Yet such data on patients isn’t being streamlined and shared with the public quickly. There are shortcomings in our ability to access the electronic systems designed to help glean facts from clinical data. CDC hasn’t been filling its traditional role of promptly publishing medical findings that may help doctors care for patients. Instead, a lot of this information is being passed around social media, by email or even through word of mouth. It’s trial and error on a global scale.

To take one example, the latest evidence is that blood clots are a frequent complication of Covid. The disease seems to activate platelets in ways that doctors are only beginning to untangle. It’s likely that some patients who seemed to need ventilators to breathe instead developed big clots in their lungs. This finding is supported by autopsy data that emerged this month. Studies from the Netherlands and France suggest that clots arise in 20% to 30% of critically ill Covid patients. For weeks, American doctors have been experimenting with blood thinners to stave off these complications.

Another insight: Patients can appear to be starved for oxygen—say, a pulse oximeter reading in the 80s when a reading below 94% might normally suggest trouble—even though their organs are in fact well supplied with air. Doctors have become more conservative in putting patients on breathing machines and are trying novel ways of providing ventilator support, such as prone positioning. The traditional way providers have used respirators can damage lungs that are inflamed from infection.