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Trinity College Courses
Caroline Barakat

HLTC07: Patterns of Health, Disease, and Injury Lecture 4: Epidemic investigation Lecture Outline  Outbreak detection  Preparing for an investigation  Objectives for an epidemic investigation  Steps in an epidemic investigation o Confirmation – an analytic approach o Case definition o Case ascertainment o Descriptive epidemiology  Tie in to tutorials - Odds and relative risks o Hypothesis and testing o Communication  Wrap-up and implications  Application o Food contamination problem that we’re experiencing right now - apply Introduction  Key roles of public health agencies– manage outbreaks that endanger the public’s health  Nature of outbreaks can vary o Outbreaks can be E.coli, infectious diseases, zoonotic diseases, chronic diseases, injury, exposure to toxic agents, any type of health-damaging behavior o Public health agencies have the mandate and key role to manage these situations  Cause can also vary o Can be contamination (cross); incidental, accidental or intentional and if it’s an outbreak then it falls under the role of public health agencies to protect public  Speed, coordination and informed judgements are critical o If not, will lead to further damage  Each outbreak = learning processes and each of the outbreaks generates new policies/procedures  Picture of bird flu mutation study which led to the slaughtering of many chicken – leads to these kinds of activities; important = speed and coordination and that informed judgements form the basis for the decisions Outbreak Detection  An increasing number of persons who are showing a specific clinical pattern that is unusual for a certain  Situation or location = would classify as an outbreak; anything beyond what’s normal for that place and time  Two main ways to detect outbreaks: 1. Active surveillance– normal or contact reporting – required: sensitive and monitored surveillance system where the data are collected in a timely manner and regularly analyzed o Normal reporting to health agencies OR o Done through normal reporting Ex: health departments contacted by professionals (doctors, nurses, etc.) to report the outbreak o Health care professionals can aim to contact a specific health agency to let them know of specific cases that they’ve encountered o Ex) HIV/AIDS – recognizing this disease in the 1980s largely generated from physicians that saw many diff types of cancer – referred to as active surveillance and contact reporting (contacted health officials and told them what they were seeing – seen unusual # of cases of specific disease) o Pre-requisites for active surveillance is to ensure that you have a sensitive surveillance sys – one that is monitored very well where data are collected in a timely manner and systematically and then analyzed systematically 2. Syndromic surveillance – ex: ICD10 or 911 calls monitoring o They monitor non-specific clinical syndromes o Not specifically focus on persons, but rather on populations o Refers to the surveillance of health data of pop’ns and is distinct from active surveillance in that it doesn’t really apply to individuals – aggregated altogether o Not collecting from individual level – just aggregating them o In reference to the recent E.Coli outbreak – need to know the specific molecular subtype – there’s databases like PulseNet (origin – US) – that do molecular subtyping – looks to survey food quality / contamination – not individual level = aggregated Diagram  Generated by Public Health Agency of Canada that looks @ surveillance  If an individual comes up with some sort of disease or many people with certain disease  First level that receives info is the Local Public Health unit – there’s ‘x’ # of outbreaks  They will relay this info to diff provincial levels – provincial health/agricultural authority or other – depending on which mandate it falls under, can send it to more than one agency – communication and Xchange of info should occur at all levels  Eventually, provincial health agencies are notified – public health agency of Canada and Canadian Food  and Agri Agency, RCMP etc; are notified of a certain outbreak – leads to public health alert @ local,  provincial, federal and some mandates = international agencies like WHO – for certain outbreaks  This is in a nutshell, active surveillance in Canada meaning that we’re collecting data on individuals or individual outbreaks and how we put it altogether so that ppl know about the outbreak – surveillance based on individuals  Syndromic surveillance – there are researchers who work with those databases (ex: ICD-10, 911 calls etc;) and they can collect this info and submit report and let ppl know what the report shows – takes a longer period of time  Active surveillance and syndromic surveillance may both identify a certain outbreak but it very much relies on the nature of the outbreak o Ex) infectious diseases – not going to wait for syndromic info to let us know that there’s an outbreak; need active surveillance – surveillance @ the health practitioner level – letting officials know that there is an outbreak of a certain disease Example of Syndromic Surveillance in Canada:  ‘CFIA investigation into XL Foods’: o The CFIA and XL Foods, Inc., are warning the public, distributor and food service establishments not to consume, sell or serve various raw beef products that may be contaminated with E.Coli 0157:H7. The CFIA is working with the recalling firms and distributors to identify and verify all affected products. There is a strong possibility the CFIA’s food safety investigation will identify additional products meaning the recall should be expanded. Consumers who were unsure if they have affected products are advised to check with the store where they were purchased. If you are unsure whether a product is part of the recall, the safest course of action is to throw it away.  Another example of syndromic surveillance: o Bacterial contamination of Walkerton well – E.Coli contamination o Molecular subtyping done in this case – see if aquifers connected = contaminated – letting ppl know which wells they’re associated with and which is contaminated  Whichever way the surveillance activity is done, syndromic isn’t really referred to at the individual level; it looks @ molecular subtyping, identifying the certain source and proceeding with some kind of surveillance at that level  These were diff ways that outbreaks can be DETECTED; epidemic investigation, first step is to detect an outbreak o Have there been cases? o Was molecular sub-typing done? o Are they linked to one thing? o After outbreak detected, can move onto preparing for an investigation Preparing for an Investigation  Usually starts with the local public health authority/agency; WHO may be involved if international investigation and they have GOARN  Global Outbreak Alert and Response Network (GOARN) o A technical collaboration of existing institutions and networks that pool human and technical resources for rapid identification, confirmation and response to outbreaks of international significance.  Public health authorities at appropriate governmental levels, local and reference laboratories o Info exchange o And it moves its way up and it can reach agencies like WHO, if international significance  Who receives info related to investigation? o Public health authorities @ all governmental levels o Local and reference labs – to prepare for processing of certain specimens assuming that outbreak has to do with some kind of lab testing  Core team should be assembled (with diff expertise) – can consist of epidemiologists, lab technicians, communications specialists, statisticians – depends on what you’re doing 1) Established a hierarchy for decision and information sharing 2) Create objectives for investigation (systematic in nature) 3) Develop plans for re-evaluating the objectives as new info comes up 4) Delineate roles and responsibilities for the relevant agencies o The objectives change as the investigation evolves; the roles and responsibilities may also change and be re-defined 5) Lead agency and principal investigator o Running the process by assigning tasks 6) Assess need for additional human resources 7) Gaps in expertise o Do we have the expertise to start an epidemic investigation or do we need to fill in certain gaps in expertise?  If this step isn’t done, there may be chaos that develops Laboratory Preparation  Certain steps taken in preparing for lab section of epi investigation: 1. Develop specimen collection and shipping protocols – ex: specimen type, quantity, timing, type of containers, transport media, preservatives, labels, pre-shipping requirements, instructions for shipping o If these things aren’t done properly, may get false positives/negatives 2. Develop specimen processing and testing protocols – tests each lab will conduct, how the results will be determined and interpreted, how results and to whom results will be released o In some cases, levels need to be selected – anything above a certain level implies something and below it implies something else o If everything is made available to everybody – create chaos maybe; if info not available, this would deter an epidemic investigation 3. Obtain the materials and supplies and ship to the outbreak location o Materials: collection kits, testing reagents, preservatives for certain specimen, labels – make sure join up with other agencies and send out proper materials early 4. After collection – ensure proper labelling and tracking  Not all outbreaks allow for this kind of prep, but if they do and they require lab prep, then it’s important that this is coordinated in the preparatory phase of outbreak investigation Objectives of an Epidemic Investigation  Objectives would include: o Stop the spread/reduce damage o Find source/cause and deal with that (in some cases could change from epidemic investigation to environmental investigation) o To learn (always an underlying objective in all epidemic investigations) o How do we tighten things? Certain outcomes = certain regulations Objectives (1)  ‘On Oct 8, 2000 the Acting Director of Health services in GULU District, Uganda, received 2 reports concerning unusual illness and deaths. One day later, an outbreak investigation was launched and 2 days later, the first intervention to contain the outbreak were instituted: An isolation unit was set up in the local health-care facility, protective material for health staff was dispatched and the public was alerted of the risk of infection during funerals. On Oct 15, the National Ebola Task Force (core team) was constituted to coordinate and mobilize resources for the outbreak, which lasted more than 4 months. A total of 425 confirmed cases of Ebola were recorded, w/ 224 deaths among them. o Objective of investigation (of core team): Reduce the amount of infection; limit the spread of that particular infection (prevention) Objectives (2)  Between Feb 2003 and May 2004, ten outbreaks of GI illness among schoolchildren at 9 diff schools were reported to the Dept of Public Health. All the children ate lunch provided by the schools and the disease was characterized by short incubation periods and short durations of illness. Based on prior investigations, a biotoxin or chemical agent was suspected. An environmental investigation identified 3 distributors who provided the schools w/ tortillas of diff sizes and under various brand names but from the one manufacturer. Several deficiencies at the plant were noted such as improper storage, use, labeling of chemicals, food ingredients and additives, and food contact surfaces weren’t protected from environmental contamination, Samples were collected and analyzed. After the manufacturer was informed about the suspected cause of the outbreak, the recipe was changed and the amount of calcium propionate and potassium bromate was lowered. o Objectives of investigation (of core team): Identify source/origin of the disease – traced back to some kind of environmental investigation in this case  Sometimes it can be all 3 objectives and also the learning component: o Ex) SARS: first objective = control the disease o Task force may also want to know what caused the illness o Ex) Gastrointestinal illness – many things can cause  Obviously you want to reduce the illness but the primary objective could be to find out what’s causing GI illness in order to be able to reduce illness  For the most part, for infectious diseases, the primary objective would be to limit the disease; but if it’s something related to diarrheal diseases and other things that are common but we don’t know what the cause/ what kind of contamination – the primary objective would be to figure out the cause/etiology so you can limit disease Objectives (3)  In the fall of 1996, 70 cases of E.Coli 0157:H7 infections were epidemiologically linked to a particular brand of unpasteurized apple juice in Canada; four persons developed hemolytic uremic syndrome, and one person died. Recalled apple juice grew E.Coli with the same PFGE pattern as those from the case isolates. The magnitude and severity of this outbreak lead the FDA to propose 2 new regulations. First, all unpasteurized fruit and vegetable juices would have to carry a label stating, “Warn
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