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INPPAZ - PAHO - WHO GuiaVETA |
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CHAPTER I 1. GENERAL CONSIDERATIONS The present Guidelines for the Establishment of Epidemiological Surveillance. Systems for Food-Borne Diseases (FBD) and the Investigation of Outbreaks of Food Poisonings is an updated version of the previous publication, Guidelines for the Establishment of Systems for the Epidemiological Surveillance of Food-borne Diseases and the Investigation of Outbreaks of Food Poisoning (GUIAVETA). Major updating of the GUIAVETA addresses the investigation of food-related factors influencing an outbreak, with the aim of recognizing where food safety was compromised, and why . The updated GUIAVETA has five chapters comprising managerial and organizational elements of the establishment of an FBD surveillance system in the countries and the ten steps in the investigation of outbreaks, set out as follows: Chapter I. Elements already developed in the first edition of GUIAVETA are taken up, stressing the necessity for organization of the system since it is unlikely that a surveillance system can be developed without adequate management. The major organizational and managerial principles in surveillance activity are developed. Chapter II. The major organizational elements prior to the emergence of an outbreak are developed, i.e. organizing and training the team, as well as the areas of notification of cases and outbreaks. Chapter III. This chapter examines topics connected to an outbreak investigation, divided into investigation of the outbreak and investigation of the food and related factors, as well as analysis and interpretation of data. The first includes factors similar to those found in the first edition while some very important items have been added, for example the compilation of an epidemic curve and how to construct and interpret a curve. The content is modified regarding the study of foods, putting special emphasis on studying the food, its processing, and the determination of factors of contamination, survival and multiplication. Investigation methods employing principles of the HACCP system are also developed. In the area of analysis and interpretation of data, the criteria for interpreting findings, a necessary element in terms of the objectives of the present guidelines, are very precisely developed. Chapter IV develops criteria and makes recommendations on the control of foods, eating-places, food handlers and the spreading of risks before an outbreak. It is extremely important that the work is not restricted solely to the investigation of people and foods, but that an adequate control structure is put in place to eliminate risk factors which may have led to the outbreak in the first place, both in the location where the outbreak started and in any other place where a similar event could occur or where the specific food is processed. Chapter V develops the required sub-headings regarding the need to draw conclusions from the outbreak, carry out recommendations, compile a final report and publish it both through the communications media and through scientific and educational presentations by the investigating team. For a better understanding of the issues, Annexes are included as reference materials in developing tasks. It is an implicit part of the functioning of the FBD surveillance system that, in the event of an outbreak, interventions must be carried out to reduce the spread of the problem and prevent the occurrence of further outbreaks. Therefore, a chapter has been added to emphasize the importance of interventions regarding foods, production centers, food handlers and efforts to communicate the risks involved. It has been noticed that generally this last task is either not carried out or is poorly done. Yet it is known to be as important as the detection and investigation of an FBD outbreak. Finally, the concluding actions arising out of the FBD outbreak investigation are listed, among the most important of which are follow-up, drawing up of a final report, dissemination to various levels, publication and communication with the Regional Information System.
2. - AIMS OF THE SURVEILLANCE SYSTEM
3. - OBJECTIVES OF THE SURVEILLANCE SYSTEM An outbreak consists of the convergence of host, agent and existing environmental factors. The purpose of the investigation then is to describe as far as possible when, where and why this convergence occurred and who are the people affected. Epidemiological research includes the study of the host, the agent and the environmental factors. If this convergence of the previously mentioned factors does not occur, there will be no outbreak. Similarly, any action that tends to keep the three factors separated will prevent outbreaks. These concepts are graphically presented in Figure 1. Figure 1: Environment, Host, Agent
Transmission and Prevention.
Note: Disease transmission occurs when the three circles intercept at X
Among the objectives of surveillance therefore are to:
- Determine the population groups that are most at risk. - Identify contributing factors in the transmission of the FBD.
4. - BENEFITS AND PRODUCTS OF THE SYSTEM Development of FBD surveillance systems and the information obtained through these systems in the countries serve to: - Promote the development of policies, laws, and regulations.
- Inform the medical welfare community in order to improve diagnostic sensitivity. - Report to the clinical and laboratory diagnostic systems in order to improve the sensitivity and accuracy of diagnoses - Inform the systems themselves.
5. - ORGANIZATION OF FBD SURVEILLANCE SYSTEMS The organization of an effective FBD surveillance program requires certain conditions that are generally present in all the countries, although their relative importance may vary. They include: - Awareness of the existence of food-related problems and FBDs in rural and urban environments and in specific social groups. - Political and technical decisions - the fundamental responsibility for a FBD surveillance system is vested in each country’s health authority. Health authorities should be committed to the establishment of an FBD surveillance system as a key component of their food safety program, and part of the National Public Health Surveillance System.
5.1 Strategies
5.2 Structuring FBD surveillance calls for an ongoing, systematic, prompt and effective procedure for capturing specific information on the occurrence and distribution of diseases, as well as on the factors that cause them. This data, when processed and analyzed, allows for better, more rational use of resources and techniques. This activity should be part of the regular, day-to-day functions of the health services and its application would facilitate development of FBD prevention and control procedures. 5.3 Stages Surveillance of FBDs, as well as other diseases, includes : (a) Data search and collection An epidemiological surveillance system should recognize the collection of key data items as of utmost importance. At this stage, standardized analytical criteria (see case definition) should be defined so that the data to be collected can be uniformly interpreted by various personnel, at different times, and in different places. This stage covers two types of data:
In both situations, entries should be recorded only after epidemiological or laboratory confirmation. (b) Processing Processing starts with the ordering of data, selecting and grouping according to specific features, and continues with tabulation, consolidation and integration of the data. The consolidation is done logically and coherently. The data are summarized in tables and graphs using ratios, indexes, and standards, among other measures, to illustrate the current situation. (c) Data analysis and interpretation Analysis is a process that permits comparison of data on FBDs. Its purpose is to establish trends with respect to regional, national and international standards. It should also identify related factors and high-risk groups. Ultimately, data analysis should identify the most vulnerable points where control measures should be applied. Analysis and interpretation should be carried out at every level: local, central/national and regional.
This report should be a complete and systematic collection of information with reference at least to the causative agent, the magnitude of the outbreak, the duration, place of occurrence, the food involved, contributing factors, and the intervention measures carried out.
Dissemination refers to the publication and distribution of information to interested sectors. The principal users of the information collected are health professionals, service providers, food inspection services, consumer representative organizations in the food production chain and various kinds of community organizations. Information dissemination is the best way of hastening notification, either formally or informally. Diseases carrying highest importance and priority should be given special attention to ensure prompt divulgence of the principal elements for identification and notification. (f) Action policies Surveillance should provide continuous and cumulative information on FBDs in the population and on the contributing factors that influence their occurrence. This information becomes the basis for decision-making by those in charge of formulating policies and plans and directing food safety programs. (g) Evaluation Evaluation consists of measuring and drawing conclusions on the pattern of the FBD and the impact of the measures taken. 5.4 Operational Methods Operating an FBD surveillance system depends on the level of health services development, the available resources, local tradition and the relative importance of various FBDs in each country. The system should cover the collection of morbidity and mortality data, and the reporting, flow and analysis of data at every level of the health services. There are normally three levels of organization in countries:
At this level are the various health care and community agencies that are responsible for collecting, processing, interpreting and serving as the primary informants in the system. This level also links the most remote units of the public health surveillance system, which in conjunction with the FBD surveillance system should develop the required initial actions for which they have the technical capacity, and then send the information obtained to higher levels, for consolidation and processing. The surveillance system personnel at this level, being in closest contact with the community, should have basic training in FBD surveillance, in order to take prompt prevention and control measures, and put forward justification for programming. Staff of all medical care units, including doctor’s offices in the community, workplaces, schools, primary care polyclinics and other establishments, should be aware of the basic elements of FBD outbreak surveys, including methods of collecting information following an established framework, collecting clinical samples and foods. Patients and their relatives should be educated on the necessity of taking part in the survey, as well as on ways of storing and preserving the foods that could be responsible for the outbreak to facilitate sampling by the survey team. The Primary Health Care medical team should have the technical capacity to offer the best services. Once the survey team has been established it should begin the search for persons at risk including both those who became ill and those who did not. Quick work will ensure survey quality, since information will otherwise be lost as, among other things, people forget events, sampling becomes more difficult, and food samples may not be found. (b) County/Parish Level This is the intermediate level between the local and central levels, and is the level at which information received from the local level is condensed, analyzed, and evaluated, and administrative measures which are necessary are put forward with regional flexibility. If necessary, the county/parish staff will participate in surveying outbreaks as part of support for the local level, and supplement laboratory services where local levels lack capacity. This level should also disseminate information from the local level, summarize it with the necessary remarks on alerts or prevention, and send it to both the national level and back to the local level that it supports. (c) Central Level The central level is the highest level of coordination in the national FBD surveillance system, providing standardization and advisory services to other levels. The information received at this level is condensed, processed and analyzed to determine the status of FBDs in the country, and returned as feedback to the county/parish and local levels that generated the information. The results of the evaluation provide information to define policies relating to strategies for the control of the FBDs that represent health problems in the country. The central level also participates in surveys of major outbreaks. It prepares programs that link intersectoral involvement at all levels. It also coordinates the involvement of national laboratories and reference centers in clinical and food analysis in outbreak surveys. This level is also responsible for publishing the list of food analytical and clinical laboratories, and which analytical facilities (national and/or regional), provide reference or follow-up services to facilities that lack them, or reference services to other levels. The local level should be informed when changes occur in the flow of information and a report enters the system at the county/parish or central level. The central level is responsible for sending out bulletins on FBDs to international organizations, in accordance with the obligations of countries. 5.5 Operation The nature of Food Borne Diseases, at least those with the greatest social and economic impact, makes it necessary to decentralize action in order to control their effects. This is not to say that other levels of the system, or agencies external to it, should not be kept informed, or even if the need arises, get involved in the initial control phase and, subsequently, in the evaluation and supervision. To this end, it is useful when setting up a Food Borne Disease Information System to consider the existing, formal structure of local, county/parish (one or more), and the central levels, and the basic reporting units. These basic units are the ones that initially trigger off the system and in some cases, even take the first action against the problem. They must however, inform the appropriate official level of the facts, the action taken, and the results of such action. 5.6 Information Dissemination One of the aims of the FBD surveillance system is the compilation of information on the occurrence and distribution of FBDs with detailed information on outbreaks surveyed. These activities support identification of the areas, population groups, establishments, and hazardous foods, as well as critical points that are necessary for implementing prevention and control measures. This information should be put to use promptly, and therefore the system should provide feedback to its formal and informal sources of information. The FBD surveillance system should provide for reporting to the community at large on the status of FBDs in the country, their impact on health, and the prevention and control measures implemented. Countries should have such means of communication for putting out information on FBD surveillance as epidemiological bulletins (weekly or quarterly) with information compiled at various levels. These bulletins should feature tables and graphs showing occurrence, distribution, and the reports of surveys on FBD outbreaks. The community should be kept up to date through the press, radio and television, and through the promotional services for social and community development. This information will stimulate interest in the report, motivate people to continue cooperation, and support the diffusion of general prevention measures. The mass communication units of the coordinating institutions for FBD surveillance should be functionally integrated into the System. They will create the messages, ensure their distribution to the media, and draw up a strategy for getting technical data to the population, making sure to cover national, county and local levels. The FBD surveillance system in each country should forward information to the Regional Information System on Food Borne Disease Surveillance so that the region is made aware of the impact of FBDs. PAHO/WHO will promote and support development and strengthening of national information and surveillance systems and will disseminate pertinent information on FBDs from surveillance in the countries. 5.7 Laboratory Support Services The existence of laboratories for diagnosis of clinical and food samples, as a part of the System, is fundamental to the implementation of an FBD surveillance system. A national network of public health laboratories and a network of food analysis laboratories, or an integrated network of the two, should therefore be developed or reorganized in terms of standards, implementation of accreditation systems for laboratories, and standardization of procedures. This will make it possible to identify the level of development and the analytical capacity of the laboratories and will facilitate integrated and coordinated planning of FBD surveillance activities. Mechanisms should be established to ensure implementation, at local level, of a minimum amount of laboratory facilities for the isolation of etiologic agents of the genera Salmonella,, Shigella, Staphylococcus, Clostridium, and E. coli. Diagnostic specificity should be ensured at the national level and at Reference Laboratories, where techniques will be available for serotyping and determining the resistance of these agents, and for the development of other epidemiological tracers. Some selected laboratories should also have access to technology for detection of chemical and biological residues (pesticides, heavy metals, mycotoxins, anabolic agents, veterinary drugs, additives and other contaminants), but all laboratories should be actively involved in the standardization of techniques and procedures as well as in the development of new diagnostic methods. A network census should be published in order to identify analytical capacity, specialists and those in charge of each facility with its address. The clinical laboratory may contribute to FBD outbreak investigations through sampling clinical specimens and making a timely diagnosis to identify the causative agent in clinical samples. Apart from the isolation of pathogenic bacteria common to clinical samples, an additional classification of types/subtypes is necessary in order to show the epidemiological relationship to strains isolated from food and animals. This detailed typing is usually carried out by a reference laboratory. The role of food laboratories in FBD outbreak investigations is to advise on sampling, and to carry out diagnosis in order to identify the etiologic agents and the factors contributing to the lack of food safety. When it is appropriate to consider additional sampling, jointly with the clinical laboratory, the typing of the microorganisms should be carried out for comparison with isolated strains and should contribute to the determination of molecular epidemiological patterns and to the knowledge of the microbiological characteristics and the geographical distribution of the agents involved. Laboratories should rely on standardized procedures for the collection, description, identification, preservation, and shipment of clinical specimens (stool, vomit, blood, urine) and food samples. These standards should be developed for the FBDs that are considered priority. A very important factor to develop within laboratories is the possibility of detecting cases of FBD starting from results obtained during routine work. Laboratory workers should be trained in basic aspects of epidemiology and hygiene, while the staff of the epidemiological and hygiene services should have a basic knowledge of the capacities and functions of each laboratory participating in the system. In regions where red tide, ciguatera, and other marine toxins constitute a risk factor, integration of a monitoring network for these neurological or pathological entities with a reference laboratory should be pursued. PAHO/WHO will mobilize resources for technical cooperation in reference services and in technology transfer, standardization of analytical techniques and training of personnel in the field of FBDs.
5.8 Epidemiological Studies With the FBD surveillance system implemented and consolidated, information and hypotheses soon become available that will allow for the conducting of the broader epidemiological studies. These studies may be in the following areas:
5.9 Supervision, Training, and Education Supervision for FBD surveillance should be clearly delineated, with a workable methodology and objectives different from those of traditional supervision. The collection of samples, and other field research activities, must be performed during the investigation, as its principal function is to develop continuing in-service training for staff. Adequate, prompt and sufficient financing of FBD surveillance activities is a fundamental requirement, and is by its very nature a state responsibility. The FBD surveillance system should establish a training program:
Technical advances in this field demand constant updating. Training in food safety is therefore fundamental. Its objective is the prevention of FBDs by making people aware of changes, their rights and duties in collaboration and involvement as well as behavioral changes in food handling and consumption practices. To achieve this, the purpose and the scope of FBD surveillance must be communicated to people in order to ensure their active involvement. The best means of bringing about behavioral change in the family is through school-aged children. Training educators in food safety issues and including food safety as a subject in the daily activities of the school are therefore recommended. The activities mentioned above can be supported by the design of enabling and communication strategies:
5.10 Evaluation of the System Evaluating the system involves measuring and passing judgement on its functioning, thus making it possible to identify the problem and carry out actions towards redirecting efforts. Basically, epidemiological factors and administrative and control measures are evaluated. A. - Epidemiological Factors
B. - Administrative Factors
C. - Interventional Factors
D. - Case report level (proportion of cases detected by the system)
1. Pan American Sanitary Code. Bulletin of the Pan American Sanitary Bureau, Vol. 4, N°2, Feb. 1925. Pan American Bond. Washington DC. USA. INPPAZ - PAHO -
WHO
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