Lecture 7 Managing Outbreaks PDF

MANAGING OUTBREAKS AND INFECTIOUS DISEASE EMERGENCIES Professor Angus Cook, School of Population and Global Health Specific learning outcomes On completion of this topic, you should be able to: • Describe the key concepts in communicable disease control • Describe the key measures in infectious d...

MANAGING OUTBREAKS AND INFECTIOUS DISEASE EMERGENCIES Professor Angus Cook, School of Population and Global Health Specific learning outcomes On completion of this topic, you should be able to: • Describe the key concepts in communicable disease control • Describe the key measures in infectious disease surveillance and outbreak control • Outline the steps in managing outbreaks and infectious disease emergencies I. KEY CONCEPTS IN COMMUNICABLE DISEASE CONTROL Outbreaks and epidemics: BASIC DEFINITIONS Outbreak = often used to refer to an increase in the number of infections that is relatively localised (or confined) in time and space may occur in such specific locations as schools/residential facilities Endemic = the ‘usual’ or ‘expected’ persistent level of disease in a given area/community IE ‘steady background state’ of the infection VERSUS Epidemic = a rise in case numbers above the background or ‘expected’ rate of the disease in a community/region or arise from events such as contaminated food sources at a local restaurant Perth) Pandemic • Strictly defined as “any epidemics that cross international boundaries and affect a large number of people worldwide” BUT • In practice ‐ usually applied to infections that pose a serious risk to public health IE cause severe illness + to which there is little population immunity • Does not include cyclical/seasonal infections such as ‘regular’ seasonal flu • The World Health Organisation and other agencies often use formal definitions for pandemic “phases”: from a few human cases …up to the efficient and sustained disease spread from person to person in different global regions. The WHO developed these “phases” to (i) help inform and communicate with the public and health agencies; and (ii) trigger public health responses. ADDITIONAL TERMINOLOGY IMPORTANT IN UNDERSTANDING INFECTIOUS DISEASE CONTROL • ISOLATION This refers to the separation of already infected persons during their period of infectiousness (when they could transmit the infection) For example, patients may be confined in a hospital or at home. Different forms of isolation are required for different infections. • QUARANTINE This refers to the separation of those who may be potentially capable of transmitting disease, but who are currently free of signs or symptoms of illness.  In other cases, PRECAUTIONS rather than total isolation may be used, such as special handling of bodily wastes in people with gastroenteritis • INFECTIOUS DISEASE SCREENING = one of the MEASURES TAKEN ONCE AN INFECTION EVENT (OR OUTBREAK) HAS OCCURRED IN ORDER TO STOP PROGRESSION OR TO LIMIT FURTHER SPREAD. Includes: • early detection and management of individuals who may have become infected, often while they are still asymptomatic or at an early stage in the progression of the disease • CONTACT TRACING and CASE FINDING e.g. screening of known contacts of a person with tuberculosis e.g. for STIs: contact tracing and screening of sexual contacts of cases of gonorrhoea, syphilis, chlamydia, hepatitis B and HIV infection. e.g. stool cultures may be taken from household contacts of cases of salmonellosis and other notifiable gastrointestinal infections.  Once located, the cases are treated (e.g. with antibiotics) and/or given advice to limit transmission II. KEY MEASURES IN DISEASE SURVEILLANCE AND OUTBREAK CONTROL Defining surveillance in an infectious disease context • Surveillance in this context is defined as an ongoing, systematic collection, analysis and interpretation of health‐related data essential to the planning, implementation, and evaluation of population health initiatives • Surveillance systems form the foundation of successful infectious disease control allow communities to anticipate the emergence of infectious diseases support outbreak responses facilitate monitoring and evaluation of responses LEVELS OF SURVEILLANCE • Note that if the disease is very severe, such as Ebola or bubonic plague or meningococcal meningitis, the pyramid will be much more compressed at the base as all cases are likely to come to the attention of the health system. IE we expect that most or all such cases will require urgent treatment in a healthcare setting and that they will end up in the notification system. LEVELS OF SURVEILLANCE One very important characteristic of surveillance systems is that they are not “one‐way” – they cannot just be about “data collection” These systems need to not only collect the information but also to respond in some way to ensure that all the people/agencies who need that information have been properly notified. Once the alarm has been sounded, we need to initiate an effective and timely response. • In NOTIFIABLE DISEASE REPORTING = when certain diseases are identified, health workers must ‐ or are in effect legally obliged to ‐ contact a central public health agency. III. MANAGING OUTBREAKS  STEP ‘0’: BEFORE YOU START…AND AS THE OUTBREAK PROGRESSES… • • • Need to ensure a trained outbreak team and other necessary resources are in place or are readily available  usually requires a multidisciplinary approach e.g. often includes a public health specialist /epidemiologist with field experience, an infectious disease clinician, a microbiologist, and a communications officer In an evolving emergency situation  may need to rapidly set up the required structure and organization = operating centre and relevant command‐and‐control infrastructure with clearly assigned roles and responsibilities Need to consider your communications systems: (i) within the health system; (ii) with other sectors (e.g. police; transport); (iii) with the general population and vulnerable populations  ESTABLISH THE EXISTENCE AND LEVEL OF URGENCY OF AN OUTBREAK • COMPARE USUAL INCIDENCE RATES (‘STEADY STATE’) versus CURRENT RATES TO CONFIRM THE OCCURRENCE OF NEW CASES OF THE DISEASE >>> ARE THE CASES NOW IN EXCESS OF THOSE EXPECTED IE ABOVE THE BASELINE FOR THAT DISEASE? • DO ALL THE SUSPECTED CASES PRESENT IN THE SAME WAY? The “urgency” question: If this a ‘real’ epidemic/outbreak – does it require an urgent response? • An early systematic assessment of the risk or potential threat posed by the infectious disease event is essential to trigger the correct epidemic response • Need to ask: What is the likely public health impact? For example, a newly emerged pathogen with potential to cause a massive outbreak or pandemic usually requires the prompt implementation of measures to contain its spread  CONFIRM AND VERIFY THE DIAGNOSIS • CONFIRM THE DIAGNOSIS USING CLINICAL AND LABORATORY RESOURCES.  we need a reliable source of clinical and laboratory data + confidence that the samples were collected and analysed correctly. • We need to try and determine whether the “cases” that have come to your attention in fact have the same disease • This basic case information is often presented as a line listing in the following general format: CONSIDER TIME, PLACE AND PERSON (‐‐> CLASSIFY THE EPIDEMIC) • TRY TO CLASSIFY THE DISEASE BY TIMING, LOCATION AND THE CHARACTERISTICS OF AFFECTED PEOPLE • (SEX, AGE, PLACE OF RESIDENCE, RECENT ACTIVITIES ETC) • IS THE EPIDEMIC COMMON‐ SOURCE, PROPAGATED OR MIXED? Types of epidemics: COMMON SOURCE EPIDEMICS • Occurs when a group of persons are exposed to a “common” source of pathogens e.g. may be a POINT SOURCE – food poisoning from single source. • The epidemic curve usually rises and falls rapidly. >>> “CLASSIC” EXAMPLE: Salmonella from contaminated chicken pieces at a buffet lunch  large number of people sick soon afterwards Types of epidemics: PROPAGATED EPIDEMICS • The disease continues to spread IE cases occur over and over. • May be person‐to‐person (e.g. COVID‐19/influenza) or by vehicles/vectors (hepatitis B spread from sharing of infected needles for intravenous drug use). • The epidemic curve usually continues to rise as the disease spreads to susceptible individuals [usually eventually followed by a gradual decline]. >>> “CLASSIC” EXAMPLE: Spread of measles in a child‐care centre full of unvaccinated children Cases Propagated / Time  Types of epidemics: MIXED EPIDEMICS • When a common source/point epidemic is followed by person‐ to‐person contact and thus propagates >>> “CLASSIC” EXAMPLE: Bacillary dysentery (a severe form of shigellosis IE infection by Shigella) from a contaminated water source spreads to other people who come into contact with the infected cases Outbreak of the gastroenteric disease norovirus in Finland.  virus was initially picked up from contaminated raspberries – creating a point source infection – but was then passed person‐to‐person to other children in the day‐care centre. POTENTIAL PROPAGATION  FORMULATE HYPOTHESES ON THE CAUSATIVE AGENT AND POSSIBLE MODES OF TRANSMISSION/ WHERE NECESSARY FORMALLY EVALUATE USING ANALYTIC STUDIES (e.g. case‐control or cohort studies) CONSIDER ALL THE LINKS IN THE INFECTION PROCESS: AGENT, RESERVOIR, MODE OF TRANSMISSION AND ENTRY INTO HOST; HOST SUSCEPTIBILITY …Drawing on all the information we have collected for this outbreak PLUS our microbiological and epidemiological knowledge… High on the list of possible components/links in the transmission process include: • water, food and milk supplies • possible contacts, including sexual, recreational or institutional • history of drug use • possible links to occupation • history of overseas travel • animal sources of infection etc  INSTITUTE CONTROL MEASURES An outbreak requires: • THE TREATMENT OF CASES • CONTROL MEASURES TO REDUCE THE SPREAD OF THE EPIDEMIC OR PREVENT ITS RECURRENCE (e.g. improve sanitation/water supply; immunisation) Examples of control measures following outbreaks • Close affected facilities to limit further exposure • Recall or destroy contaminated products e.g. affected foods • Restrict attendance at school/work of infected people • Provide preventive antibiotics and vaccines to high‐risk contacts • Recommend handwashing • Use of public educational messages through an appropriate range of media  DISSEMINATE INFORMATION TO PUBLIC, MEDIA AND OTHER DECISION‐MAKERS • EFFECTIVE COMMUNICATION is a critical part of outbreak management • This includes PROMPT AND ACCURATE RELAYING OF INFORMATION TO ALL STAKEHOLDERS, INCLUDING PUBLIC HEALTH OFFICIALS, HOSPITALS, SCHOOLS ETC • Need to establish and maintain public trust in the authorities – this can quickly be eroded (and in many places, maybe trust in government was not very high in the first place). • Political and health authorities must be transparent and unambiguous in their messages with the public and essential service workforces ….BUT must also try to reduce the risk of large‐scale panic. • Must acknowledge when there is uncertainty and be honest with their messaging. IV. INFECTIOUS DISEASE EMERGENCIES What is an “infectious disease emergency”? • Infectious disease emergency: Events that involve biological agents/diseases and that result in: ‐ Rapidly escalating case numbers (compared to “normal” levels) ‐ Severe clinical disease These events are often associated with challenges in achieving effective community control • Includes: ‐ “New” (emerging) or uncontrolled “familiar” infectious diseases with serious clinical consequences that are causing outbreaks (increases in cases that are localised in time and space eg suburb X over 1 week) or epidemics (broader rises in background rates of disease)  may in some circumstances evolve into a full‐blown pandemic Less common ‐ Intentional release of pathogens (bioterrorism eg anthrax) ‐ Accidental release of pathogens (eg laboratory accident) Recent examples: • 2009 H1N1 (or swine flu) pandemic • 2014 polio declaration • 2014 outbreak of Ebola in Western Africa • 2015–16 Zika virus epidemic • 2018–20 Ebola epidemic in eastern Congo • COVID‐19 pandemic Which kinds of pathogens have or could potentially cause “infectious disease emergencies”? • Usually associated with: *Viruses Examples: ‐ Pandemic influenza eg 1918‐19 Spanish flu; 2009 H1N1 “swine” flu ‐ Coronaviruses such as COVID‐19, SARS (severe acute respiratory syndrome) and (MERS) Middle East respiratory syndrome ‐ Ebola virus ‐ Polio (especially during 20th century prior to widespread vaccination) *Bacteria Examples: ‐ Bubonic plague ‐ Anthrax (eg with bioterrorism) ‐ Cholera Impacts: on health and survival • Pandemics and ID emergencies pose major threats to the population health in terms of morbidity (illness) and mortality (death) • A number of infections with pandemic potential – notably respiratory pathogens – tend to disproportionately affect the very young (such as infants and children under 5), the elderly and those with impaired immune systems or chronic diseases (e.g. heart disease and lung diseases such as COPD) • Serious risk of mental health impacts from events such as bereavement, threat to life, financial loss and displacement arising from the pandemic. Example: COVID‐19 health impacts • COVID‐19 causes minimal/mild symptoms ‐ fever and dry cough ‐ for >85% Clinical picture in more severe cases • Increased risk with age / co‐existing conditions and diseases Eg cardio‐respiratory illness/obesity • Lower risk for infants, children (unlike flu) and younger people • Respiratory distress/failure  often need hospitalisation/ ICU + oxygen /ventilators to support breathing • Clotting abnormalities • COVID‐19 effects on brain, heart and immune system • For those who recover – many have a long period of convalescence/ prolonged fatigue Impacts: on social and economic functioning • Impact of loss of work from illness/shutdowns • Non‐attendance at work from factors such as increased caring responsibilities (either through sickness or school closure), transport disruptions and work avoidance (fear of infections from commuting or at the workplace) • Considerable costs and use of resources in case‐finding, screening and health care provision • Times of crisis, such as pandemics, can help to bring communities together BUT they can also potentially drive division – has been observed in most pandemics over historical time  need to prevent or minimise stigmatisation of groups in pandemic situations How to respond to ID emergencies and pandemic situations? Responses to major infectious disease events involve coordination across multiple agencies and areas of expertise encompass the four principles of emergency management: • PREVENTION (where possible) • PREPAREDNESS • RESPONSE • RECOVERY The World Health Organisation’s “Continuum of Pandemic Phases,” displayed as a distribution curve of the hypothetical global average of pandemic cases over time PREVENTION • If at all possible, we should seek to prevent the development of pandemics in the first place IE if we can identify how diseases are maintained and transmitted, we may attempt to reverse or reduce the disruption of natural balances among hosts, agents and the environment As noted, there are a number of common potential drivers of infections, such as: • uncontrolled urbanisation • climate factors • trade and transport practices • modes of food production • human migration • patterns of animal movements into new habitats These could form the basic targets for prevention strategies • One of the keys to countering these emerging infections is through vigilance and rapid response.  In order to manage infections quickly, we must be able to detect the disease syndrome (distinctive clinical signs and symptoms), the offending pathogen, and we must establish a reliable and accurate process for reporting the information to the appropriate health authorities. • The process of surveillance is essential to success PREPAREDNESS • All relevant government agencies (including health, emergency services, defence force etc) must develop an emergency management plan, practice the plan, and critically evaluate their level of preparedness • Healthcare organisations facilities must be prepared for infectious disease events many infectious disease emergencies will result in a large number of patients requiring hospitalization patients will often need mechanical ventilation, isolation, or expert intensive care facilities negative pressure rooms = prevents the escape of pathogens via airborne transmission from infected patients in the room; (clean) air can flow into the room but only exits through filters/exhaust fans need stockpiles of antibiotics or antiviral medications  staff and support teams need respiratory protection (e.g. respirators) laboratory support eg testing kits/facilities for microbiological analyses RESPONSE • Often the response needs to be rapid and coordinated across many sectors to contain the infection • Cases of unusual diseases OR unexpected “clusters” in time and space should be promptly reported to local public health officials • Hospitals, clinics, nursing homes, and long‐term care facilities will have critical roles in the response includes triaging and isolating patients suspected of having infection in emergency departments and urgent care centers so patients arriving with the disease do not infect others. • The goals of public protection and the taking of personal responsibility for risk minimisation …must be balanced against… interests such as dignity, privacy, and autonomy (eg in terms of restricting personal movement/activities or collecting personal data). *Management of current clinical cases • Early and adequate mobilisation of emergency and clinical services = for some outbreaks, here may of course be a massive influx of sick people, as well as the “worried well” who believe they have the disease but are in fact uninfected • Antibiotics/antivirals if appropriate but curative therapies not available for many infectious diseases – especially new or emerging ones • General supportive therapy and at times haemodynamic stabilisation/oxygen and ventilatory support etc. *Prevention of further transmission Options include: • Clinical and laboratory screening for evidence of early/subclinical infection • Contact tracing of those who have been/may have been exposed to the confirmed or suspected cases • Isolation of infectious people and quarantine of those who may have been exposed to the disease • Social distancing refers to a set of practices that aim to reduce disease transmission through physical separation of individuals in community settings e.g. prohibiting large public gatherings of any kind; encouraging people to work from home • Personal protection e.g. masks; for those infections spread by arthropods ‐ such as mosquitoes and ticks ‐ the use of repellents and protective clothing are simple and effective methods of control. • Vaccination may be an option for some diseases EXAMPLE OF W.H.O. RECOMMENDATIONS (Feb 2020) Table 1. Non‐pharmaceutical public health measures to reduce transmission of COVID‐19 Situation Preparing for large‐scale community transmission of COVID‐19 Intervention Recommended in all situations Hand hygiene Respiratory etiquette Face masks for symptomatic (NB: advice on face mask use has been variable) individuals Voluntary isolation of ill individuals Surface and object cleaning Health advice for travellers Consider, based on local evaluation Avoiding crowding (e.g. mass gatherings) School closures and other measures1 Workplace closures and measures2 1 School measures include exclusion policies for ill children, increasing desk spacing, reducing mixing between classes, and staggering recesses and lunchbreaks. School closures are suggested during a severe epidemic and should be coordinated and proactive, rather than reactive. 2 Workplace measures include teleworking, staggering shifts and expanding policies on sick leave. “Flattening the curve” • Focused on REDUCING THE NUMBER OF ACTIVE CASES AT ANY GIVEN TIME, which in turn gives both health services and other essential services time to prepare and respond, without becoming overwhelmed • The dotted horizontal line is the nation’s current health‐care system capacity – its ability right at the moment to assess and treat people who have the infectious disease • Aim to avoid the large spike of cases that cannot be managed by the health system (blue curve) • Aim to reduce the case numbers to a lower level over a longer time (yellow curve) to keep the cases below the level of maximum heath system capacity…although governments and communities need to be ready for the “long haul” [Health system capacity] “Flattening the curve” • Over time, can also try to lift the dotted horizontal line upwards so that the nation has more health‐care capacity eg intensive care beds/ ventilators/bring health care providers out of retirement [Health system capacity] ‘Defence in depth’ • Combinations of measures will often be more effective than single measures  so‐called ‘defence in depth’ or ‘layered interventions’ – or the ‘Swiss cheese’ analogy = no single layer (of “cheese”) is perfect IE each has “holes”, and when the holes align, the risk of infection increases BUT having several layers combined means that the holes in the cheese are less likely to align and the pathogen will not be able to slip through. • Combining measures may increase protection but will inevitably increase their overall cost. Measures range from relatively straightforward to implement (e.g. hand washing) to costly and potentially highly disruptive (e.g. border closures). Summary Today we have: • Described the key concepts in communicable disease control • Described the key measures in infectious disease surveillance and outbreak control • Defined infectious disease emergencies and explored options for managing these events