Fearing or fearsome Ebola communication? Keeping the public in the dark about possible post-21-day symptoms and infectiousness could backfire

US quarantine announcements do not include information that there is a moderate likelihood that Ebola-exposed people might exhibit symptoms, signalling infectiousness, beyond 21 days. As a result it is possible that if and when there is media coverage in the US of a delayed-symptom case, it might create citizen distrust in public health authorities and information and cause citizens to overestimate the risk of Ebola infection. In this article we report a research study which examined whether openness about post-21-day symptoms would attenuate negative reactions. We ran two experiments with online opportunity (Amazon mTurk) samples of Americans in late October-early November 2014, between the two deaths from Ebola in the US. In these experiments we assessed the reactions of respondents who saw quantitative estimates of post-21-day-symptom likelihood (n = 1413), or were informed about post-21-day symptoms with a rationale for the 21-day period after all saw a mock news story about a US case of 30th-day symptoms (n = 425). We found in both experiments that perceived risk increased and trust declined when people learned of post-21-day symptoms, and disbelief increased that 21 days without symptoms means no Ebola infection. In Study 2, informed persons and controls changed perceived risk and trust relative to baseline; test-group participants distrusted local medical personnel less and wanted shorter quarantines compared to controls who did not receive the information. Our findings suggest that informing Americans about the small likelihood of post-21-days Ebola symptoms would not increase perceived risk and distrust, and might diminish negative reactions to the media reporting a case who developed symptoms of Ebola after 21 days. Thus, public health officials wanting appropriate public responses to potential or actual epidemics may benefit from early communication of unpleasant infectious-disease facts before events reveal them, and signal officials’ lack of preparedness for public reactions.