5
Public Health Surveillance System

A fundamental tool that must be included in any approach to the problem of controlling communicable diseases following mass population movements for any cause is a public health surveillance system. A well-designed surveillance system allows for rapid identification of increases in cases of communicable diseases in an affected area, signaling the need for a specific response. Basic demographic data should be collected, in addition to simple case counts using standardized case definitions. These include age, sex, pregnancy status, location of residence in the settlement area, and so forth. These data can be used to identify high-risk subgroups in the general population or areas in a settlement that might require specific attention (e.g., previously unrecognized vector breeding sites).

Another aspect of surveillance that is often overlooked is ongoing monitoring of first-line antimalarial drug efficacy among the affected population. Drug efficacy can change dramatically over relatively short periods of time, especially in areas where antimalarial drugs are easily obtainable in the community. Periodic monitoring (at least once every two years and in some situations as often as once a year) of the drugs used for first-line treatment of malaria should be a priority. Monitoring in-hospital case fatality rates can aid in the early recognition of declining efficacy of second-or third-line antimalarial drugs as well as identify other operational problems with the management of malaria patients.



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Malaria Control During Mass Population Movements and Natural Disasters 5 Public Health Surveillance System A fundamental tool that must be included in any approach to the problem of controlling communicable diseases following mass population movements for any cause is a public health surveillance system. A well-designed surveillance system allows for rapid identification of increases in cases of communicable diseases in an affected area, signaling the need for a specific response. Basic demographic data should be collected, in addition to simple case counts using standardized case definitions. These include age, sex, pregnancy status, location of residence in the settlement area, and so forth. These data can be used to identify high-risk subgroups in the general population or areas in a settlement that might require specific attention (e.g., previously unrecognized vector breeding sites). Another aspect of surveillance that is often overlooked is ongoing monitoring of first-line antimalarial drug efficacy among the affected population. Drug efficacy can change dramatically over relatively short periods of time, especially in areas where antimalarial drugs are easily obtainable in the community. Periodic monitoring (at least once every two years and in some situations as often as once a year) of the drugs used for first-line treatment of malaria should be a priority. Monitoring in-hospital case fatality rates can aid in the early recognition of declining efficacy of second-or third-line antimalarial drugs as well as identify other operational problems with the management of malaria patients.

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Malaria Control During Mass Population Movements and Natural Disasters PRACTICAL CONSIDERATIONS FOR SURVEILLANCE SYSTEMS The success of a surveillance system rests on the availability of a functional communication and logistical infrastructure that allows for timely information transfer among all users of the system. For surveillance systems to be effective, the flow of information must occur in two directions—the data must be fed into the surveillance system and a practical interpretation of the data must be returned to the health care workers. Health care workers need to receive timely feedback on the statistics they are collecting in order to make policy or programmatic decisions, particularly if there is suspicion of a pending epidemic. Additionally, if information mostly flows into the system and little or no information is returned, enthusiasm for collecting and reporting quality data will wane, jeopardizing the validity and usefulness of the system. The Centers for Disease Control and Prevention (2001) published a useful guide to evaluating surveillance systems. Many health care workers in refugee camps have minimal training and do not understand the importance of malaria surveillance; therefore, it is wise to spend time training workers not only in how to systematically collect data but also about the potential impact these data can make in case management. For example, in the Thai/Myanmar border camps, a medic who received such training was able to rapidly detect an epidemic. Because the supervising nongovernmental organization physician was only able to visit the camp intermittently, not having well-trained and motivated camp staff might have led to a much larger outbreak (MacArthur et al., 2001). STANDARDIZED CASE DEFINITIONS1 A primary problem facing malaria surveillance is the choice of a single case definition and obtaining agreement on standardized reporting of data, especially in situations where multiple NGOs are providing health care services. Without standardized case definitions and reporting systems, the ability to produce reliable interpretation of surveillance data to determine disease trends in an affected population is questionable. Wherever possible, malaria cases should be confirmed using an accepted laboratory test (such as examination of blood slides). Commercially made rapid diagnostic tests for malaria are available and could be 1   See also Diagnosis of Malaria in Chapter 6.

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Malaria Control During Mass Population Movements and Natural Disasters used but currently are cost prohibitive in many settings. Besides improving the specificity of reporting, the use of microscopy will identify patients with nonmalarial febrile disease requiring further investigation, identify patients with nonfalciparum malaria, identify patients with hyperparasitemia, and reduce the amount of inappropriate antimalarial drug use. In circumstances where routine microscopic diagnosis is not possible, such as situations where health care facilities are unable to perform microscopy or lack the capacity to keep up with the patient load (a frequent situation in the acute phase of an emergency), a simple clinical case definition can be used. A commonly used definition is “fever or history of fever in the absence of an obvious cause.” The use of clinical case definitions, however, will overestimate the incidence of malaria. Surveillance systems that rely on clinical case definitions should be complemented with periodic blood slide surveys of patients meeting this definition to aid in the interpretation of surveillance data. Public Health Surveillance System: Key Points Effective surveillance is essential for monitoring disease trends and providing early warnings of potential epidemics or increasing drug resistance. Ongoing monitoring of first-line antimalarial drug efficacy should be a routine form of surveillance for the affected population (see special studies). A functional communication system and logistical infrastructure is necessary for timely information transfer between participating facilities or organizations. To be useful as feedback for clinical management decisions, surveillance information should be summarized and returned to clinical services in an efficient manner.

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Malaria Control During Mass Population Movements and Natural Disasters RECOMMENDATIONS Our main recommendations for policy makers and field staff are: Ensure that a functional surveillance system for communicable diseases is operational as early in an emergency situation as possible. Provide necessary training in the use of surveillance information for all health care and administrative workers involved with surveillance. Require standardization in case definitions and forms used by all agencies. Establish a system for ongoing drug efficacy monitoring of first-line antimalarial therapy. Provide timely feedback to health care agencies summarizing the implications of the surveillance data.