T
he cleverest of enemies thrive on surprise attacks. Viruses—and coronaviruses in particular—know this well. Remaining hidden in animal hosts for decades, they mutate steadily, sometimes serendipitously morphing into more effective and efficient infectious agents. When a strain with just the right combination of genetic codes that spell trouble for people makes the leap from animal to human, the ambush begins.
Image: Illustration by Peter Greenwood for TIME
