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BIREME - PAHO - WHO

GuiaVETA
Guidelines of Surveillance System for Foodborne Diseases and Investigation of Outbreaks

CHAPTER II.

ORGANIZATION OF THE FOOD-BORNE DISEASE SURVEILLANCE SYSTEM

1. Reporting

Reporting is an activity through which the FBD surveillance system obtains regular, continuous and timely information on the occurrence of cases of FBD and, especially, on the existence of outbreaks. In response to the occurrence of outbreaks, epidemiological research is carried out, using active case findings and the acquisition of data through direct surveys.

This guide adopts Bryan’s proposal, but with modifications ², as presented in Table 1.

Numerous FBDs present similar clinical profiles that sometimes make diagnosis and reporting difficult, thus making it necessary to periodically review the criteria contained in Annex F of this guide.

Table 1. Classification of the FBDs according to Bryan (modified)

In reporting FBDs, it is suggested that the health services use coding based on the International Classification of Diseases (ICD) ³, which appears in "Annex a."

For correct identification and subsequent reporting, local health service personnel should have at least a general knowledge of the symptoms and clinical profiles of the most frequent FBDs in each country or region. For this reason, a list of FBDs classified according to symptoms, incubation period and types of agent is presented in "Annex E"; furthermore, the food frequently implicated, samples that should be sent to the laboratory and factors that contribute to outbreaks of FBD are specified for each of them.

2. - Sources of Reporting

There are both formal and informal sources of FBD reporting.

The formal reports of FBDs should be directed to the health authorities and be carried by both public and private health sectors and for the social services system, by those in charge of restricted communities (such groups as day-care centers, schools, prisons, barracks, geriatric homes and others), and by public and private laboratories. All these sources should report the FBD using a chosen means (forms, official reports, e-mail, fax, telegram, telephone, mail, etc.).

A useful methodology in FBD surveillance is to select "sentinel posts" in specific risk areas. The selection criteria are: places that present risks of epidemic outbreaks of FBD (schools, day-care centers, public dining rooms, industrial and other kitchens) or local health services that have a marked record of FBD (emergency services, outpatient reception areas of some hospitals, toxicology services, etc.).

Informal reports are generated occasionally and spontaneously, by sources not involved in the field and under no obligation to report. The reports can be:

This report can arise from patients, their relatives or friends, people from the communities and institutions that have implemented simple methods of surveillance for symptoms and signs of FBD.

There are many methods of detecting and reporting the diseases on a local and provincial basis, and these can be incorporated in the FBD Surveillance Program. Among the most common are:

• Compulsory or voluntary reporting of specific infectious diseases according to the epidemiological system of each country.

• Passive recording of responses to daily enquiries in physician’s offices, polyclinics, and hospitals.

• Reports from the people to health agencies.

• Reports from workplaces, schools, and other ‘closed’ centers.

• Reports on absence of students and workers from their studies or workplaces.

• Reports from ‘sentinel posts’ established for certain diseases among auxiliary centers, schoolchildren or populations.

It is a fundamental principal that all reports be coordinated with the FBD surveillance system and that the system be in a position to respond rapidly and effectively. People who report should be assured that the information is noted and investigated and that intervention measures are taken. For this reason, the general population (housewives, schoolchildren, teachers, community leaders, etc.) should know the principal clinical, epidemiological characteristics of Food Borne Diseases, why and how they occur, the importance of reporting cases( even suspects), as well as preventive measures to be taken.

Another methodology for the surveillance of FBDs consists of considering the services that are characteristic of the Food Safety Programs, clinical and food-analytical laboratories, toxicology information centers and other similar specialized sources of permanent reporting of FBD. Surveillance is thus directed toward isolation and identification of causative agents and the determination of certain epidemiological guides to the agents, which make it possible to obtain essential information, not available through exclusively clinical methods.

To improve reporting on cases and outbreaks of FBD, the following activities are recommended:

• Review existing information mechanisms in the disease surveillance system that can be incorporated into the FBDs surveillance system. Among these, the system alert-action, the daily information system, and statistical and other reports can be highlighted.

• Identify the types of information that cannot be obtained from the established systems but that need to be collected. Use the data collected from the FBD surveillance system to establish ways and means of extracting the information needed by the systems.

• Identify, motivate and involve institutions, branches and personnel who are willing to assist.

• Train all personnel that are enlisted in the system in order to achieve an appropriate response.

• Install telephone lines so people can call in reports and, to this end, publish the numbers in the telephone directories and all other usual places.

• Establish record books in the appropriate health units.

• Stimulate involvement in the program through risk dissemination and communication activities.

• Promote tourism information by means of a specific system.

Every unit dedicated to prevention and epidemiology should have properly defined mechanisms for receiving complaints and information on sanitation in establishments regarding the sale of unsafe food, people who have fallen sick or on cases and outbreaks of FBD. A record book should be available for complaints and information from individuals, with reports numbered consecutively. Rapid response measures should be developed as the circumstances require and allow, and the results should be communicated to the person making the report.

FIGURE 2. FLOW CHART OF INFORMATION ON A FOOD-BORNE DISEASE SURVEILLANCE SYSTEM

In the event of information on outbreaks of FBD the highest priority should be given to investigation, control and other appropriate activities.

Persons coming forward with information should always be asked to provide names of other people who attended the event, and who will therefore be suspect whether or not they become ill, and the names of any other persons known to display the same symptoms.

Persons who receive complaints should be trained not only to respond attentively but also to give suitable instructions.

3. Case Reporting

Reports of cases of FBD are made separately from reports of outbreaks. The case report is important because it permits a greater approximation to the real incidence and becomes a potential primary source for the detection of outbreaks. Some FBDs (e.g. Campylobacter infection, hepatitis A, shigellosis) may occur most frequently as cases and not recognized as outbreaks, so that these diseases should be properly surveyed according to the possibilities and concerns.

In every case compatible with, or even suspected to be an FBD, a brief, simple report should be prepared. It is therefore important to outline a case definition of FBD.

Once diagnosis has established or confirmed the reported cases of FBD, health workers should compare them with previous records in order to identify any similarity or common indicator (consumption of a single food, or a known eating place), with other cases and attempt to determine the existence of an outbreak. Health workers should then attempt an initial characterization of the possible outbreak according to variables of time, place and person. If the outbreak is confirmed, the next step is to investigate it.

4. - Outbreak Report

The outbreak report can be prepared from formal and informal sources. Suspicion of an outbreak of FBD (two or more cases) is sufficient reason to start an investigation. This suspicion may arise from:

• Information from persons in the community on the presence of two or more sick people.

• A report from health workers that two or more cases of FBD have been observed, presumably related and fitting the definition of an outbreak.

• Reports of cases of FBD, which after careful review, may show an apparent similarity in common characteristics such as sex, age, occupation, address, date the symptoms appeared, food eaten or place of consumption.

For the report, all the outbreaks should have a diagnosis of the disease and/or syndrome by clinical-epidemiological evidence and laboratory confirmation of the agent. In any case, if the agent is not identified, the most probable clinical diagnosis of the disease should be reported.

The outbreak report should be circulated amongst the different levels of officials, following the flow chart in Figure 2, the same path followed for reportable diseases.

5. Reporting Requirements and Flow of the Information

The occurrence of outbreaks and cases of FBD should be reported immediately to the local health authorities so that they can proceed to take appropriate intervention measures. The local level will then report to the intermediate and central levels as often as is necessary.

A final report on the outbreak is completed once the conclusions in the FBD Surveillance Form 9 are obtained.

6. - Formation of a research team

Research on FBD requires the assembly of a technical team comprising at least one professional (clinical physician, epidemiologist or public health professional, veterinarian) supported by a food hygienist, and Public Health Inspectors or nursing personnel. Ideally, there should also be a microbiologist, a chemist, a communication specialist and any other person(s) considered necessary. It is also desirable, where an outbreak may justify it, for the team to include specialists from other institutions such as Ministries of Agriculture, Fishery, and Industry, and from universities and other institutions, with a view to expanding the technical, operational and scientific capacity of the working team.

Membership of the teams should be specified, with information and coordination activities distributed among the participants throughout all phases of the outbreak study.

A trained professional with a background in epidemiology and knowledge of food safety should be designated to lead the team. The leader will ensure that bulletins on the outbreak are prepared and issued, outlining the initial intervention activities and preparing preliminary and final reports.

The research team should have the necessary material and financial resources to study the outbreak including transportation (vehicles and fuel), equipment (materials for managing samples, and for processing information), stationery including forms, and facilities for shipment of samples and materials, among others.

Every local health care unit linked to the FBD surveillance system should have a directory of the investigation team, other institutions, and their telephone numbers.

The primary health care level will have available models of epidemiological surveys and materials for sampling so that, immediately the first cases are detected, personnel can collect preliminary data and proceed to take samples until the research team arrives to complete the survey. Primary level personnel should be trained to carry out this work.

7. - Training the team.

A system of continuous training should be established to train the team in recognizing:

• The real magnitude and importance of the problem of FBDs.

• The objectives of the surveillance system.

• Individual roles in the outbreak survey and the corresponding procedures to be developed.

• Appropriate interpretation of survey results.

8. - Duties of investigating personnel

Every investigation should be carried out with the highest ethical standards of professionalism among investigating personnel, who should therefore, above all else, explain to the stakeholders the purpose of the visit, conduct themselves courteously and inspire confidence in the respondents. Investigators should avoid displaying attitudes that can lead to rejection by respondents.

2. Bryan, F. L. Diseases Transmitted by Foods (A Classification and Summary) CDC. DHEM Publication No. (CDC) 75-8237. 5th Edition. 1975

3. World Health Organization. 1992 International Statistical Classification of Diseases and Health-related Problems. 10^th Review. Scientific Publication N°. 554. Three volumes. 1995