WHO surveillance case definitions for ILI and SARI

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NLiS Country Profile: Afghanistan
Delta hepatitis and infection in North America. When breast milk alone no longer meets the nutritional needs of the infant, complementary foods should be added. In , Eugen Baumann observed iodine in thyroid glands. The benefit of constructing such a framework, over and above the complete review of the chain of events which determine the nutritional situation, is to allow the expression, in measurable terms, of general concepts which, because of their complexity, are not always well defined. Global Nutrition Monitoring Framework. Examiner reliability was considered acceptable in both surveys 4,

Nutrition Landscape Information System (NLiS)

Disease surveillance

In theory this depends on their ability to best reflect a sometimes complex reality, but a trade-off will have to be found given the level of difficulty in collecting them.

Therefore, indicators are traditionally defined according to a certain number of properties that allow their value to be assessed, at least in a given context.

Obviously they do not all present all the characteristics of a good indicator, so that it will have to be decided which characteristics are to be given priority when selecting indicators. It entails that the indicator does indeed offer a true and as direct as possible measurement of the phenomenon considered. At conceptual level, it depends first of all on how clearly the phenomenon to be measured has been defined and also on the ability to measure it directly.

This poses a problem where the phenomenon to be measured is linked to a multidimensional concept, and is thus difficult to measure in a global way. There must, in particular, be a consensus on the level and significance of cut-off points for classification. A major standardization effort has for example been made in the field of measuring nutritional status and recommended dietary intakes, and this has helped give a more precise framework for use of the corresponding indicators.

This is not always the case in other sectors, either because the indicators lend themselves less to quantification, or because such quantification depends very much on local circumstances. Relevance in the context of planned use must, in this case, be based on a local analysis shared among the different stakeholders, as we will see below.

Moreover, even if the indicator correctly describes a phenomenon, any systematic bias in collecting the corresponding information due to measurement methods or instruments will affect its validity. There is no overall indicator to provide a picture of "nutritional status", therefore a decision has to be made on which specific aspect of nutritional status is to be characterized: Even in the case of energy status, for example, no overall indicator is available; the indicator which is the most relevant for the aspect one wishes to prioritise - physical, biochemical, functional, etc.

For assessing the nutritional situation of a population, a set of individual anthropometric measurements have been adopted, that, when compared to reference values, make it possible to assess the status of individuals or populations; they constitute the corpus of relevant indicators to be used preferably over any other. However, when using these indicators, one should be aware of limitations to their validity: In the field of "food security", - again a very broad concept difficult to translate in simple terms - there is a considerable number of indicators, each reflecting a specific aspect and thus only relevant for a given aspect.

For example, in order to describe the level of food insecurity of a household, an indicator based on a quantitative criterion of food consumption or a qualitative criterion of the perception by the household of its own food insecurity situation will be more relevant than an indicator of prices of foodstuffs on the local market. Imprecision due to measurement methods, variability from one day to another may limit the reproducibility of the indicator.

This causes an increase in variance and implies that larger samples will be needed in order to assess correctly the level of the indicator and its variations over time.

Subjectivity bias is a frequent risk with indicators deriving from qualitative surveys, as they describe behaviours or opinions of households, for example, since the personality or technique of the person conducting the survey may influence the nature of responses. Moreover, respondents to a questionnaire or subjects under observation can modify their responses or behaviour in a normative way.

People who are overweight, for example, often minimise their actual food intake when interviewed for a food consumption survey. Reproducibility guarantees that an indicator can be measured at repeated intervals in a comparable manner - a quality which is crucial when using the indicator to assess and monitor the situation.

A complementary characteristic is specificity, which refers to the ability to identify those not affected by the risk or characteristic. Sensitivity is measured in practice by the ratio of the number of individuals identified by the indicator as being at risk or as having the characteristic to the number of individuals who are actually at risk or have the characteristic. Specificity is the ratio of the number of individuals not identified by the indicator to the number of individuals who are actually not at risk or do not possess the characteristic.

Sensitivity thus gives an idea of the degree of correct or misclassification linked to the use of an indicator. Not all indicators lend themselves to an assessment of sensitivity. Sensitivity applies essentially to indicators with cut-off values. Moreover, sensitivity is measured with respect to a given goal; sensitivity of an indicator such as weight-for-height at a given cut-off value will not be the same, depending on whether the goal is to identify children who are wasted or those who are at risk of dying in coming months.

Data for quick computation of these parameters sensitivity, specificity are not always available, so in practice, reference is made to existing data from the literature to find those closest to the chosen cut-off values and expected prevalences. One particular aspect of sensitivity is the ability of an indicator to measure change, not in order to identify or target a particular category of individuals as previously but to detect the smallest possible change in the phenomenon described, in a significant way.

While sensitivity, in general, is important when establishing a baseline, and for defining the target groups to which the activities will be directed, this ability for measuring change is crucial for assessing or monitoring trends, in particular to detect changes in the situation during implementation of the programme. However, it is relatively inert when assessing small progressive changes in nutritional status over time, and the weight-for-height indicator will be preferred in this case, since it is more sensitive to change.

Also, urinary iodine will respond to introduction of salt iodization in a region quicker than prevalence of goitre, which will decline only slowly. In addition to these inherent characteristics of indicators, their operational value should be examined; it will be essential when the choice of indicators is made, especially in terms of speed and cost of collecting data for producing these indicators.

It represents the practical possibility of making available the indicator in question. It implies the feasibility of collecting the corresponding data by whatever means. There are indicators described as "ideal" which nobody is in practice able to collect. As a result of major international conferences and of programmes that have followed them during the last two decades, many of the required indicators are already systematically and regularly collected within the framework of such programmes and are thus very easily available.

It affects use of the indicator not only at the descriptive stage, but also when monitoring the situation. An indication of the quality of the measurements, of sampling and of the confidence interval of the result is essential here to assess dependability.

Occasionally, it has been observed that the number of malnourished children estimated by nutritional surveys carried out by various organizations on identical populations and during the same periods, differed substantially; using the results for targeting purposes or for monitoring the situation is ruled out in this case.

The reason was usually the lack of precision of the anthropometric measurements or of the definition of age, and occasionally a sampling problem. Data on food consumption obtained by weighing food are more precise than those obtained with the "recall" technique, although the former implies technical constraints and can therefore only apply to small samples, so that there is a broad confidence interval in the results.

Recall techniques, on the contrary, can easily be applied to a large sample, obviously with a smaller confidence interval. The various available data must therefore be carefully examined before using them for monitoring purposes, and a choice will sometimes be made between data collected with a higher level of accuracy but lower power at the level of the target population, or the opposite.

On this depends, in part, the speed and frequency with which the indicator can be regularly measured. When the data necessary for the construction of the indicator need to be collected specifically for evaluation or monitoring, cost should be considered; it depends on the difficulty and sophistication of the measurements, the accessibility of the objects or people to be measured, the frequency of collection and the complexity of the analysis subsequently.

The cost of non-collection may be measured, in the case of a food subsidy programme, for example, by the difference between the cost of the programme if it is carried out without particular targeting, in the absence of any indicator allowing targeting, and the cost of the programme for the target population, plus the cost of targeting, if the programme is to be directed at a high risk group only.

Nevertheless, information on the cost of collecting an indicator for each situation is seldom available. It is difficult to measure, and estimates are generally based on the cost of different types of survey within the country, taking account of the fact that several indicators are collected at the same time. Indicators can be categorized schematically in the following way according to the level at which they are produced or made available:. They include both indicators regarding the implementation of services as well as indicators regarding the situation or the impact of actions under way.

It is generally easy to obtain them from the departments concerned, which usually have time series that are very useful in distinguishing medium- and long-term trends. Even so, it is not always possible to cross-tabulate these indicators, since they do not necessarily come from the same databases and are accessible only in a relatively aggregated form. It is also difficult to verify the quality of the original data.

Lastly, even if the data are collected on a frequent basis monthly reports, for example , recovery and analysis may take too long. Such data tend not to be immediately accessible except in summary form, although it is easy to organize new analyses with the departments in charge of them.

These data allow statistical cross-tabulation to be made between the many variables collected simultaneously on the sample. Although carried out at best at very long intervals, they can be updated with reasonable projections, especially if information on trends in the fields of interest, based on routinely collected data, are also available. These data are often kept together in national statistical offices.

They consist of a regular collection of information based on a small number of selected indicators. The system varies by country, those that perform best are based on an explicit conceptual framework and are linked to a clear decision-making mechanism. They can represent a sound basis for central monitoring. A particular category is derived from surveys conducted by international bodies for various purposes: These cross-sectional surveys are conducted directly at household level on samples which are representative at national level but of variable size; they include a wide variety of indicators in number, goals and qualities and are now frequently repeated.

Although conducted peripherally, they are generally available and used centrally. These sources, which are in principle fairly reliable, benefit from an advanced level of analysis allowing causal inference to be derived of relationships among various household indicators, and with individual indicators, such as nutritional status. They represent a precious source when establishing a baseline and when analysing causes prior to launching an intervention. These are constructed primarily on the basis of routinely collected data from local government offices, community-based authorities.

They are usually passed on as indicators or raw data to the central level, and then sent back to the decentralized levels, with varying degree of regularity, after analysis.

They are often disaggregated by district or locality, but are not always representative, since they often refer only to users of the services under consideration.

They are generally grouped together at the central administrations of regions or administrative centres. The indicators relate primarily to activities that lend themselves to regular observation, either because they record activities indicators of operation or delivery of services or because they are necessary for decision-making crop forecasts, unemployment rates or for monitoring purposes market prices of staples, number of cases of diseases, etc.

They do not necessarily include indicators of the causes of the phenomena recorded and are not in principle qualitative indicators. Indicators collected at decentralized levels should meet both the needs of users on these levels and also those of users on the central level for the implementation and monitoring of programmes. If these regularly compiled indicators do not have any real use at the local level and are intended only for the national central level, there is a danger that their quality will drop over time, for lack of sufficient motivation of those responsible for collection and transmission - and gaps are therefore often found in available data sets.

Nevertheless, they are invaluable in giving a clear picture of the situation on the regional or district level, together with medium-term trends. Generally speaking, their limitation is the low level of integration of data from different sectors. A certain number of indicators, particularly those concerning the life of communities or households and not touching on the activities of the various government departments, are not routinely collected by such departments and are in any case not handed on to the regional or central offices.

They are sometimes collected at irregular intervals by local authorities, but most often by non-governmental organizations for specific purposes connected with their spheres of activity - health, hygiene, welfare, agricultural extension, etc. Analytical capabilities are often lacking at this level, and the available raw data may not have led to the production of useful indicators.

Action therefore should be taken to enhance analytical capacities or else sample surveys will have to be carried out periodically on these data in order to produce indicators. A sound knowledge of local records and their quality is needed to avoid wasting time. New collection procedures often have to be introduced for use by local units, while being careful not to overload them or divert them from their own work.

Otherwise a specific collection has to be carried out by surveying village communities targeted for analysis or intervention.

These surveys are vital for a knowledge of the situation and behaviours of individuals and households and an evaluation of their relationship with the policies introduced. In general, they offer an integrated view of the issues concerned. They may have the aim of supplying elements concerning the local situation and local analysis, in order to confirm the consensus of the population and of those in charge as to the situation and interventions to be carried out, and also to allow an evaluation of the impact of such interventions.

The participatory aspect should be emphasized rather than the precision or sophistication of data. An FAO work on participatory projects illustrates issues of evaluation, and especially the choice of indicators in the context of such projects FAO If data already collected are used or if a new survey is carried out for use on a higher level, the size and representativeness of the sample must be checked, and it must be ensured that the data can be linked to a more general set on the basis of common indicators collected under the same conditions method, period, etc.

Verification of the quality of the data is crucial. Before undertaking a specific data collection, a list of indicators and of corresponding raw data should be developed which can be used by services at all levels; it is not unusual to find that surveys could have been avoided by a better knowledge of the data available from different sources. To track down these useful sources and judge the quality of the data available and their level of aggregation, a good understanding is needed of the goals and procedures of the underlying information system.

The country had set up a monthly national information system on production estimates for 35 crops, covering information on crop intentions, areas actually planted, crop yields and quantities harvested in each state. The information was obtained during monthly meetings of experts at various levels - local, regional and national.

The information was then put together at the state level, and then at the national level, reviewed by a national committee of experts, and sent on to the central statistics office. The different levels thus had some rich information at their disposal, coming from a range of local-level sources.

Although it was certainly fairly reliable, being confirmed by a large number of stakeholders and experts, its precision could not be defined, in view of its diversity. The usefulness of such data varies depending on information needs and thus on the quality of the data required. Data concentrated at the central level are probably useful primarily for analysing trends. On the other hand, apart from the figures, more general information on production systems exists at local level, and this can be useful for identifying relevant indicators of causes, or for simplifying monitoring of the situation.

We have seen that there is a great number of indicators which differ widely in quality; the availability of corresponding data is variable, and any active collection will be subject to constraints.

Therefore the choice of indicators must be restricted to the real needs of decision makers or programme planners. This implies that a method is needed for guiding the choice. The main elements that will guide choice are: Any intervention is based on an analysis of the situation, an understanding of the factors that determine this situation, and the formulation of hypotheses regarding programmes able to improve the situation.

A general framework was presented earlier see Figure , representing a holistic model of causes of malnutrition and mortality, which was endorsed by most international organizations and nutrition planners. However, the convenient classification that it implies, for instance into levels of immediate, underlying or basic causes needs to be operationalized through further elaboration in context.

The benefit of constructing such a framework, over and above the complete review of the chain of events which determine the nutritional situation, is to allow the expression, in measurable terms, of general concepts which, because of their complexity, are not always well defined.

For example, it is not enough to refer to "food security"; one should state which of the existing definitions is to be used, on which dimensions of food security the focus is placed and the corresponding indicators. The use of conceptual frameworks when implementing programmes or planning food and nutrition is not new. Many examples have been developed, focusing on different aspects.

The concept of food security is generally perceived as that of sufficient availability of food for all. However, several dozen different definitions have been proposed over these last 15 years! This concept may, for example, comprise different aspects depending on the level being related to: In the first case, analysis will focus on agricultural production, and in the second the emphasis will be on improving the resources of those who lack access to a correct diet.

This preliminary brainstorming exercise will allow a better definition of the perceived chain of causes production shortfall, excessive market prices, defective marketing infrastructures, low minimum wage, low level of education, etc. Further, there is considerable public pressure to make this information available quickly and accurately. Formal reporting of notifiable infectious diseases is a requirement placed upon health care providers by many regional and national governments, and upon national governments by the World Health Organization to monitor spread as a result of the transmission of infectious agents.

Since , WHO has required that all cases of the following diseases be reported to the organization: In , the list was extended to include polio and SARS.

Regional and national governments typically monitor a larger set of around 80 in the U. Tuberculosis , HIV , botulism , hantavirus , anthrax , and rabies are examples of such diseases. The incidence counts of diseases are often used as health indicators to describe the overall health of a population.

The World Health Organization is the lead agency for coordinating global response to major diseases. The WHO maintains Web sites for a number of diseases, and has active teams in many countries where these diseases occur.

WHO 's Epidemic and Pandemic Alert and Response EPR to detect, verify rapidly and respond appropriately to epidemic-prone and emerging disease threats covers the following diseases: As the lead organization in global public health, the WHO occupies a delicate role in global politics. It must maintain good relationships with each of the many countries in which it is active. As a result, it may only report results within a particular country with the agreement of the country's government.

Because some governments regard the release of any information on disease outbreaks as a state secret, this can place the WHO in a difficult position. The WHO coordinated International Outbreak Alert and Response is designed to ensure "outbreaks of potential international importance are rapidly verified and information is quickly shared within the Network" but not necessarily by the public; integrate and coordinate "activities to support national efforts" rather than challenge national authority within that nation in order to "respect the independence and objectivity of all partners".

The commitment that "All Network responses will proceed with full respect for ethical standards, human rights, national and local laws, cultural sensitivities and tradition" ensures each nation that its security, financial, and other interests will be given full weight. Zoonotic surveillance system diseases found in animals that can be transmitted to humans involves a system for detecting infected animals. Mosquitoes and blood were collected and tested for WNV in 10 counties.

In addition, veterinarians were asked to test horses with neurologic symptoms consistent with WNV. Health care providers were reminded of reporting and diagnostic criteria for possible human cases of WNV Blackmore As a result, detection of WNV led to public health control measures, such as advising the public to protect against mosquito bites and intensifying mosquito abatement efforts.

The purpose of this system is to gather information about negative effects experienced by people who have received approved drugs and other therapeutic agents. Reports came from health care providers, including physicians, pharmacists, and nurses, as well as members of the general public, such as patients or lawyers, and manufacturers. Because AERS and VAERS are passive surveillance systems, they may be limited by underreporting or biased reporting, and they cannot be used to determine whether a drug or vaccine caused a specific adverse health event.

Instead, these systems are used as early warning signals. This surveillance system is a relatively new surveillance method that uses clinical information about disease signs and symptoms before a diagnosis is made. It is an active or passive system that uses case definitions that are based entirely on clinical features without any clinical or laboratory diagnosis for example collecting cases of diarrhea, rather than cases of cholera.

This syndromic surveillance system uses electronic data from hospital emergency rooms, and provides the health department with early notification of the outbreak.

Registries are a type of surveillance system used for particular conditions, such as cancer and birth defects. They are often established at a state level to collect information about persons diagnosed with the conditions.

This information can be used to improve prevention programs. Public health laboratory data is another source of surveillance data which routinely conduct tests for viruses, bacteria, and other pathogens. Laboratory serotyping provides information about cases that are likely to be linked to a common source.

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