Category:Epidemic intelligence: Difference between revisions

Epidemic intelligence is the systematic detection, verification, analysis, and communication of information about events that may pose a threat to public health. It integrates two complementary components: indicator-based surveillance and event-based surveillance. Both aim to detect public health threats as early as possible and to monitor known threats until they are resolved. Epidemic intelligence covers both risk assessment and risk monitoring.

Components of epidemic intelligence

Indicator-based surveillance refers to structured data collected through routine surveillance systems. These systems gather predefined indicators on identified risks, emerging risks, and non-human health-related risks (such as environmental or zoonotic factors).

Event-based surveillance refers to unstructured information gathered from formal and informal sources, including official reports, the media, scientific publications, and rumours circulating at national or international level.

The two components are complementary. Indicator-based surveillance provides continuous, comparable data on known threats over time. Event-based surveillance enables rapid detection of unexpected or emerging threats that structured systems may miss, often before they are captured by routine reporting.

Signals and events

A frequent source of confusion in epidemic intelligence is the distinction between a signal and an event.

A signal is a piece of raw information emerging from screening of formal or informal sources — a news item, a rumour, a hospital alert, an entry in a scientific publication — that may indicate a public health concern but has not yet been assessed for relevance or accuracy. Signals are abundant, frequently irrelevant, and often unverified.

An event is a signal (or cluster of signals) that has passed filtering and is judged to be potentially relevant to public health: for example, an unexplained cluster of illness, an unusual outbreak, or a reported hazardous exposure. An event is a hypothesis worth investigating, but it is not yet confirmed.

A validated event is an event that has been cross-checked against official or otherwise reliable sources and confirmed to be both real and adequately characterised. Only validated events proceed to risk analysis.

In short, the process is a funnel of decreasing volume and increasing confidence: raw inputs are screened into signals, signals are filtered into events, and events are validated before analysis.

The epidemic intelligence process

Epidemic intelligence aims to produce timely, validated, and actionable intelligence on events related to communicable diseases — or to disease of unknown origin — that are of interest to public health authorities. The process can be divided into the early detection of new threats and the monitoring of threats already identified, including potential threats.

Early detection

Early detection comprises six elements:

1. Screening news, official reports, notes, and rumours from a defined (e.g. European) perspective in order to identify meaningful signals, using predefined criteria.
2. Filtering the signals to retain only those that represent potential public health events of interest.
3. Validating events originating from unofficial sources by cross-checking against official or otherwise reliable sources, to confirm that the event is real and adequately understood.
4. Analysing the validated event to capture the full picture, including epidemiological data, exposure information, and contextual factors.
5. Assessing the risk associated with the event on the basis of the analysis (see risk assessment).
6. Communicating and documenting the identified threats. This element runs throughout the previous five steps and includes dissemination via ad-hoc communications, daily bulletins, and weekly bulletins.

Monitoring identified threats

Monitoring is the active follow-up of all information directly relevant to an identified threat. It is an iterative process that continues until the threat is considered to have subsided or until all appropriate public health measures have been implemented.

Practical considerations

In a rapidly evolving situation, professional judgement is essential. Under severe time constraints it may be appropriate to skip or compress some of the steps above in order to share information quickly. However, when epidemic intelligence is gathered systematically as described, the outcome is a better-informed decision and more effective action.