Coronavirus Delta Variant Could Dominate In U.S. Within Weeks

The dangerous Delta variant of the coronavirus is spreading so quickly in the United States that it's likely the mutant strain will become predominant in the U.S. within weeks, according to a new analysis.

The variant, first identified in India, is the most contagious yet and, among those not yet vaccinated, may trigger serious illness in more people than other variants do, say scientists tracking the spread of infection.

The Delta variant apparently already accounts for at least 14% of all new infections, according to the research analysis posted online Monday of more than 242,000 infections nationwide over the last six months.

"It definitely is of concern," says William Lee, the vice president of science at Helix, which is under contract with the Centers for Disease Control and Prevention to help track the variants.

"Just the fact that it's so transmissible means that it's it's dangerous," Lee says, "and so I think you'll see outbreaks of Delta around the country and more people will get sick from it."

Helix launched the study when researchers spotted a drop in the prevalence of the Alpha variant, a contagious strain first spotted in the U.K. that had quickly become the dominant variant in that country and the U.S.

The researchers discovered the drop in relative frequency of the Alpha variant in their spot checks of strains circulating in the U.S. was due to a rapid increase in two other variants: the Gamma variant, first spotted in Brazil, and the Delta variant. The Gamma variant may be slightly better than the original strain at outmaneuvering the vaccines, researchers say.

"It looks like both of them are going to slowly push out Alpha," says Lee, whose study has not yet been peer-reviewed but has been posted on a pre-print server.

All the vaccines authorized for use in the U.S. appear, in general, to provide powerful protection against all the variants, including Delta. But the rapid spread of the variants is still raising concern because of the large number of people who remain unvaccinated. ...