Linking human behaviors and infectious diseases.

Human behaviors determine outbreak trajectories of infectious diseases. This fundamental relationship underlies why broad behavioral interventions (BIs) are effective tools in outbreak management. BIs target an overall reduction in contacts and behaviors that enable pathogen transmission as a nonspecific solution for preventing new infections. Despite that, there is a lot that remains unknown about the interactions between human behavior and infectious diseases. These gaps limit targeted outbreak management and prevention. In PNAS, Vigfusson et al. (1) narrow this gap by exploring multiple ways to assess behavioral changes in infectious hosts using existing data sources. By linking mobile-phone call detail records (CDRs) with health records of clinically confirmed influenza, they measure deviations in routine behaviors during illness compared to pre- and postillness behaviors. There are many well-studied links between human behavior and infectious diseases. The concept of the behavioral immune system posits that susceptible individuals exercise preventative behaviors when faced with the threat of infection (2). Disease avoidance saves the immune system from the costly process of reacting to the invasion of a pathogen. These behaviors include reactions like disgust and avoidance of infectious hosts. Other individual behaviors linked to epidemiological outcomes are correlated with exposure and infection. For example, higher social activity is linked to an increased likelihood of influenza infection during outbreaks (3). At larger scales, synchronized movements among susceptible individuals that increase population density and contacts can drive population-wide disease outbreaks (4, 5). Human behaviors linked to active infections have been more difficult to characterize. Asymptomatic or mildly symptomatic individuals can be central to superspreading events because behaviors do not change during a period of infectiousness (6, 7). For symptomatic infections in humans, disease modelers and policy makers often assume that hosts have fewer contacts or move less than healthy hosts (5), but data explicitly … [↵][1]1Email: nita{at}psu.edu. [1]: #xref-corresp-1-1