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Introduction to Public Health Surveillance Tunisia, 28th October 2014 Dr Gordana Kuzmanovska National Public Health Institute, The former Yugoslav Republic of Macedonia [email protected] Learning Objectives • What is surveillance? • Public health/epidemiological surveillance • Purposes and uses of public health surveillance • Data sources • Components of public health surveillance • Types of surveillance What is surveillance? Could you drive without looking at the traffic? Can you make public health decisions in the absence of data? Definition ”Surveillance is the ongoing process of systematic collection, collation, analysis and interpretation of data; than dissemination of information to those who need to know (feedback ) in order that action may be taken” World Health Assembly 2005 (modificated) Surveillance is information for action! “Good surveillance does not necessarily ensure the making of the right decisions, BUT it reduces the chances of [making the] wrong ones.” Alex Langmuir, 1963 Purposes of public health surveillance • Assess public health status • Define public health priorities • Evaluate existing programs • Trigger public health action • Stimulate research Surveillance objectives Surveillance should be SMART... S - Specific (regarding event which is subject of ) M - Measurable (gain info for comparison ) A - Action oriented (information for action) R - Realistic & (feasible in time and place) T - Timely (action implemented in time to be effective) Setting objectives – balance between requirements and interests! Characteristics (attributes) of surveillance system • • • • • • • • Simplicity Flexibility Acceptability Sensitivity Positive predictive value Representativeness Timeliness Usefulness Uses of public health surveillance • • • • • • • Detection of sudden changes in disease occurrence and distribution Monitoring trends and patterns Detection of changes in health practices Monitoring changes in infectious agents Evaluation of control measures Provide an evidence base for policy and guidance formulation Generate hypotheses, stimulate research Surveillance components The surveillance loop Health care system Surveillance centre Data Event Planning, Evaluation, Policy formulation Action Information Feedback, recommendations Analysis, interpretation Reporting Event and population under Surveillance EVENT • Disease • Syndrome – Acute flaccid paralysis – Influenza-like illness – Diarrhoea • Infection POPULATION AND TIME • Everyone – country, region, city • Patients in hospitals • Employees in a factory • Public health issue – Antimicrobial resistance • Environment – Vector population – Water quality • All children in the winter months? The surveillance loop Health care system Reporting Data Planning, Evaluation, Policy formulation Action Information Feedback, recommendations Analysis, interpretation Event Surveillance centre Surveillance methods key data items collected Numerators – number of cases of disease – antibody positive samples – number of resistant strains Descriptors – characteristics of patients, strains, etc. Denominators – total population at risk in a given time frame – total number of strains examined – or sub-sample Case definition YES NO - A “case” is an event - A “case” is not a person - An event is something that happens to: - Events do not exist if you lack info: • A person, o On the person • In a given place, o On the place • At a given time o On the onset date - A case definition is a set of criteria that triggers reporting - A case definition is not a diagnosis made to decide treatment Case definition (ii) Includes: Should be: Time, place, person. Clear, simple Clinical features Field tested and /or Laboratory results and/or Epidemiological features Stable and valid Adopted Case definition (iii) Meningococcal disease (SURVEILLANCE PURPOSES) Possible case Clinical diagnosis of meningitis or septicaemia or other invasive disease where the CCDC/CPH, in consultation with the clinician and microbiologist, considers that diagnoses other than meningococcal disease are at least as likely Probable case Clinical diagnosis of meningitis or septicaemia or other invasive disease where the CCDC/CPH, in consultation with the physician and microbiologist, considers that meningococcal infection is the most likely diagnosis Confirmed case Clinical diagnosis of meningitis, septicaemia or other invasive disease AND at least one of: • Neisseria meningitidis isolated from normally sterile site • Gram negative diplococci in normally sterile site • Meningococcal DNA in normally sterile site • Meningococcal antigen in blood, CSF or urine. Case definition (iv) Ebola case-classification criteria (OUTBREAK INVESTIGATION) Suspected (possible) case Any person, alive or dead, who has (or had) sudden onset of high fever and had contact with a suspected, probable or confirmed Ebola case, or a dead or sick animal OR any person with sudden onset of high fever and at least three of the following symptoms: headache, vomiting, anorexia/loss of appetite, diarrhea, lethargy, stomach pain, aching muscles or joints, difficulty swallowing, breathing difficulties, or hiccup; or any person with unexplained bleeding OR any sudden, unexplained death. Probable case Any suspected case evaluated by a clinician OR any person who died from ‘suspected’ Ebola and had an epidemiological link to a confirmed case but was not tested and did not have laboratory confirmation of the disease. Confirmed case A probable or suspected case is classified as confirmed when a sample from that person tests positive for Ebola virus in the laboratory. Reporting (data transfer) • Data transfer method – Paper by post – Telephone – E-mail – Secure Internet (web based) • Data transfer frequency – For every case – Daily – Weekly – Quarterly Reporting (data transfer) • Individual data – Identified – name, personal id number – Non-identified – but possible to trace back. – Anonymous – impossible to trace back • Aggregated data – Numbers – Tabulated numbers – by sex, age group etc. The surveillance loop Health care system Surveillance centre Event Data Planning, Evaluation, Policy formulation Action Information Feedback, recommendations Analysis, interpretation Reporting Data Sources • • • • • • • • Notifications of infectious diseases Microbiology laboratory reports Sentinel surveillance Hospital records / primary health care records Registries Screening programmes (antenatal, blood donors) Prescriptions / over the counter drug sales Surveys Non medical data sources: • • • • Populacion statistics (vital statistic records-birth registration) Veterinary surveillance, Vectors (Wild and domestic animals Environmental (food, water, air sampling) Media (internet, newspapers, TV) The surveillance loop Health care system Surveillance centre Data Event Planning, Evaluation, Policy formulation Action Information Feedback, recommendations Analysis, interpretation Reporting Analysis of surveillance data Data analyzing according to time-place-person! Descriptive use Measures of disease frequency: • Incidence: no. cases/population at risk over given time period – 5 cases per 1000 person years; 0.3 cases per 1000 bed-days • Prevalence : no. cases/population at risk at a set time – 15% of patients sampled antibody positive; – 3% strains erythromycin resistant Analysis of surveillance data (ii) Analytical use • Comparison between groups to gain a measure of increased risk - e.g. case fatality in males vs. females - e.g. change in rate of infection over time • Analytic methods Time-series analyses to detect aberrations Time-space clustering Interpretation: What accounts for increased cases? • • • • • • • • Changes in reporting procedure or surveillance system Changes in case definition Improvements in diagnostic procedures / new lab testing Improved access to health care Increased awareness (doctors), health seeking behavior (patients) Changed circumstances - new physician/new clinic – may see more referred cases, make diagnosis more often, report more consistently, more responsible Laboratory or diagnostic error OR A true increase in incidence Figure 5.7 Reported Cases of Salmonellosis per 100,000 Population, By Year — United States, 1972–2002 Figure 5.8 Reported Cases of AIDS, by Year — United States* and U.S. Territories, 1982–2002 Source: Centers for Disease Control and Prevention. Summary of notifiable diseases–United States, 2002. Published April 30, 2004, for MMWR 2002;51(No. 53): p. 59. •Total number of AIDS cases includes all cases reported to CDC as of December 31, 2002. Total includes cases among residents in the U.S. territories and 94 cases among persons with unknown state of residence. Source: Centers for Disease Conrol and Prevention. Summary of notifiable diseases–United States, 2002. Published April 30, 2004, for MMWR 2002;51(No. 53): p. 59. The surveillance loop Health care system Surveillance centre Event Data Planning, Evaluation, Policy formulation Action Information Feedback, recommendations Analysis, interpretation Reporting Dissemination of Surveillance Data • Dissemination should be “Up and Down” – Surveillance summaries / reports – Health agency newsletter (Epi Bulletin) – Medical / epidemiologic journal articles – Press releases (web) The surveillance loop Health care system Surveillance centre Event Data Planning, Evaluation, Policy formulation Action Information Feedback, recommendations Analysis, interpretation Reporting Surveillance is information for action! Uses of public health surveillance • • • • • • • Detect sudden changes in disease occurrence and distribution (outbreaks & emerging epidemics) Monitor trends and patterns Detect changes in health practices Monitor changes in infectious agents Evaluate control measures Provide an evidence base for policy and guidance formulation Generate hypotheses, stimulate research Reported diarrhea cases by week, East Amman, Jordan 1995-2000 Can you see an outbreak of disease? Reported diarrhoea cases by week, East Amman, Jordan 1995-2000 (ii) Here it is the outbreak! Registered influenza cases in R. of Macedonia in the epidemic years 2009-2010, by weeks Uses of public health surveillance • • • • • • • Detect sudden changes in disease occurrence and distribution Monitor trends and patterns, prediction of outbreak Detect changes in health practices Monitor changes in infectious agents Evaluate control measures Provide an evidence base for policy and guidance formulation Generate hypotheses, stimulate research Registered HIV/AIDS cases and deaths in the former Yugoslav Republic of Macedonia, by years (1989-2013) 30 Cases 25 Deaths 20 15 10 5 0 HIV+ tested TB patients received CPT and ART, 2003-2010 Source: World Health Organisation. Collaborative TB/HIV activities, 2010 Estimated number of adults and children living with HIV in former Yugoslav Republic of Macedonia by 2015 Uses of public health surveillance • • • • • • • Detect sudden changes in disease occurrence and distribution Monitor trends and patterns Detect changes in health practices/monitoring progress Monitor changes in infectious agents Evaluate control measures Provide an evidence base for policy and guidance formulation Generate hypotheses, stimulate research ile B A bd om liv er ia lh ys or te C pa or re on nc ct om re ar at y y A ic rte su ry rg B er yp y as s G G as ra To tri ft c ta su lh rg ip er re y H p ip la ce he m m en ia t rth K r op ne la e st re y La pl ac rg em e bo en w t el s Li O ur m pe ge b n ry a re m du pu ct ta io tio n n S of m f al ra lb ct ur ow e el su V as rg cu er y la rs ur ge ry du ct , Distribution of surgical site infection by category of surgical procedure, Oct 1997 - Dec 2003 25 20 15 10 5 0 Uses of public health surveillance • • • • • • • Detect sudden changes in disease occurrence and distribution Monitor trends and patterns Monitor/detect changes in health practices Monitor changes in infectious agents (Outbreak predicting?) Evaluate control measures Portray the natural history of a disease Generate hypotheses, stimulate research number of reports Staphylococcus aureus bacteraemia reports and methicillin susceptibility, England & Wales 17,500 resistant 15,000 12,500 10,000 7,500 5,000 2,500 0 no information sensitive Uses of public health surveillance • • • • • • • Detect sudden changes in disease occurrence and distribution Monitor trends and patterns Monitor/detect changes in health practices Monitor changes in infectious agents Evaluate prevention and control measures (effectiveness of intervention) Provide an evidence base for policy and guidance formulation Generate hypotheses, stimulate research Measles/rubella incidence in Macedonia and immunization schedule changes in the period 1967-1997 600 500 МB/100.000 400 300 200 100 0 1972 M vaccine (13 months) Measles Rubella 1983 МMR vaccine (13 months) 1987 М revaccine (7 years) R revaccine (14 years 1997 МMR revaccine (7 years) Uses of public health surveillance • • • • • • • Detection of sudden changes in disease occurrence and distribution Monitoring trends and patterns Monitoring/detect changes in health practices Monitoring changes in infectious agents Evaluation of prevention and control measures Provide an evidence base for policy and guidance formulation – future action Generate hypotheses, stimulate research MMR vaccination coverage in 1983-2007 and mumps case distribution in 2007-2009, by year of birth 100 1238 1200 95 1100 90 85 900 Број на заболени 922 814 % Опфат со МР(П) вакцина 75 800 700 600 80 70 697 538 % Опфат со МР(П) ревакцина 500 65 60 55 400 50 300 45 200 40 100 35 0 30 Year of birth Institute of Public Health Vaccination coverage % 1000 19781979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Number of mumps cases 1300 HIV transmision – corelation between heterosexual and homosexual (MSM ) 1987 - 2011 18 16 14 heterosexual cases 12 MSM cases 10 8 6 4 2 0 Uses of public health surveillance • • • • • • • Detect sudden changes in disease occurrence and distribution Monitor trends and patterns Monitor/detect changes in health practices Monitor changes in infectious agents Evaluate prevention and control measures Provide an evidence base for policy and guidance formulation Generate hypotheses, stimulate research MRSA bacteriemia in children proposal to undertake enhanced surveillance of MRSA in children !!! Remember…. Surveillance is information for action! Types of Surveillance • Passive surveillance – Routine reporting through the normal channel • Stimulated passive surveillance – Routine reporting through the normal channel following a special request / stimulus • Active surveillance – Public health staff actively seek cases • Population, specific groups • Health care facilities Passive Surveillance • Health care facilities or providers report cases as they present to health care facilities • No specific efforts are made to ensure that all cases are reported • Surveillance is integrated into routine health care delivery system (mandatory reporting) • Advantages: The most often in use, routine, long-term trends • Disadvantages: • Missing data, lack of motivation, low quality, robust Stimulated Passive Surveillance • Health care facilities or providers report cases as they present to health care facilities • Surveillance remains integrated into routine health care delivery (zero reporting) • Special efforts are made to maximize reporting – Reminders, visits, guidelines • Example: Surveillance of AFP Active Surveillance • The system does not wait for: – Patients to come to health care facilities • Health care workers actively reach out to detect cases (daily, weekly) • Surveillance is in addition to the routine health care delivery • Early detection, timely prevention ... • Resource intensive (time consuming, cost) Sentinel Surveillance • Reporting of health events by selected health professionals (GP, hospitals) • Chosen health care facilities report cases – Sentinel sites: representing a certain geographic area (city, region) or a specific reporting group (children...) • Can be active or passive surveillance • The surveillance system only captures events in selected areas. Sentinel Surveillance • Advantages − Rationale – less but better data − Consistent data – stable sample − Choice of sentinel sites (motivation, responsibility, competency, data quality, geographical distribution, timelines) • Disadvantages − − − − Representativeness? Voluntary principe Denominator? Actors rotation Motivation lost Syndromic Surveillance • Syndrome is a complex of symptoms • Syndromic surveillance focuses on one symptom or constellation of symptoms (clinical outcomes) rather than a diagnosed disease • No need of laboratory confirmation. Hence fast. • More sensitive, but less specific • Faster public health interventions We see only the tip… "see what we look for!" Reported + specimen ve Lab-based surveillance Clinical specimen Seek medical attention Serological surveys Clinical Disease Infected Exposed Syndromic Surveillance Key messages • Remember: • Surveillance is information for action! • Good surveillance always influences decisions in the right direction!!! Thank you! Dr Gordana Kuzmanovska National Public Health Institute, The former Yugoslav Republic of Macedonia [email protected]