Signal-Oriented Framework for Early Identification of Imported Respiratory Infectious Disease Risk

Increasing international travel and population mobility have made surveillance of imported infectious diseases more complex. However, current approaches still rely largely on confirmed epidemiological evidence and retrospective analyses of importation events. Their limited capacity to integrate heterogeneous information constrains early identification of emerging importation risks. Drawing on signal analysis theory, we developed a conceptual and operational framework for early identification of imported respiratory infectious disease risks involving human-to-human transmission. The framework conceptualizes imported disease risk as a dynamic process in which underlying risk factors generate observable surveillance indicators and event-based information that are progressively transformed into candidate risk signals, risk signals, and warning signals. We established an operational workflow comprising signal collection, integration, assessment, and escalation to organize heterogeneous evidence across the importation pathway. The framework incorporates four complementary domains: pathogen characteristics, overseas epidemic situation, cross-border importation risk, and post-entry transmission risk. These domains provide structured inputs for signal identification and assessment. Risk signals are evaluated according to signal characteristics, epidemiological stage, and consequence severity; they may be escalated to warning signals when predefined evidence and priority criteria are met. This framework provides an operational approach for integrating weak and heterogeneous information before importation events are fully confirmed, supporting earlier risk recognition and public health decision-making.