Emergence of evidence during disease outbreaks: lessons learnt from the Zika virus outbreak

IntroductionOutbreaks of infectious diseases trigger an increase in scientific research and output. Early in outbreaks, evidence is scarce, but it accumulates rapidly. We are continuously facing new disease outbreaks, including the new coronavirus (SARS-nCoV-2) in December 2019.The objective of this study was to describe the accumulation of evidence during the 2013-2016 Zika virus (ZIKV) outbreak in the Pacific and the Americas related to aetiological causal questions about congenital abnormalities and Guillain-Barre syndrome. MethodsWe hypothesised that the temporal sequence would follow a pre-specified order, according to study design. We assessed 1) how long it takes before findings from a specific study design appear, 2) how publication of preprints could reduce the time to publication and 3) how time to publication evolves over time. ResultsWe included 346 publications published between March 6, 2014 and January 1, 2019. In the 2013--2016 ZIKV outbreak, case reports, case series and basic research studies were published first. Case-control and cohort studies appeared between 400-700 days after ZIKV was first detected in the region of the study origin. Delay due to the publication process were lowest at the beginning of the outbreak. Only 4.6% of the publications was available as preprints. DiscussionThe accumulation of evidence over time in new causal problems generally followed a hierarchy. Preprints reduced the delay to initial publication. Our methods can be applied to new emerging infectious diseases.