Ed Yong writes:

One of the few mercies during this crisis is that, by their nature, individual coronaviruses are easily destroyed. Each virus particle consists of a small set of genes, enclosed by a sphere of fatty lipid molecules, and because lipid shells are easily torn apart by soap, 20 seconds of thorough hand-washing can take one down. Lipid shells are also vulnerable to the elements; a recent study shows that the new coronavirus, SARS-CoV-2, survives for no more than a day on cardboard, and about two to three days on steel and plastic. These viruses don’t endure in the world. They need bodies.

But much about coronaviruses is still unclear. Susan Weiss, of the University of Pennsylvania, has been studying them for about 40 years. She says that in the early days, only a few dozen scientists shared her interest—and those numbers swelled only slightly after the SARS epidemic of 2002. “Until then people looked at us as a backward field with not a lot of importance to human health,” she says. But with the emergence of SARS-CoV-2—the cause of the COVID-19 disease—no one is likely to repeat that mistake again.

To be clear, SARS-CoV-2 is not the flu. It causes a disease with different symptoms, spreads and kills more readily, and belongs to a completely different family of viruses. This family, the coronaviruses, includes just six other members that infect humans. Four of them—OC43, HKU1, NL63, and 229E—have been gently annoying humans for more than a century, causing a third of common colds. The other two—MERS and SARS (or “SARS-classic,” as some virologists have started calling it)—both cause far more severe disease. Why was this seventh coronavirus the one to go pandemic? Suddenly, what we do know about coronaviruses becomes a matter of international concern.

The structure of the virus provides some clues about its success. In shape, it’s essentially a spiky ball. Those spikes recognize and stick to a protein called ACE2, which is found on the surface of our cells: This is the first step to an infection. The exact contours of SARS-CoV-2’s spikes allow it to stick far more strongly to ACE2 than SARS-classic did, and “it’s likely that this is really crucial for person-to-person transmission,” says Angela Rasmussen of Columbia University. In general terms, the tighter the bond, the less virus required to start an infection. [Continue reading…]