Which national surveillance system is used as the reference data source for other systems?

Reporting time schedule

Surveillance data is reported weekly on Flu News Europe, a collaboration between ECDC and the WHO Regional Office for Europe. The report is based on the data collected by sentinel physicians and reported by the nominated national operational contact points for influenza surveillance to The European Surveillance System (TESSy) at ECDC. Influenza activity is monitored throughout the year in Europe but more intensely from early October (week 40) in one year to the end of May (week 20) the following year.

Laboratory surveillance of influenza

Surveillance of influenza virus infection on a Europe-wide level requires close collaboration between virologists, epidemiologists and sentinel GP networks to generate the data necessary to inform a timely public health response.

Physicians in sentinel networks may take nose and/or throat swabs from a subset of patients with influenza-like illness (ILI) or acute respiratory infection (ARI). Some sentinel surveillance systems also collect blood samples. The specimens are then sent to the national reference laboratory and are tested for influenza viruses. For positive samples, influenza subtypes are determined. These results are used to validate the clinical reports of ILI and ARI.

The national reference laboratories also report influenza test results from non-sentinel surveillance to EISN. Specimens (nose swabs, throat swabs and blood samples) for non-sentinel surveillance can come from a wide range of sources: hospitals, non-sentinel physicians, homes for the elderly, clinics, etc.

A subset of the detected viruses is antigenically and genetically characterised. In addition, the relatedness between the circulating and vaccine strains is evaluated.

Analysis of resistance against neuraminidase inhibitors and adamantanes is also performed by measuring 50% inhibitory concentration (IC50) values, and/or by genotyping of viruses for detection of known drug resistance mutations. In Europe antiviral resistance is monitored by ECDC and WHO based on reports sent by influenza reference laboratories to The European Surveillance System (TESSy).

Data from laboratory surveillance are included in the weekly surveillance updates published on Flu News Europe.

Hospital-based surveillance

Some countries conduct surveillance for hospitalised cases presenting with severe acute respiratory infection (SARI). Depending on the country, all or a subset of SARI patients are tested for influenza virus infection.

A subset of countries reports laboratory-confirmed influenza-positive hospitalized cases every week. Depending on the country, these cases are from intensive care units (ICU) and/or other wards.

Case definitions, populations under surveillance, and data formats differ among the countries.

Data from hospital-based surveillance are included in Flu News Europe.

Mortality surveillance

Surveillance of all-cause mortality in at least 15 European countries is carried out by the EuroMOMO network. EuroMOMO also has a project called FluMOMO that estimates mortality that could be ascribed to influenza.

What is surveillance?

Health surveillance is the ongoing systematic collection, analysis and interpretation of health data essential for planning, implementing, and evaluating public health activities, closely integrated with timely dissemination of the data to enable effective and efficient action to be taken to prevent and control disease. (This draws on the CDC and WHO definitions.)

Surveillance ranges from compulsory notifiable diseases, specific disease registries (population based, or hospital based), continuous or repeated surveys of representative samples of the population, to aggregate data for recording trends on consumption patterns and economic activity.

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How are health surveillance data used?

Surveillance may be used to:

• recognize cases or clusters of cases, to trigger interventions to prevent transmission or reduce morbidity and mortality (includes the special case in which surveillance at the national level is required to recognize multi-state clusters);
• identify new health problems and emerging diseases;
• assess public health impact of health events or determine and measure trends;
• measure causal factors in disease (e.g., risk factors) to initiate actions to prevent the onset of disease;
• demonstrate the need for intervention programs and resources, and allocate resources during health planning;
• monitor effectiveness and evaluate the impact of prevention and control measures, intervention strategies, and health policy changes;
• identify high-risk population groups or geographic areas to target interventions and guide analytic studies;
• provide data for research, and develop hypotheses that lead to analytic studies about risk factors for disease causation, propagation or progression;
• measure progress toward Millennium Development Goals, or other project or program goals, including PRSP (Poverty Reduction Strategy Paper) targets.

At the local level, surveillance triggers basic public health investigations of disease outbreaks and specific control activities predominately for infectious diseases and environmental hazards. The main national level activities are: measuring trends in risk factors and disease, monitoring the effectiveness of specific interventions, conducting more complicated analysis to determine risk factors and providing technical assistance. At intermediate levels (state, province etc.) public health agencies typically share both perspectives.

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Why invest in surveillance?

Relatively small investments can be very effective in reducing death, disease, and disability. Surveillance can make the health system more effective and efficient, and better able to control devastating epidemics. It can lead to early detection of local epidemics when control is more effective, less costly, and involves less loss of life. In addition to their health impact, epidemics can have a costly impact on productivity and other aspects of the economy: the 1991 cholera epidemic in Peru involved a total loss of $770 million (primarily in the tourism and seafood industries), and the plague epidemic in India is estimated to have cost the country $1.7 billion.

Borders are ineffective in containing diseases (the 1991 cholera epidemic eventually spread throughout Latin America), so surveillance and timely dissemination of information are wise investments for countries in which an epidemic is or might be occurring, as well as countries to which it might spread.

Surveillance is also important for controlling and preventing endemic diseases that reduce productivity and can be costly to manage. Good surveillance systems permit early identification of diseases such as TB and syphilis that can be cured easily with low-cost
treatments, combined with other public health actions. Treatment of chronic non-communicable diseases, such as heart disease and diabetes and their sequelae, is costly, so prevention is a key strategy. Prevention and control of these diseases requires surveillance of associated behaviors and risk factors (e.g. smoking, physical inactivity, obesity) and actions to promote the desired changes and risk reductions.

Scarce resources for health make it is essential to evaluate interventions and target resources, so that their contribution is optimized, compared to other possible interventions. Surveillance can provide useful information to identify populations at greatest risk where intervention may help most, and to gauge the effectiveness of interventions.

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The Scope of Surveillance

The scope of surveillance is broad, from early warning systems for rapid response in the case of communicable diseases, to planned response in the case of non communicable diseases where the lag time between exposure and disease is longer than for communicable diseases. Most countries have laws or regulations on mandatory reporting of a list of conditions determined by each country, primarily communicable diseases such as childhood vaccine-preventable diseases (polio, measles, tetanus, and diphtheria), TB, hepatitis, meningitis, and leprosy. Reporting may be required also for non-communicable conditions, such as maternal deaths, injuries, and occupational and environmental diseases such as pesticide poisoning. Mandatory reporting of specific conditions is a subset of surveillance. International regulations (which are being revised) currently require reporting of three diseases to WHO: plague, yellow fever, and cholera.

A key principle is to include only conditions for which surveillance can effectively lead to prevention. Another important principle is that surveillance systems need to reflect the overall disease burden of the community. Other criteria for selecting diseases include: total number of cases, incidence and prevalence, indices of severity (eg, the case-fatality ratio), mortality rate and premature mortality, an index of lost productivity (eg, bed-disability days), medical costs, preventability, epidemic potential, and information gaps on new diseases.

Surveillance can collect data on any element of the disease causal chain—behavioral risk factors, preventive actions (vaccinations, pap smears), cases and program or treatment costs. The scope of a surveillance system is constrained by the available human and financial resources.

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Developing and Expanding a Surveillance System

The following table presents a possible scheme for developing a surveillance system. The minimal list of diseases is a starting point. Diseases should be added as the system evolves and resources become available. The table suggests a second line of diseases, but these will depend greatly on a country’s public health priorities, its disease burden, and the use of the data for intervention. A key principle of surveillance is that it is information for action. In some countries (eg Eastern Europe/Central Asia) non-communicable diseases are a large part of the disease burden, making risk factor surveillance even more important than tracking some specified diseases. A well developed system can include dozens of conditions for surveillance-third line.

Developing a surveillance system should build on success. It is best to start slowly, and demonstrate effectiveness, which builds support among those who report and use data and those who allocate resources. Being too ambitious initially may undermine enthusiasm for continued effort and be destructive.

Mandatory disease notification is the primary method of collecting timely disease information particularly for communicable diseases. Other surveillance methods include: sentinel surveillance sites, periodic or ongoing surveys, reporting by laboratories, special registers (eg cancer) and secondary analysis of datasets. Depending on circumstances, one or more of these methods may be the best choice.

Vital statistics are the foundation of health information and "the single most important addition that developing countries can make to their existing surveillance system" (White and McDonnell in Teutsch and Churchill 2000). Accurate records of all births and of deaths by cause are invaluable for monitoring trends, estimating the magnitude and understanding the distribution of conditions, and for tracking infant and maternal mortality. Electronic systems for reporting vital data are making this type of surveillance more timely and effective. Local health care providers can help ensure that births and deaths (by cause) are registered. There should be no fees for registering births and deaths. Incentives (requiring death certificates for burial, birth certificates for school enrolment and laws requiring registration) can improve vital statistic coverage.

Integrated disease surveillance is an effective, efficient and sustainable approach to strengthen national capacity for surveillance and response to communicable diseases. Surveillance activities for different diseases involve similar functions (detection, reporting, analysis and interpretation, feedback, action) and often use the same structures, processes and personnel. Yet in many countries surveillance is funded and managed by different independent control programmes. An integrated approach aims to establish a well co-ordinated, action oriented system that looks for opportunities to integrate functions where appropriate, maximize synergies, and build on successful initiatives. Where possible, countries should use a common reporting form, a single data entry system for multiple diseases, and common communication channels. Training and supervision should be integrated, a common feedback bulletin can be used, and computers and vehicles etc can be shared. Integrating surveillance for communicable and non-communicable diseases faces serious methodological issues: for example, different data collection methods are usually needed for CDs and NCD risk factors, but there is good potential for integrating the other aspects of surveillance.

Source:  World Bank, the Public Health Surveillance Toolkit
* The new International Health Regulations (2005) do not limit required reporting to these 3 diseases nor define what diseases must be reported.Instead they “… require States to notify WHO of all events that may constitute a public health emergency of international concern and to respondto requests for verification of information regarding such events.”
** Targeted for eradication

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Dos and Don'ts

• DO fully evaluate the existing system as part of project preparation or sector work to make things easier later. Involve national stakeholders in a team-based decision making process to determine the most appropriate and suitable surveillance model. This will help to ensure better data for decision-making, and establish ownership and commitment of key project implementers.

• DO carefully select a manageable, limited list of disease and risk factors for surveillance. Don’t include too many conditions for mandatory notification. Additional diseases and factors can be added once the system is running well and the data are being used effectively. Give priority to collecting and using vital statistics. Design a flexible system that can evolve and adapt to changing circumstances and country needs.
• DO set up a robust and accurate data transmission system, that allows data to be easily queried and corrected.
• DO ensure that the actors have a strong sense of ownership of the data and that core aggregate data on key indicators are transmitted and stored for use.
• DO build local ownership and commitment to the project. It is important to visit and engage sites outside of the national capital. Involve local and intermediate levels early on in decision-making (on design, roles and responsibilities) to ensure more successful outcomes. Include national professional associations and sectors other than health, which may also benefit from a good surveillance system (tourism, agriculture, treasury, and so on). Periodic dissemination of information to the press, and involving one or two health-related journalists might also bring advantages in promoting the project. Emphasize technical aspects and also the process as part of the strategy for building ownership.
• DO involve the private sector and the community in disease surveillance. DON’T rely entirely on the public health system as the sole source of information.
• DO create a detailed design of the investments for each level of the system. Pay close attention to what should be done at national, intermediate, and municipal levels of the system. Clearly define the roles and responsibilities of the three levels of the surveillance system. Avoid task overlap.
• DO as much design as possible while planning investments. A detailed implementation plan that identifies the task, its objectives, the location, starting date and ending date, the staff/entity responsible for implementation, a description of the main steps, unit cost and procurement procedures, and outputs is an important management tool for implementers and funders.
• DO ensure that surveillance guidelines specify "what and how, when, who and where" to survey. Guidelines should be revised by national health surveillance officials, externally reviewed, and the final product approved by key policy decision-makers.
• DO include the training necessary to develop competent and qualified personnel, who are absolutely fundamental to effective surveillance. Give high priority to training and capacity building.
• DO involve all stakeholders in the design of the system to help ensure that the information collected is used for making decisions on disease prevention and control.
• DO ensure necessary laboratory support for surveillance. Make sure that capacity and systems are in place to provide timely, reliable confirmation of suspected cases to those who will make decisions and take action.

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Key Reference

The Public Health Surveillance Toolkit, 80 pages of practical, specific, detailed information, and fundamental concepts in public health surveillance, that draws on the experience of World Bank staff, technical experts from PAHO and the CDC, and WHO references. Also provides selected key references and websites for additional information, and global and regional information on outbreaks and other surveillance data. http://www.worldbank.org/hnp > Tools &Guidelines

Other useful references

“Principles and Practice of Public Health Surveillance,” Teutsch SM and RE Churchill (eds) 2nd edition, 2000, New York, OUP

“Public Health Surveillance”, Halperin W, EL Baker, PR Monson (eds), 1992, New York, Van Nostrand Rienhold

http://www.who.int/csr WHO’s Communicable Disease Surveillance website

http://www.who.int/csr/resources/publications/csrpublications/en/index19.html for  for key WHO documents on surveillance:

• Protocol for the Assessment of National Communicable Disease Surveillance and Response Systems: Guidelines for Assessment Teams
• WHO recommended surveillance standards, 2nd edition http://www.who.int/ncd/surveillance site, especially see:
  • WHO Global NCD InfoBase
  • SuRF (Surveillance of Risk Factors) Report
  • WHO STEPwise approach to Surveillance of risk factors associated with non communicable diseases (STEPS)

People
World Bank: Marcelo Bortman (),
Anabela Abreu (),
Mariam Claeson (),
Isabella Danel (),
Joana Godinho (),
GNV Ramana (),
Daniel Miller ()

DHHS:  Steve Ostroff ()

CDC: Ray Arthur (),
David McQueen ()

WHO: Ruth Bonita (),
Guenael Rodier ()

PAHO:  Marlo Libel ()

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PDF Versions

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What are the sources of data for public health surveillance?

What are the types of surveillance systems?

What is surveillance system data?

What data are collected by a surveillance system?