Preprints — scientific manuscripts that are posted at a recognized online repository before peer review — have the potential to speed up the reporting of scientific research in infectious disease outbreaks, argue Michael Johansson and colleagues in an Essay in PLOS Medicine: "The scientific community should not ask why preprints are posted during outbreaks, we should ask why they are not posted…."

Before publication in journals, scientific research papers in many disciplines are assessed by peer review, in which experts provide detailed criticisms and advise editors on suitability for publication.

Although peer review is viewed as an important way to improve research methods and ensure the validity of scientific publications, the process can be time-consuming and may involve subjective judgments regarding novelty and journal scope.

Publicly shared preprints can permit other researchers to provide constructive criticism and use the data and findings to further their own research as appropriate. Peer review for traditional publication can follow or occur concurrently.

In February 2016, in the wake of the major Ebola outbreak in West Africa and early in the Zika epidemic in the Americas, leading funding agencies and journals issued a statement about the importance of data sharing and preprint posting in infectious disease outbreaks.

Johansson and colleagues assessed preprints and publications relevant to the outbreak of Ebola, which occurred before the statement, and the Zika epidemic, which continued over the months following the statement.

They note that preprint posting increased for Zika relative to Ebola and provided much earlier access to scientific findings, but was used for only a small proportion of papers.

Based on their analyses, Johansson and colleagues advocate the broader use of preprints to provide early access to scientific reports and permit criticism, analysis and further studies by other researchers in infectious disease outbreaks.

The authors also note that mechanisms are needed to ensure that preprints meet high standards of ethics oversight and reporting, and that preprints should be included in evaluations of researchers' academic records.