Scientific American - USA (2022-05)

58 Scientific American, May 2022

T

he OmicrOn cOrOnavirus variant was likely the fastest-spreading virus in human

history. One person with the measles virus—a standout among infectious microbes—

might infect 15 others within 12 days. But when Omicron suddenly arrived this past

winter, it jumped from person to person so quickly that a single case could give rise

to six cases after four days, 36 cases after eight days, and 216 cases after 12 days. By

the end of February the variant accounted for almost all new COVID infections in the U.S.

Back when the Alpha variant was spotted in November 2020,

scientists knew little about how its few mutations would affect

its behavior. Now, with a year’s worth of knowledge and data,

researchers have been able to link some of Omicron’s 50 or so

mutations to mechanisms that have helped it spread so quickly

and effectively. That investigative process typically takes a lot

longer, says Sriram Subramaniam, a biochemist at the Univer-

sity of British Columbia. “But we’ve been looking at these vari-

ants for a year, so we were prepared,” he adds.

Omicron hosts twice as many mutations as other variants of

concern, and its BA.2 sublineage may have even more. There are

13 mutations on Omicron’s spike protein that are rarely seen

Megan Scudellari is a Boston-based science journalist

specializing in the life sciences.

E VA S I V E

A NAT OM Y

The Omicron coronavirus variant had specific mutations that hid

it from the immune system. That helped make it wildly contagious

By Megan Scudellari

Graphics by Veronica Falconieri Hays

VIROLOGY