)

24 Attack rate by waterworks/water zones Campylobacter Røros Water exposures in Røros and neighbouring Holtålen, May 2007, including all household members in the cohort (340) Exposure Cases Total exposed AR % RR (95% CI) Fishers exact p Holtålen waterworks Røros waterworks ref ( ) < Attack-rate = 42% (102/243) total (105/340 AR=31%) Estimated number of cases (4 out of 10 ww. customers) Next phase - AR% Røros high AR=37% (ref) Røros low AR=50%, both zones AR=59% (RR= ref, 1.3, 1.6 no diference among water zones )

25 Attack rate by amount of tap water consumed among selected household members Campylobacter Røros AR% from 0%-70% Dose-response: 2 for linear trend = 8.1 p=0.004 The risk of illness increased with the amount of daily consumed tap water!

26 Environmental investigation: 8. Additional studies - confirm the hypothesis Waterworks details: 1,2,3 (wells, thanks..) Events A, B, C, D maintenance work - 30 April (A) with closed valve (B) (contaminants may have entered the distribution system on the breakpoint) maintenance work - 2 May (C) (little risk), firemen exercise at the airport - 3 and 10 May (D) (sudden episodes of low pressure) low pressure observed at slaughterhouse and diary - 3 and 10 May (E), and coliform bacteria proven in a tap water sample from dairy - 9 May (F).

27 25 Environmental investigation Campylobacter Røros Inspection: Protected wells, good raw water quality 20 pressure fall Parts of distribution network very old pressure fall (since 1910, main parts constructed in 1979) Varying material (300m wood piping - RL, from 1942) 15 High leakage 40% (2006) 10 maintenance work chlorination Mainenance procedures: work/changing waterpipe Incidents: several unstable pressure episodes (Pressure fall reported by users, ww.personel didn t follow procedures for chlorination after work of distr.sys.) May 2007 Other PROBABLE CAUSE OF THE OUTBREAK Weather: High amount of rain before the outbreak, water and melting snow on the streets of Røros centre. Other: Birds on top of the wells, elevated reservoir? Incident: Digging of well 3 destroyed filtering layer

28 Microbiological investigation Campylobacter Røros Clinical samples Tested on: Salmonella, Shigella, Yersinia, Campilobacter; Adeno-Rota-Noro-Astrovirus; Giardlia, Clostridium Difficile and Cryptosporidium oocysts and Giardia cysts 32/61 tested for Campylobacter in total - 52,5% positive 25/26 total analized samples for genetical similarity - 96,1% had identical genetic profile (AFLP) Water samples Routine samples every 14 (7) days 7 different location - OK! Additional samples from different locations negative Coliforms in only one sample from distribution network main water intake at Røros dairy - May 9th Campylobacter negative (11 May and other)!

29 Categorizing levels of evidence in waterborne outbreaks A - Microbiology Same pathogen identified in cases and in water C Analytical epi Evidence from an analytical epidemiological study (case-control or cohort) B - Environmental Water quality failure or water treatment problem, but pathogen not detected in water D Descriptive epi Descriptive epidemiology suggests water, and excludes obvious alternative explanations Strong Probable Possible A+C or A+D or B+C B+D or A only or C only B only or D only Tillett et al. Epid Inf 1998 (120)

30 Conclusions Campylobacter Røros Large waterborne outbreak - 4 out of 10 Røros waterworks customers. No difference in attack rates between the higher and the lower area of Røros (statistically significant result between Roros nad Holtahalen citizens) Strong association between amount of tap water consumed and illness. The cause of the water contamination was not identified! The identical genetic profiles of C.jejuni - common source of the outbreak. 3/18 samples positive tested for parasites - sewage contamination??! (Other detected pathogens in the stool samples - sporadic cases) The most probable time of infection - around 1 May Some cases fell ill after 11 May - might be due to a longer incubation period or prolonged water contamination (person to person transmission uncommon for Campylobacter) At the months with continuous chlorination following the outbreak, no further cases were reported. Multiple faults discovered affecting the Røros water-distribution-system security: Leakages in the system - increased risk of gastrointestinal illness. Low pressure incidents - intrusion of the microorganisms from the soil (close sewage pipe?). The maintenance work on 30 April was done in vicinity of the slaughterhouse and dairy

31 9. Implement control measures Campylobacter Røros Eliminate the source of infection! Immediately: Advise to the public (boil drinking water, drink bottled water) Correct failure, start treatment if needed, use reserve source (drinking water chlorination) Long-term control measures: Protection of storage tanks, wells Replace old distribution pipes Sampling weekly frequent Improve routine procedures for distribution system maintenance and pressure monitoring in risk areas Additional water treatment: UV-treatment

32 10. Disseminate findings, conduct evaluation Regular updates during the investigation Detailed report at the end communicate public health messages influence public health policy evaluate performance training tool legal proceedings

33 Example 2: Cholera outbreak in Haiti - October Background A History of Poverty and Poor Health Life expectancy at birth is 61 years Estimated IMR is 64/1.000 live births, the highest in the Western Hemisphere. Estimated 87 of every born-children die by the age of 5 years >25% of surviving children experience chronic undernutrition or stunted growth Maternal mortality rate is MM=630/ live births. Childhood vaccination coverage is low - 59% for polio, measles/rubella, DiTePer vaccines Haiti the only Caribbean island where malaria remains endemic. Only half of the Haitian population has access to health care! Before the earthquake, only 63% of Haiti s population had access to an improved drinking water source, and only 17% had access to a latrine!

34 Earthquake in Haiti - aftermath 12-th January 2010 an earthquake occured in Haiti Approximately 3.5 million people affected dead, injured people Earthquake inflicted significant damage particularly critical infrastructure water and sanitation - NO LONGER USABLE. health systems. Immediate health priorities include providing shelter, food, clean water and sanitation MSPP requested assistance from the CDC International offers of humanitarian aid - coordination challenges!

35 The cholera epidemic I 19 th October 2010, MSPP was notified of unusual increase of cases with acute watery diarrhoea and dehidratation in one hospital / stool specimens taken 21 th October 2010, first cholera case confirmed in National Laboratory of Public Health (sent to CDC for confirmation/additionally analysis) Toxigenic Vibrio cholerae O1, serotype Ogawa, biotype El Tor (South East Asian strain) th October Initial EPI investigation in 5 hospitals Artibunite Department Health authorities immediately advised community members : boil or chlorinate drinking water, and bury human waste!!! First cholera outbreak after more than a century No experience in managing cholera outbreaks Susceptibility of the population

36 The cholera epidemic II First 10 weeks of the epidemic cholera spread to the 10 departments Number of cases as of 13 th Nov: hospitalized/992 cholera deaths/620 hosp. deaths 63% of cases, 63% of deaths in Artibunite Dept (accor. MSPP) Rapid spread of the outbreak and high initial CFR - 5 immediate priorities: 1. Prevent deaths in health facilities 2. Prevent deaths in communities 3. Prevent disease spread by promotion of safe practices 4. Conduct field investigations to define risk factors and guide prevention strategies, and 5. Establish a national cholera surveillance system to monitor spread of disease. 36

37 MSPP Cholera Response Action Plan Prevent deaths in health facilities, communities and health promotion (priorities 1,2,3) : Focus the response on three lines of action 1. Community level Social mobilisation, health promotion Oral Rehydration Points (ORPs) 2. Strengthening of primary healthcare centres 3. Setting up: Cholera Treatment Centres (CTC): beds Cholera Treatment Units (CTU): < 20 beds

38 MSPP Cholera Response Action Plan Conduct field investigations to define risk factors and guide prevention strategies (priority 4) COMMUNITY SURVY UNDER WAY! Objective: Guide the public health response - knowledge about: how cholera is being transmitted which interventions were most effective how well the population was protecting itself

39 National Surveillance of Rapidly Spreading Epidemic MSPP immediately sets up National cholera surveillance system (priority 5) Reporting on daily basis: cases, hospitalization, deaths (hosp./community) Aggregated data two age groups: 5 years and 5 years! Case definition / classification: Suspected - Acute Watery Diarrhea AWD (more than 3 or more stools/day, without blood) Probable - Suspect case + epi-link with confirmed case, any person died from AWD Confirmed case - A suspect / probable case + lab. Confirmation! Cholera affected Departments - lab confirmed case (by culture of V.cholerae)

40 By mid December: CFR for hospitalized case decreasing In January 2011: Reported cases decreased substantially National CFR of hospitalized case fell below 1% As of July 31, 2011: Total of cases, hospitalized cases (53%) deaths reported (CFR=1.4%) Situation - Course of outbreak

41 Field investigation results/ph responce Untreated drinking water - the primary source for cholera People unaware of how quickly cholera kills Water and seafood from the harbors contaminated with V. cholerae Established resistance of epidemic strain to many antimicrobial agents All epidemic V. cholerae - isolates shared the same molecular markers (point source introduction!).

42 Preventive measures - immediatelly! Educating the public reducing the risk of cholera o Messages, banners, posters (Improvements in Water, Sanitation and Hygiene) o Early investigations affirmed the public s need for 5 basic messages: 1) Drink only treated water (boil, chlorinate!) 2) Cook food thoroughly (especially seafood) 3) Wash hands (often with soap and water)! 4) Seek care immediately for diarrheal illness 5) Take/Give ORS to anyone with diarrhea. Improving water, sanitation-wsh cluster cons. Chlorination-piped water supplies, distribution of water purifying tablets in homes provided water storage vessels, soap..

43 Preventive measures - reduce consequences Increase capacity for cholera treatment! (managed by MSPP, with technical assistance from the International organizations (PAHO, USG, OFDA, CDC.) Increasing the number of: CTC, CTU, ORPs and essential cholera supplies Training clinical caregivers Training materials (in French and Creole): guidelines on cholera treatment, guidelines on effective antimicrobial drug treatment Training-of-trainers workshops Training community health workers: staffed local first aid clinics Taught health education classes, and Led prevention activities in their communities (exmp. how treating drinking water by using water disinfection products; how to triage persons coming to a primary clinic with diarrhea/vomiting; how making and using ORS; how disinfecting homes, clothing, and cadavers with chlorine bleach solutions).

44 Chalenges of WBO investigation Epidemiological aspects High number of cases Difficult to recall all exposures Huge publicity - recall bias Dificulties to find unexposed people Environmental aspects Failure may be short go undetected Difficult to inspect whole system Combination of factors Microbiological aspects Contamination episode short Multiple ethiological agents Water sampling too late no indicators / pathogens left Need to be interpreted together!

45 Risk communication Many communication failures delayed outbreak control undermined public trust and compliance prolonged economic, social and political turmoil WHO: Communication expertise has become as essential to outbreak control as epidemiological training and laboratory analysis.

46 Key elements of outbreak communication TRUST Build, maintain or restore - involvement and transparency are key factors to build trust Trust is hard to win and easy to lose! ANNOUNCING EARLY The first announcement is critical! Be careful inform your partners first (common strategy) state clearly TRANSPARENCY Easily understood, complete and accurate info Explain the unknowns and the limits Barriers: Fear of economic loss/revealing weaknesses, bad planning and preparation, no training THE PUBLIC Understand the public s beliefs, opinions and knowledge! Always tell the public what they can do to reduce risk! The mass media represent the public! PLANNING Risk communications expertise must be integrated into each stage of the outbreak management put it in preparedness plan! Everything you do is communication!

47 Thank you! Dr Gordana Kuzmanovska National Public Health Institute, FYROM