There’s not yet consensus on whether the Delta variant makes people sicker. Does the Delta variant cause more serious disease? “That might potentially explain why it’s able to transmit much more efficiently and why the viral loads are so much higher, although other mutations that Delta accumulated could very well contribute also,” said Roan. Unpublished studies suggest that the original virus primes about 50 percent of its viruses, whereas the Delta variant primes more than 75 percent. This site is important for “priming” or activating newly replicated viruses to begin infecting cells. Of particular note, said Roan, is a spike protein mutation at what’s known as the furin cleavage site. We know that the Delta variant carries multiple mutations, including within the spike protein which it uses to latch onto and enter cells. That efficiency comes down to the molecular details. “Not only is it replicating more, it’s replicating faster, and that’s probably why it’s able to spread so much more efficiently,” said Roan. That study also found that people infected with the Delta variant carry detectable virus earlier than with the original virus (four days versus six days after exposure) and another study found that they remain infectious longer (18 days versus 13 days). A study from China reported that people infected with the Delta variant can carry 1,000 times the viral load as those infected with the original virus. Its high infectiousness could be due to its ability to replicate rapidly in the body. How much more infectious is the Delta variant? How is it able to do that?Īccording to an internal CDC document, the Delta variant – one of four “variants of concern” that have evolved from SARS-CoV-2, the virus that causes COVID-19 – is more than twice as infectious as the original virus and as infectious as chickenpox.ĭenise Barchas, RN, works in the ICU respiratory isolation room at UCSF Mount Zion Medical Center. We spoke to virologist Nadia Roan, PhD, associate professor at UC San Francisco and associate investigator at the Gladstone Institutes, about the latest developments in our knowledge of the Delta variant. We are only beginning to understand how the new variant spreads so efficiently, whether it causes more serious illness, and why there are more breakthrough infections as Delta spreads. While experts agree that the vaccines still offer strong protection against infection by the Delta variant, and especially against severe illness and death, questions remain. Last week, the Centers for Disease Control and Prevention recommended that fully vaccinated people in areas of high transmission return to masking in public indoor spaces, citing evidence that the Delta variant can produce high viral loads in the noses and throats of even the fully vaccinated.
The highly infectious Delta variant was first detected in India in March, and it now accounts for more than 93 percent of sequenced coronavirus cases nationwide. The Delta variant is fueling COVID-19 cases across the U.S., and raising questions about what this all means for the course of the pandemic. Photo by Barbara Ries.īreakthrough infections.
Jesse Demings, with the UCSF Black Health Initiative, invites local residents to get vaccinated.
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