In 2014, the world avoided a global outbreak of Ebola, thanks to thousands of selfless health workers — plus, frankly, some very good luck. In hindsight, we know what we should have done better. So, now’s the time, Bill Gates suggests, to put all our good ideas into practice, from scenario planning to vaccine research to health worker training.

Today the greatest risk of global catastrophe doesn’t look like this. Instead, it looks like this. If anything kills over 10 million people in the next few decades, it’s most likely to be a highly infectious virus rather than a war. Not missiles, but microbes.

There’s no need to panic … but we need to get going.