Public-health leaders and scientists are now mining the lessons of Covid-19 for strategies to avert the next one. Smarter lung scans and screening of blood samples are two of their ideas. They also are working on new tools and approaches to find infections before they spread, to choke off budding outbreaks, to respond quickly with better public-health systems, drugs, vaccines, and to improve global cooperation and strengthen the WHO.

To do that, they say nations need to invest in preparing for epidemics the way they prepare for war or any other threat to national defense—with steady funding, accepting the spending as a necessary cost of keeping society safe even when there is no epidemic.