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Edit Comment Close Premium member Presentation Transcript EPIDEMIOLOGICAL SURVEILLANCE AND DIFFERENT METHODS OF SURVEILLANCE: EPIDEMIOLOGICAL SURVEILLANCE AND DIFFERENT METHODS OF SURVEILLANCE DR AJAY TYAGI JR,DEPTT. OF COMMUNITY MEDICINE PGIMS,ROHTAKContent: Content Introduction Definition Purpose of surveillance Characteristics of surveillance Uses of surveillance Components of (public health) surveillance Why do we do public health surveillance? Prerequisite for effective surveillanceIntroduction: Introduction Surveillance is the continuous watch over the behaviour, activities , or other changing information, usually of people and often in a surreptitious manner . All outbreaks cannot be predicted or prevented. However, precautionary measures can be taken within the existing health infrastructure and service delivery to reduce risks of outbreaks and to minimize the scale of the outbreak, if it occurs.Introduction: Introduction The alertness for identification of early warning signals and the capacity for initiating recommended specific i nterventions in a timely manner is surveillance While the concept of surveillance in epidemiology goes back centuries—at least to Graunt and Farr —the practice of surveillance continues to evolve.Introduction: Introduction Its most important modern milestone was the clear and precise definition given to this practice by Langmuir in 1963. He stated that surveillance i s “the continued watchfulness over the distribution and trends of occurrence through the systematic collection , consolidation, and evaluation of morbidity and mortality reports and other relevant data”Introduction: Introduction DEFINITION Surveillance is defined as the ongoing systematic collection, collation, analysis, and interpretation of data and dissemination of information to those who need to know in order that action is taken. The final link in the surveillance chain is the application of these data to prevention and controlIntroduction: Introduction Surveillance is the backbone of public health programme and provides information so that effective action can be taken in controlling and preventing diseases of public health importance In some cases action must be immediate – within hours – in order to prevent large scale epidemics and deaths (Cholera, meningitis, food contamination).Introduction: Introduction In others, control and prevention activities are long term response to information about disease such as tuberculosis, HIV and Non Communicable Disease risk factors, for which action may be taken in weeks, months or even years.Purpose : Purpose In the practice of epidemiology and public health, surveillance has the following three generic purposes: ( a) surveillance may identify public health problems , ( b) surveillance may stimulate public health intervention , and ( c) surveillance may suggest hypotheses for epidemiological research .Characteristics of a Surveillance System : Characteristics of a Surveillance System An effective system of public health surveillance has following essential attributes : 1. Simplicity 2 . Acceptability 3. Sensitivity 4. FlexibilityCharacteristics of a Surveillance System : Characteristics of a Surveillance System 5. Data quality 6 . High predictive value positive (PVP) 7 . Timeliness 8. Stability 9. RepresentativenessCharacteristics of a Surveillance System : Characteristics of a Surveillance System ♦ Simplicity Is the system simple in structure and easy to operate? Are there steps in the process that could be combined or eliminated? Surveillance systems should be as simple as possible while still meeting their objectives. The simpler the system, the more acceptable and timely it is likely to be. Simpler systems also take fewer resources to operate .Characteristics of a Surveillance System : Characteristics of a Surveillance System ♦ Flexibility Can the system adapt to changing information needs or operating conditions with little additional time, personnel, or allocated funds? Does the system use standard data formats (e.g., in electronic data interchange) that can be easily integrated with other systems ?Characteristics of a Surveillance System : Characteristics of a Surveillance System ♦ Data quality Is the information in the system complete and valid? One easy way to check this is to examine the percentage of "unknown" or "blank“ responses to items on surveillance forms. However, a full assessment might require a special study in some cases.Characteristics of a Surveillance System: Characteristics of a Surveillance System ♦ Acceptability Are people and organizations willing to participate in the surveillance system ? ♦ Sensitivity What proportion of actual cases are detected by the surveillance system? Can the system monitor changes in the numbers over time, and detect outbreaks?Characteristics of a Surveillance System: Characteristics of a Surveillance System ♦ Predictive value positive What proportion of reported cases actually have the disease under surveillance ? This can be assessed by looking at how many of the reported cases meet the case definition, or how many are eventually classified as confirmed. ♦ Representativeness Does the system accurately describe the occurrence of the disease over time and its distribution in the population by place and person? Or is it “skewed” toward certain age groups, ethnic groups, geographic areas, or healthcare providers?Characteristics of a Surveillance System: Characteristics of a Surveillance System ♦ Timeliness How quickly does the system receive and process information? This can be assessed by looking at the speed between steps in the system. ♦ Stability How reliable is the system (reliability is the ability to collect, manage, and provide data properly without failure). Is the system operational when it is needed? Uses of Surveillance : Uses of Surveillance Assess the public health impact of health events and determine their trends Recognize cases or cluster of cases to trigger interventions to prevent transmission or reduce morbidity and mortality Demonstrate the need for public health intervention programs and resources and allocate resources during public health planning Monitor effectiveness of prevention and control measures Identify high-risk groups or geographical areas to target interventions and guide analytic studies Develop hypothesis that lead to analytic studies about risk factors for disease causation , propagation or progression.COMPONENTS OF (PUBLIC HEALTH) SURVEILLANCE : COMPONENTS OF (PUBLIC HEALTH) SURVEILLANCE Our definition of surveillance consists of five components: 1. Ongoing, systematic collection of health data 2. Data analysis 3. Interpretation of data, 4. Dissemination of the information, AND 5. Linking the data to public health practice 1 Methods of data collection: 1 Methods of data collection Several methods can be used for collecting data. While routine reporting ( passive surveillance) is universalized , other methods are need and area specific. These include: Sentinel surveillance Active surveillance (active search for cases) Vector surveillance Laboratory surveillance Sample surveys Outbreak investigations Special studiesPASSIVE SURVEILLANCE: PASSIVE SURVEILLANCE Routine reporting (institutional based or reporting ) All the national health programmes require that the cases and deaths recorded in the outpatient or in-patient departments of hospitals, dispensaries, CHC, PHC and other health facilities manned by a medical officer are reported to the local health authority on a monthly basis. In the Integrated Disease Surveillance Program the essential surveillance components will be identified and transfer of information to program officers facilitated so that information for action is available on a weekly basis.PASSIVE SURVEILLANCE: PASSIVE SURVEILLANCE At each level in the system, the report is required to be analyzed and appropriate action taken as indicated. The reports should be checked for completeness and regularity as these factors can influence the analysis of the reports .Active surveillance : Active surveillance However good the routine reporting system, there will still be cases that will not be recorded under this system. Patients with mild or moderate severity may not seek treatment and some may go to private practitioners. It is also possible that patients in severe condition are taken directly to a large hospital in another district for specialized care. Some cases may die within a short period of onset of symptoms without receiving care at a health facility such as cases of neonatal tetanus.Active surveillance : Active surveillance Active surveillance or active search for cases is resource intensive. The decision to start active surveillance depends on many factors and ground situations. Active search may be called for under the following circumstances. During outbreaks, determine the extent of the outbreak and keep mortality rates low by initiating early treatment. Active surveillance is carried out to know the magnitude of the problem which will help in planning logistics for control.Active surveillance : Active surveillance In addition, it will give baseline data to evaluate control strategy. It also helps in understanding the genesis of the outbreak. To check if reports received by rumor registry are true. As the number of cases of a disease decline to negligible levels, it becomes important to receive information on every single case as quickly as possible so that further transmission is interrupted by initiating outbreak control measures.Active surveillance : Active surveillance For example, active surveillance is recommended for Acute Flaccid Paralysis (AFP)To confirm the absence of even a single case . This is done during the pre-certification phase for disease eradication, as ‘zero’ incidence has to be maintained for a period of three years. During field visits by the supervisors, absence of disease can be confirmed by contacting few key persons such as a school teacher, gram pradhan , anganwadi worker and others.Active surveillance : Active surveillance The health personnel, outreach personnel of other government departments, non-governmental organizations, panchayats and the members of the community must be encouraged to report cases. The case definition of the disease should be widely circulated for this purpose. The health personnel should not be punished or discouraged in any way from reporting cases as this will lead to suppression of vital information.Sentinel surveillance : Sentinel surveillance A sentinel surveillance system is developed to obtain more reliable and extensive disease related information than the one that is available through the routine reporting. A hospital, health center, laboratory or a rehabilitation center which caters to a relatively large number of cases of the disease can be considered as a sentinel center. A sentinel center can provide information on one or more diseases. Since the sentinel centers are carefully selected and because the number of the reporting units is much smaller, it is easier to maintain the quality and regularity of the reports .Sentinel surveillance : Sentinel surveillance There should be a close liaison between the sentinel center and the local health authorities. The sentinel from the private sector can help in providing early warning signals, which should trigger action for outbreak investigation. The sentinel center data will not include all cases in the area. However, if one or more sentinel centers have been carefully selected, it will include sufficiently large number of cases for epidemiological analysis.Sentinel surveillance : Sentinel surveillance Data from sentinel centers are useful to determine trends in the incidence of the reported disease. The district hospital, infectious diseases hospital, medical college hospital (if located in the district ) and other large hospitals and laboratories should be included as sentinel centers and reports from these centers should be analyzed separately. These centers would also be submitting the routine monthly report under the passive surveillance system .Laboratory Surveillance : Laboratory Surveillance Laboratory surveillance plays an important part in confirming diseases since regular summary data can at best be presumptive. The validity of changing trends in suspect cases ( syndromes) and presumed cases made by Medical Officers can be confirmed only by laboratory testing. Under IDSP, the laboratory network will report independently all confirmed cases in a prescribed format. This will allow to understand and validate the changes in pattern of syndromes and probable cases seen at the reporting centers.Laboratory Surveillance : Laboratory Surveillance Laboratories also help in diagnosis of cases for case management and this function will be facilitated by quick feed back of laboratory reports on a case based format back to the reporting units. Clinical samples should be collected and transported properly to the identified laboratories for appropriate tests. The samples should be labeled properly and accompanied with requisite epidemiological information. Testing water samples for coliform organisms is a measure to determine the risk of water borne outbreaks.Laboratory Surveillance : Laboratory Surveillance Water quality monitoring is recommended in vulnerable pockets and from sources supplying drinking water to a large population. Checking the chlorination levels of the water is also important, especially during the monsoon and post-monsoon periods. These measures by the health department are precautionary measures in addition to the mandatory requirements of the concerned department.Laboratory Surveillance : Laboratory Surveillance Laboratory surveillance must be stepped up in anticipation or in the event of an outbreak. Serological and other laboratory based surveys are sometimes conducted as research projects to collect baseline prevalence rates or to identify high risk factors, age-groups or population sub-groups. The identification of new agents and changes in the behavior of micro-organisms especially in relation to susceptibility to anti- microbials are also important components of laboratory surveillance.Sample surveys : Sample surveys Surveys give reliable epidemiological information. These are particularly useful to collect baseline data prior to the launch of a large control program, especially if such data are lacking through other sources. In IDSP Non communicable diseases (NCD) risk factors will be collected through regular surveys. The sample size, sampling procedure, methodology, questionnaires and forms must be well designed to avoid bias and misinterpretation of data. These surveys can be conducted after a period of 3 to 5 years cyclically.Special Studies : Special Studies Special studies are sometimes required to study problems that are not addressed through the methods of data collection listed above. Some districts, for example, may have a high prevalence of cases linked to or suspected to be due to environmental pollution; other districts may have problems related to multi-drug resistant micro-organisms.Outbreak Investigations : Outbreak Investigations Outbreak investigation is the primary method of confirming emerging infections. Changes in trends observed and suspected outbreaks are confirmed by outbreak investigations. Outbreaks investigations provide a rich source of epidemiological information. The outbreaks should be investigated to ascertain its etiology and understand why they occurred as well as to identify high risk areas and groups.Outbreak Investigations : Outbreak Investigations Laboratory help should be utilized in establishing the diagnosis of early cases only. Once the cause of outbreak is confirmed, laboratory support should not be wasted for each and every case. The data collected as a result of outbreak investigations must be utilized for improving programme activities and the surveillance system as well as for filling gaps identified as a result of these investigations. The results should be shared with other district officers and other states so that the experience gained could be effectively used for preventing such outbreaks in these areas.2. DATA ANALYSIS: 2. DATA ANALYSIS Before surveillance data can be interpreted, they must be organized and analyzed. Computer systems are frequently used to compile the information and analyze it. We must always take care to clearly define the questions we are trying to answer through data analysis, to make sure the results are useful for public health action. In some circumstances, for example the very early stages of investigating a suspected outbreak, hand tallies of information about suspected cases may be useful.2. DATA ANALYSIS: 2. DATA ANALYSIS A. Determine the number of cases. Every reportable disease has an official case definition that is used to determine whether a case should be “counted” in the surveillance system. The case definition is usually a combination of symptoms and laboratory test results, and is defined by CDC for nationally notifiable diseases. Case definitions reflect different levels of certainty. There are definitions for suspect vs. probable vs. confirmed cases . Each case reported to the system should be evaluated in relation to the case definition, as a basic quality assurance mechanism.2. DATA ANALYSIS: 2. DATA ANALYSIS B. Calculate incidence rates. Rates take into account the size of the population so comparisons can be made across geographic areas. By using rates, the incidence in one county can be compared to state or national incidence of the disease.2. DATA ANALYSIS: 2. DATA ANALYSIS C . Analyze the data by person, place and time. Person includes variables such as age, sex, and race, as well as risk factors such as childcare or food handler status. Place may be a nation, state, county, city or even zip code or census tract. Time is usually represented as date of onset of illness, grouped by day, week , month or year.2. DATA ANALYSIS: 2. DATA ANALYSIS D. Current surveillance data are compared with some expected value to identify how they differ and to assess their importance. One way to do this is by comparing the incidence rate in the current time period with past incidence in the same jurisdiction. This may be incidence as of the same time last year, or a measure of the “usual” incidence, such as a five-year median2. DATA ANALYSIS: 2. DATA ANALYSIS E. It is also useful to compare with other jurisdictions. Is the current incidence rate in County A significantly higher than that in surrounding counties, or the state or national average? If so, that may indicate a problem that needs to be followed up. F . Spatial analysis may be helpful. Modern technology such as Geographic Information Systems (GIS) can create very informative analyses. The locations of cases can be viewed in relation to environmental features and/or population characteristics .3. INTERPRETATION OF DATA: 3. INTERPRETATION OF DATA If the analysis shows that the incidence of a disease is different from what you would expect , then further investigation should be done. For some diseases, this is true even if the number of cases is small. Example: even a single case of a potential bioterrorist agent (such as anthrax ) or a vaccine-preventable disease (such as measles) should be investigated. There are several possible explanations for changes in surveillance data.3. INTERPRETATION OF DATA: 3. INTERPRETATION OF DATA Explanations that should be considered include (but are not limited to ): An outbreak An intentional exposure (such as a bioterrorist attack) A newly emerging infection Improved diagnosis (new laboratory test, increased physician awareness) Increased awareness of the disease and/or the need to report it3. INTERPRETATION OF DATA: 3. INTERPRETATION OF DATA A gradual increase or decrease in incidence due to environmental or population changes, or changes in the disease agent A disease following its natural seasonal or “secular” (years-long) cycle Changes in the surveillance system (new data collection system, loss of a reporting source, addition of a new source, change in case definition, etc.)4. DISSEMINATION OF THE INFORMATION: 4. DISSEMINATION OF THE INFORMATION Sharing the Results The purpose of sharing surveillance information is to inform those who need to know, and to motivate those who need to do something. Examples: keeping healthcare providers informed about current trends can help them diagnose and treat their patients better. Keeping policymakers informed can assist them in allocating resources and updating rules, ordinances and laws. And keeping public health professionals and administrators up to date will help them design and carry out better programs.4. DISSEMINATION OF THE INFORMATION: 4. DISSEMINATION OF THE INFORMATION Surveillance data generally flow “up” through the public health system, from local reporters to local public health agencies, to DGHS, to NCDC , to the World Health Organization (WHO ). As with any good communication, the information must be tailored to the audience. Public health workers may need more detailed information than other groups. In general, reports should be brief and clear, and should highlight the information most important to the reader.5. LINKS TO PUBLIC HEALTH PRACTICE: 5. LINKS TO PUBLIC HEALTH PRACTICE Information for Action The only reason to carry out public health surveillance is to use the information to improve the health of the public. “ Why Do We Do Public Health Surveillance?”WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? A well-designed surveillance system can provide critical information for public health action. Agencies use various kinds of surveillance data to: 1 . Guiding immediate action for cases of public health importance . A good surveillance system serves as an “early warning” system for the community’s health. When an unusual disease case occurs, the public health agency can investigate immediately and implement control measures if needed to prevent spread.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE ? For example, even a single case of anthrax, measles or diphtheria should trigger a full-scale public health investigation . 2 . Describing and monitoring health events and trends through surveillance systems can allow us to : Detect sudden changes in disease occurrence and distribution. We may notice a sudden increase that could be an outbreak. Or a disease that previously occurred mainly in one group of people may move to another Follow long-term trends and patterns of disease .WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? Many diseases ebb and flow in cycles that vary by season or over several years. Knowing this may help us interpret the current situation. Identify changes in agents and host factors. Many infectious agents change over time. (E.g., shifts in predominant salmonella serotype by year, antibiotic resistant gonorrhea]. Data from laboratory scientists who monitor these characteristics can be used to direct vaccine production, treatment, and other prevention and control measures.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? 3. Set priorities for the use of resources . Surveillance data are very important in determining the best use of a public health agency’s time, staff and budget. Which diseases or conditions have the greatest impact on the population? Infectious disease trends may change quickly, sometimes even overnight, and health agency resources must be flexible to respond effectively.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? Example : a suspected bioterrorism incident or an outbreak of foodborne illness may supersede other routine activities. In such a situation, staff must be reassigned to: intensify surveillance to identify other susceptible and potentially exposed people search for the source of the problem design and implement control measures (environmental controls, screening, immunization and/or treatment, restriction of activities)WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? If the outbreak is large, or the disease very serious, the agency’s emergency response plan may need to be activated In that case many resources outside the agency can be brought into play. Surveillance data can also be used to identify when a public health problem has been solved, so that resources can be redirected to other, more pressing needs. However, if this is done too soon, the consequences can be costly . Example : it may be tempting to cut resources for tuberculosis control when the incidence goes down. This was one in the 1980s, and the result was an upsurge in tuberculosis cases.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? 4. Assist in planning, implementing and evaluating public health interventions and programs . Information from ongoing surveillance systems helps us identify public health problems and design programs to address them. In the planning stage, surveillance can pinpoint where a problem is occurring and who is affected by it so that efforts can be directed to the right area and the right people. In the implementation stage, good data can help persuade policymakers and community members that a program or policy change is needed and worth supporting.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? In the evaluation stage, surveillance data can help us determine the effect of our efforts. If the program or intervention is working, then disease incidence should go down. EXAMPLES a. When surveillance data showed that a new A rbovirus , the West Nile Virus, was spreading across the country, public health agencies developed plans to prevent and control it. They tried several new approaches including :WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? Public education campaigns (billboards, radio spots) to promote the use of mosquito protections, including DEET insect repellent Public education and code enforcement activities to reduce mosquito breeding sites by emptying/draining standing water Community cleanup activities to reduce mosquito habitat Agencies then evaluated the results of these efforts through surveys as well as by continued, intensive surveillance activities.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? B. Detailed surveillance data regarding HIV infection have guided community planning for prevention programs. In the 1980s when aids first emerged, health education messages were targeted toward the groups most heavily impacted by the epidemic, men who have sex with men and injecting drug users. In the late 1990s, the data showed that HIV was beginning to infect more women, especially minority women. Outreach and education programs were designed to reach out to women, for example, by distributing gender and culture-appropriate materials in places where women go, such as beauty shops.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? 5. Evaluate Public Policy Public policies, such as laws, ordinances, and institutional policies, are important public health interventions. Surveillance information can help identify needed policy changes. EXAMPLES a. Immunization requirements have evolved as disease transmission patterns change. School immunization rules were implemented and enforced to reduce outbreaks of measles and rubella in schools.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? As more children entered childcare centers and homes, the transmission of vaccine-preventable diseases among preschool children increased. In the 1980s, immunization requirements for childcare attendance were developed and incorporated into licensed requirements. Outbreaks in licensed childcare settings have since become rare.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? b . Standards for food protection are codified as state rules and local ordinances. Inadequacies in these food codes were identified in the 1990s through surveillance data, and the rules were strengthened. Required cooking temperatures for beef were changed because of E. coli O157:H7 outbreaks. The rules on the transport and handling of fresh eggs were changed because of outbreaks of Salmonella enteritidis .WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? 6 . Generate questions and hypotheses that provide direction for further research. Surveillance data by themselves cannot answer questions about the causes of illness. However , observation of the patterns of disease can help generate ideas about causes and potential control measures. These ideas can be developed into research hypotheses that lead to new knowledge in disease prevention and control.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? EXAMPLES a. Toxic shock syndrome ( TSS) is a serious illness caused by certain toxin-producing strains of the Staphylococcus aureus bacterium. It usually has a sudden onset of fever, chills, vomiting , diarrhea, muscle aches and rash, and can rapidly progress to multisystem dysfunction. About 5% of cases are fatal. An epidemic of TSS in women of childbearing age was detected through public health surveillance in the late 1970s.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? Menstruating women and women using barrier contraceptives such as intra-uterine devices (IUDs) were at highest risk. This observation led to further research on tampons, which found that the fibers used in certain highly absorbent brands encouraged bacterial growth. These brands were removed from the market, the epidemic abated, and TSS incidence has declined ever since.WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? : WHY DO WE DO PUBLIC HEALTH SURVEILLANCE? b . Vaccine policies may be adjusted as a result of research prompted by surveillance findings. A puzzling upsurge in measles cases occurred in the late 1980s, in Missouri and throughout the US, mainly in school-age children. This upsurge prompted CDC to study the children’s antibody levels, and they found that immunity waned among those who had only one measles shot. Two doses of measles vaccine have been required for school attendance since that time in US.Prerequisite For Effective Surveillance: Prerequisite For Effective Surveillance Prerequisite for effective surveillance are: Use of standard case definitions Ensure regularity of the reports Action on the reportsCASE DEFINITIONS: CASE DEFINITIONS A case definition is the method by which public health professionals define who is included as a case in an outbreak investigation, (i.e. a person considered directly affected by an outbreak) or in the surveillance of public health conditions . A case definition has the following characteristics , it defines a case in time, person and place . Time criteria may include all cases of a disease identified from, for example, January 1, 2008 to March 1, 2008. Person criteria may include age, gender, ethnicity, and clinical characteristics such as symptoms (e.g. cough and fever), clinical tests (e.g. pneumonia on chest X-ray ).CASE DEFINITIONS: CASE DEFINITIONS Place criteria will usually include a geographical entity such as a town, state, or country but may be as small as an institution, a school class, or a restaurant meal session. Case definitions may also be categorised into suspect, probable and confirmed cases. For example in the investigation of an outbreak of pneumococcal pneumonia in a nursing home the case definition may be specified as: Suspect Case: All residents of Nursing Home A with onset of cough and fever between January 1, 2008 and February 1, 2008 .CASE DEFINITIONS: CASE DEFINITIONS Probable Case: Meet the suspect case definition plus have pneumonia on chest X-ray. Confirmed Case: Meet the probable case definition plus have pneumococcal infection confirmed by blood culture or other isolation of pneumococci from normally sterile site. By creating a case definition, public health professionals are better equipped to study an outbreak and determine possible causes. As investigations proceed, this definition may be expanded or narrowed. This is characteristic of the dynamic nature of outbreak investigations. Surveillance Must Involve : Surveillance Must Involve To be effective, surveillance systems must involve Public health agencies, Healthcare providers, and The public Active cooperation is essential so that accurate , timely information can be collected and acted uponPowerPoint Presentation: There is no value to surveillance system unless the information is used for action that prevent or control diseasesReferences: References IDSP Medical Officers Manual A Dictionary Of Epidemiology Maxcy - rosenau -last Internet You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.