There is no time to waste. COVID-19 has started behaving a lot like the once-in-a-century pathogen. I hope it’s not that bad, but we should assume it will be until we know otherwise.

There are two reasons that COVID-19 is such a threat. First, it can kill healthy adults in addition to elderly people with existing health problems. The data so far suggest that the virus has a case fatality risk of around 2.4%; this rate would make it many times more severe than typical seasonal influenza-like the 1957 influenza pandemic (0.6%) and the 1918 influenza pandemic (2%).

Second, COVID-19 is transmitted quite efficiently. The average infected person spreads the disease to two or three others — an exponential rate of increase. There is also strong evidence that it can be transmitted by people who are just mildly ill or even presymptomatic. That means COVID-19 will be much harder to contain than the Middle East respiratory syndrome (MERS) or severe acute respiratory syndrome (SARS), which were spread much less efficiently and only by symptomatic people. In fact, COVID-19 has already caused 10 times as many cases as SARS in a quarter of the time.

National, state, and local governments and public health agencies are taking serious steps to slow the virus’s spread. The world also needs to accelerate work on treatments and vaccines for COVID-19. Drug discovery can also be accelerated by drawing on libraries of compounds that have already been tested for safety and by applying new screening techniques, including machine learning, to identify antivirals that could be ready for large-scale clinical trials within weeks.

All these steps would help address the current crisis. But we also need to make larger systemic changes so we can respond more efficiently and effectively when the next epidemic arrives.