Five years ago this morning on Dec. 31, 2019, I was sitting at the kitchen table with a cup of coffee and my laptop. I was a member of “Flublogia,” a group of journalists, health scientists and kibitzers like me who had been tracking reports of disease outbreaks for years. I started every morning by checking my friends’ sites and Twitter feeds.

News had been slow lately; an Ebola outbreak in the eastern Democratic Republic of Congo was fading out. But this morning, several of my friends had picked up a report from Hong Kong’s Centre for Health Protection about a “cluster of pneumonia cases in Wuhan, Hubei province.”