Creating misinformation: how a headline in The BMJ about covid-19 spread virally

The spread of the novel coronavirus has been accompanied by a viral spread of misinformation. Misinformation is easily created, as shown by a recent news story in The BMJ about a preprint, claiming that “a third of covid-19 patients admitted to UK hospitals die.”1 On Twitter, The BMJ added “putting the fatality rate on par with Ebola,” on the basis of a quote from one of the study’s authors. Unsurprisingly, this generated news headlines such as “Experts warn coronavirus ‘as dangerous as Ebola’ in shocking new study.”2

Covid-19’s case fatality rate (CFR)—the ratio between confirmed deaths and confirmed cases—has a current global average of around 6.5%.3 Given diagnostic testing constraints and substantial under reporting of cases globally, covid-19’s true infection fatality rate is probably much lower. Ebola’s CFR is, on average, 50%—every second patient with confirmed Ebola will probably die.4 Simply comparing CFRs, covid-19 is obviously less fatal than Ebola.

The preprint, however, analysed covid-19’s hospital fatality rates (HFR): the death rate among the subset of cases severe enough to require hospitalisation. For covid-19, hospitalised cases comprise only a small proportion of total cases (although the exact proportion globally remains unclear). For Ebola, almost all patients need hospital care: the CFR is roughly similar to the HFR. Comparing covid-19’s HFR to Ebola’s CFR is uninformative at best, misleading at worst.

Combining Ebola and covid-19 in a single sentence is an effective way to get public attention but is not an effective strategy to communicate scientific information, particularly when public fear and anxiety are high. Misinformation is often a technically correct fact that is taken out of context, creating a narrative on its own.5 Every piece of emerging evidence deserves to be reported with due care—especially if it is published by a credible source such as a leading medical journal.