Devaraj

One of the key reasons the Delta variant has ignited new surges of Covid-19 infections across the United States is its remarkable ability to make copies of itself. That skill has helped make Delta far more transmissible than any other iteration of the coronavirus seen thus far. But its replication prowess could also be at the heart of the other twists Delta has thrown into the pandemic, including the increase in breakthrough infections with the variant and why it potentially causes severe Covid-19 more often. Delta’s breakneck proliferation isn’t its only trick tied to the increase in infections — and symptomatic infections — in people who’ve been vaccinated. With the mutations the variant picked up as it evolved, it can partially cloak itself from the immune system’s antibodies. That gives the variant a better chance of sneaking past that first line of defense to start an infection compared to earlier forms of the virus. (The vaccines, however, haven’t lost any significant step in protecting against severe outcomes from the coronavirus. They are also still preventing many infections entirely.But experts say a crucial factor in Delta’s spread even to vaccinated people is that those infected with the variant seem to be “shedding” comparatively massive amounts of virus, exposing others to much higher levels. An oft-cited statistic is that, with Delta, people have 1,000 times as much virus in their upper airways early on in their infections compared to with the strain that emerged in China in 2019. Some experts quibble with that exact estimate, but the point remains that people who contract Delta have lots more virus in their noses and throats, and are in turn emitting lots more virus. That influx of virus into others’ airways seems to be able to overwhelm the antibodies that aim to guard the cells from infection.