BACKGROUND: In times of a public health emergency such as COVID-19, a government-centric approach may not be sufficient to contain the epidemic and ensure citizens' compliance. This study proposes a theoretical model that integrates individual-oriented, social-oriented, and community-oriented factors to predict individuals' engagement in preventive behaviors and citizen health emergency communication (CHEC). Perceived shared responsibility, which results from the communal nature of the pandemic, is tested as a mediator in the relationships between different motivations and behaviors in the context of COVID-19. METHOD: To test the model, an online survey with a quota sample of 1,301 adults reflecting the composition of the U.S. population was conducted via Qualtrics. RESULTS: Results show that perceived severity, self-efficacy, worry, and social support significantly increase the perception of shared responsibility, subsequently increasing individuals' adherence to preventive behaviors and their engagement in CHEC. In this process, shared responsibility serves as a mediator between some tested relationships between motivators and two types of behaviors (i.e. communication and prevention). CONCLUSIONS: During a public health emergency, individuals' preventive behaviors and communication behaviors are determined by the individual-oriented (e.g. perceived severity), social-oriented (e.g. social support), and community-oriented (e.g. perception of shared responsibility) factors. In this mechanism, the perception of shared responsibility explains how some motivators influence individuals' communication and prevention behaviors.