GoingMadlem

As epidemiologist @EpiEllie explains, it's almost certainly just "lead time bias." That's when you test more people, including presymptomatic people, and thus discover the disease earlier than before. https://twitter.com/EpiEllie/status/1280305393516904448 … 2/

That means we learn people are sick earlier, which means that the time between detection and death gets longer - not because people are surviving longer from the onset of symptoms, but because we're detecting sick people before they exhibit symptoms. 3/

Lead-time bias emerges whenever we ramp up testing: routine mammograms and colonoscopies appeared to change the course of related cancers, but what was really going on was earlier, presymptomatic identification of cancers. 4/

And while it's true that we measured earlier cases from the first symptoms, we didn't know what some symptoms were (loss of smell, for example) and we relied on self-reporting by gravely ill people, which isn't as good as actual tests. 5/