What you need to know about the highly contagious delta variant

The delta variant has been replaced by omicron as the dominant strain in the United States, but health experts say it’s still cause for concern.

A health-care worker fills a syringe with a dose of Pfizer's coronavirus vaccine in Los Angeles on Wednesday, Aug. 11. (Robyn Beck/AFP/Getty Images)

The delta variant of the coronavirus has been overtaken by omicron — now the dominant strain in the United States.

In the fall, delta had been accounting for more than 99 percent of new cases of covid-19. But delta cases have virtually disappeared as omicron and its mutations made up 100 percent of infections the week ending March 5, according to data from the Centers for Disease Control and Prevention.

What to know about the omicron variant of the coronavirus

Many health experts had believed that any future “variant of concern” was likely to be a descendant of the delta variant. But the newest variant, known by the Greek letter omicron, is not a delta offspring, coming from a different portion of the virus’s family tree. It was identified in November in southern Africa and cases have since been confirmed in dozens of countries — including the United States.

CDC Director Rochelle Walensky has said that all three coronavirus vaccines available in the United States can provide strong protection against severe disease and death from covid-19, the disease caused by the virus, including the delta variant. However, vaccine effectiveness declined somewhat as the delta variant was surging — and early research suggests vaccines are less effective against omicron as well. Some of that decline may be because of the natural waning of antibodies, or because of changes in behavior as people have been less likely to wear masks or engage in social distancing.

Here are answers to common questions about the delta variant.

Coronavirus: What you need to know

End of the public health emergency: The Biden administration ended the public health emergency for the coronavirus pandemic on May 11, just days after WHO said it would no longer classify the coronavirus pandemic as a public health emergency. Here’s what the end of the covid public health emergency means for you.

Tracking covid cases, deaths: Covid-19 was the fourth leading cause of death in the United States last year with covid deaths dropping 47 percent between 2021 and 2022. See the latest covid numbers in the U.S. and across the world.

The latest on coronavirus boosters: The FDA cleared the way for people who are at least 65 or immune-compromised to receive a second updated booster shot for the coronavirus. Here’s who should get the second covid booster and when.

New covid variant: A new coronavirus subvariant, XBB. 1.16, has been designated as a “variant under monitoring” by the World Health Organization. The latest omicron offshoot is particularly prevalent in India. Here’s what you need to know about Arcturus.

Would we shut down again? What will the United States do the next time a deadly virus comes knocking on the door?

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