Today’s society faces a paramount challenge from cyber-rumors that become rapidly viral and transform into more harmful impacts in social networks. The problem of cyber-rumors is further exacerbated in the health crisis context. In the healthcare literature, it has been well established that threat situations facilitate citizens’ behavior including cyber-rumor sharing. In this paper, we argue that in the healthcare context, both the threat attribute and cyber-rumor sharing are likely to be influenced by the proximity to health crisis. We argue that proximity is an important indicator of newsworthiness and shareworthiness in social media. In accordance, we investigate how the concept of proximity affects diffusion characteristics of cyber-rumor messages. We address the following research questions associated with cyber-rumor sharing in the context of Zika virus: How does proximity affect the threat appeal in a cyber-rumor message? How does proximity influence cyber-rumor sharing? The results indicate the negative effect of spatial and temporal distance on threat appeal, and the negative effect of spatial distance on cyber-rumor sharing. Such an investigation allows us to quickly identify the emergence of viral rumor messages and monitor the ongoing development of these messages in a timely manner.