Emerging and re-emerging infectious diseases continue to challenge public health systems worldwide. In recent years, expanding surveillance networks, advances in pathogen detection, genomic sequencing, artificial intelligence, and the integration of multiple data sources have greatly improved the ability to detect unusual signals at an early stage.
Yet detecting a signal is only the beginning.
Between the first sign of an unusual event and an effective public health response lie several critical steps: verifying the signal, identifying the pathogen, assessing the risk, making a decision, and translating that decision into action. Delays at any point can narrow the window for effective control.
A new Perspective published in Science Bulletin examines this persistent gap between risk assessment and public health action. Researchers from the Beijing Center for Disease Prevention and Control and collaborating institutions ask a practical question: how can infectious disease risk assessment better support timely and actionable public health decisions?
The authors argue that risk assessment should not be treated as a stand-alone technical exercise. Instead, it should be embedded throughout the process of outbreak detection and response, serving as the link between emerging evidence and real-world action.
Early in an outbreak, however, information is rarely complete. Key characteristics of a new threat, including its transmissibility, severity, routes of transmission, affected populations, and potential for wider spread, may still be uncertain. A complete and definitive assessment is therefore often impossible when decisions are most urgently needed.
For this reason, the authors emphasize that risk assessment should be viewed as a dynamic and iterative process rather than a one-time judgement. Initial assessments should be made using the best evidence available at the time, then updated as epidemiological investigations, laboratory testing, pathogen characterization, genomic data, and evidence of transmission accumulate.
The Perspective proposes a framework that follows the full pathway from signal detection, verification and pathogen attribution, through risk assessment and decision-making, to operational response and adaptive control. Risk assessment sits at the center of this pathway, connecting surveillance information with decisions about what should happen next.
The authors identify four recurring weak points that can prevent this pathway from functioning effectively.
The first is delayed verification of unusual signals.
A change in a single surveillance indicator does not necessarily indicate a new public health threat. Signals need to be verified quickly and interpreted alongside other evidence. This can be particularly difficult in settings with limited laboratory and surveillance capacity, where case investigations, diagnostic testing, and pathogen identification may be delayed.
The authors argue that faster verification requires earlier integration of epidemiological, laboratory, genomic, and other relevant information. Strengthening diagnostic capacity in areas where surveillance is weaker, while using multiple sources of evidence to cross-check unusual signals, can help shorten the interval between detection and confirmation.
The second is risk assessment cannot ignore context.
The public health impact of an infectious disease is determined not only by its transmissibility or severity. It also depends on the population and setting in which transmission occurs.
Population susceptibility, previous immunity, social contact patterns, population mobility, health-care capacity, and the ability of local systems to mobilize resources can all substantially alter the consequences of the same pathogen. The same infectious disease may therefore pose very different risks across countries, regions, or population groups.
Risk assessment should consequently be context-sensitive, taking into account characteristics of the pathogen, the exposed population, the surrounding environment, and the capacity of the health system. These assessments should also be revised as the epidemiological situation changes.
The third is the lack of a clear connection between risk levels and response measures.
Risk assessments frequently classify threats using terms such as low, moderate, or high risk. But these categories are of limited operational value if decision-makers do not know what actions should follow from them.
The article argues for clearer links between risk indicators, assessed risk levels, and specific response options. Depending on the scenario, predefined triggers could be linked to actions such as intensified surveillance, expanded diagnostic testing, mobilization of emergency resources, protection of high-risk populations, or activation of cross-sector coordination.
Such an approach could make risk assessment more directly useful for decision-making by clarifying not only how serious a situation may be, but also when and how the response should change.
The fourth is the gap between deciding what should be done and being able to do it.
Even a scientifically sound risk assessment will have limited value if the recommended response cannot be implemented rapidly.
Laboratory capacity, health-care resources, emergency supplies, trained personnel, interagency coordination, and risk communication all influence whether decisions can be translated into effective action. The authors therefore argue that improving risk assessment tools should go hand in hand with strengthening operational preparedness.
This means testing not only whether a risk assessment framework can identify a threat, but also whether health systems have the capacity to act on its conclusions.
Across all four stages, timely data sharing, clearly defined responsibilities, coordination, trust, and accountability are essential enabling conditions. New evidence should continuously feed back into the assessment process so that both the estimated level of risk and the response can be adjusted as the situation evolves.
Most early decisions during an emerging infectious disease event must be made before all the evidence is available. The value of risk assessment is therefore not to wait until uncertainty has disappeared. It is to provide the best possible basis for decisions using the evidence available at that moment, while making uncertainty explicit and revising conclusions as new information emerges.
Closing the gap between surveillance signals, risk judgement, and public health action could shorten the time from detecting an unusual event to initiating an appropriate response. For emerging and re-emerging infectious diseases, the authors argue, this connection may be as important as improving detection itself.
Science Bulletin