The novel coronavirus is devious, persistent, and, according to some scientists, not even alive. But, as the world has had to learn, this tiny bundle of genetic material is a highly efficient invader. Each particle is armored with roughly 100 protrusions, or spikes, perfectly evolved to latch onto an enzyme on the surfaces of throat and lung cells, then slip into them and replicate millions and millions of times.
Older coronaviruses, such as the one that caused severe acute respiratory syndrome, or SARS, operated similarly. The spikes of the new coronavirus, though, clasp human cells much more tightly, which appears to be one reason it spreads more easily. In the three months since scientists in China identified it, the coronavirus has infected more than 2.4 million people around the world and killed at least 165,000.