What to know about the COVID-19 delta variant

In addition to urging that even vaccinated people in certain parts of the country wear masks while indoors, the CDC also wants everyone in a K-12 school to mask up indoors, regardless of where the school is and regardless of vaccination status.

Every state saw more coronavirus cases in the past week than in the prior week, CNN reported, saying the United States has averaged about 57,000 new cases every day over the week. The nation reached a low for 2021 of 11,351 cases on June 22.

According to unpublished data, even though vaccination prevents infection in most cases, those who do get infected with the delta variant have as much virus in their bodies as those who are unvaccinated, the CDC reported. While a vaccinated person who becomes infected is almost certainly protected from a bad case of COVID-19 and death, that person can still spread it.

It’s more infectious and less responsive to medicine such as monoclonal antibody treatments, according to the CDC. In a study published July 7, researchers found that the viral loads in COVID-19 delta infections were about 1,000 times higher than in earlier strain infections, on the day the virus was first detected.

Dr. Rochelle Walensky, the CDC director, said July 8: "Although we expected the delta variant to become the dominant strain in the United States, this rapid rise is troubling. We know that the delta . . . is currently surging in pockets of the country with low vaccination rates."

Coronaviruses are like other viruses — they change based on trial and error, evolving on a microscopic level at the edge of life. Viruses invade the body and make numerous copies of themselves — their survival mechanism. Sometimes the copies are akin to the origin, sometimes they are inferior, but sometimes they are superior — and those superior copies thrive and go on to infect other hosts. The superior copy may be more efficient at infecting a person, at resisting medicine, at making a person sicker.

It was first detected in India. According to the World Health Organization, it is now in at least 85 countries. According to the CDC, it’s the variant in most recent coronavirus cases here — 83%.

By June, the version of the initial coronavirus from late 2019 that was identified in Wuhan, China, was no longer the dominant one. The D614G mutation, which had been identified in late January or early February 2020, was.

There’s also the B.1.1.7 — first identified in the United Kingdom — that was first detected in September. That variant spreads quickly and more easily than others and has been detected in North America and elsewhere

And there’s one linked to South Africa, called B1.351, and another to Brazil, called P.1.

Pfizer and its collaborator BioNTech, which make one of the three U.S.-approved vaccines, have announced plans to seek authorization within weeks from federal regulators to authorize a booster shot of the coronavirus vaccine to combat the delta variant, according to the news agency Reuters. The firms cite the variant’s spread and the greater infection risk six months after vaccination. But in a joint statement issued in response, the CDC and Food and Drug Administration said that people who have been fully vaccinated don’t need a booster.

Johnson & Johnson, which makes another approved vaccine, said July 1 that "its single-shot COVID-19 vaccine generated strong, persistent activity against the rapidly spreading delta variant and other highly prevalent SARS-CoV-2 viral variants."

The other approved vaccine in the United States is made by Moderna, and that company said June 29 that its shots "produced neutralizing titers against all variants tested," including the delta variant.

Research is still being done, but the website of the nonprofit The Conversation said: "While fever and cough have always been common COVID symptoms, and headache and sore throat have traditionally presented for some people, a runny nose was rarely reported in earlier data [from before the delta variant emerged]. Meanwhile, loss of smell, which was originally quite common, now ranks ninth."

That might be because reports of symptoms were originally coming from hospitals, where people were likely to be sicker and older, or because of how the virus has changed, the website said.