https://www.wired.com/story/covid-19-is-nothing-like-the-spanish-flu/

Coverage of the novel coronavirus pandemic teems with monstrous and sometimes contradictory statistics. Among the most vexing figures flitting across our screens, and spreading via text and Tweet, is the case fatality rate (CFR)—the proportion of known infections that result in death. Early in the Covid-19 pandemic, World Health Organization officials announced an average CFR of 2 percent. Later on, they revised it up to 3.4 percentt. In contrast, numerous epidemiologists have argued that the global case fatality rate is closer to one percent. These might seem like small differences, but when multiplied across large populations they translate to significant discrepancies in overall deaths.

Some experts have emphasized the difficulty of calculating the fatality rate of an emerging pandemic, explaining that current estimates are biased by a deficit of testing and by the lag time between onset of illness and death. Despite this counsel, news coverage and social media discourse has obsessed over CFRs and how they compare across pandemics throughout history. A popular refrain is that the new coronavirus has a frighteningly high fatality rate of at least two percent, which is supposedly comparable to that of the 1918 influenza pandemic, also known as the Spanish flu—one of the deadliest viral outbreaks in history. The truth is that this comparison is severely flawed and that the numbers it relies on are almost certainly wrong.