Is a variant worse than Delta on the way? Viral evolution offers clues.
Experts are exploring trends in the ways viruses mutate to understand why highly contagious variants like Delta emerge—and what might come next.
Somewhere in India last October, a person—likely immunocompromised, perhaps taking drugs for rheumatoid arthritis or with an advanced case of HIV/AIDS—developed COVID-19.
Their case might have been mild, but because of their body’s inability to clear the coronavirus it lingered and multiplied. As the virus replicated and moved from one cell to another, parts of the genetic material copied itself incorrectly. Maybe the person lived in a crowded home or went out to buy food in a busy market, but wherever it happened, the altered virus was spread to others. Experts believe this singular situation in one individual is likely how the Delta variant now wreaking havoc in the U.S. and around the world was born.
In the course of
