Outbreaks of publications about emerging infectious diseases: the case of SARS-CoV-2 and Zika virus

SummaryBackgroundOutbreaks of infectious diseases generate outbreaks of scientific evidence. In 2016 epidemics of Zika virus emerged, largely in Latin America and the Caribbean. In 2020, a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a pandemic of coronavirus disease 2019 (COVID-19). We compared patterns of scientific publications for the two infections over time.MethodsWe used living systematic review methods to search for and annotate publications according to study design. For Zika virus, a review team performed the tasks for publications in 2016. For SARS-CoV-2, a crowd of 25 volunteer scientists performed the tasks for publications up to May 24, 2020. We used descriptive statistics to categorise and compare study designs over time.FindingsWe found 2,286 publications about Zika virus in 2016 and 21,990 about SARS-CoV-2 up to 24 May 2020, of which we analysed a random sample of 5294. For both infections, there were more epidemiological than laboratory science studies. Amongst epidemiological studies for both infections, case reports, case series and cross-sectional studies emerged first, cohort and case-control studies were published later. Trials were the last to emerge. Mathematical modelling studies were more common in SARS-CoV-2 research. The number of preprints was much higher for SARS-CoV-2 than for Zika virus.InterpretationSimilarities in the overall pattern of publications might be generalizable, whereas differences are compatible with differences in the characteristics of a disease. Understanding how evidence accumulates during disease outbreaks helps us understand which types of public health questions we can answer and when.FundingMJC and HI are funded by the Swiss National Science Foundation (SNF grant number 176233). NL acknowledges funding from the European Union’s Horizon 2020 research and innovation programme - project EpiPose (grant agreement number 101003688). DBG is funded by the Swiss government excellence scholarship (2019.0774) and the Swiss School of Public Health Global P3HS.