Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, listens during a press conference in the James S. Brady Press Briefing Room at the White House in Washington, DC on Tuesday, April 13, 2021.

Leigh Vogel | Bloomberg | Getty Images

White House senior medical advisor Dr. Anthony Fauci said Tuesday the highly contagious Delta variant is the “greatest threat” to the nation’s attempt to eradicate Covid-19.

Delta, which was first identified in India, now accounts for about 20% of all new cases in the United States, up from 10% about two weeks ago, Fauci said during a White House press conference on the pandemic.

He said Delta appears to be “following the same pattern” as Alpha, the variant first found in the UK, with infections doubling in the US about every two weeks.

Fauci’s comments come after CDC director Dr. Rochelle Walensky on Friday urged Americans to get vaccinated against Covid and said she expected Delta to become the dominant coronavirus variant in the United States

Studies suggest that it is about 60% more transmissible than alpha, which was more contagious than the original strain that emerged from Wuhan, China, in late 2019

“As worrying as this Delta strain is about its hypertransmittance, our vaccines are working,” Walensky told ABC’s Good Morning America. If you get vaccinated, “you will be protected against this Delta variant,” she added.

In the UK, the Delta variety recently became the dominant variety there, surpassing Alpha, which was first discovered in the country last fall. The Delta variant now accounts for more than 60% of new cases in the UK

Fauci said Tuesday the US had “the tools” to defeat the variant and urged more Americans to get a full Covid vaccination.

The Biden administration said Tuesday that it is unlikely to meet President Joe Biden’s goal of getting 70% of American adults to receive one or more vaccinations by July 4th.

“The effectiveness of the vaccines in this case two weeks after the second dose of Pfizer-BioNTech was 88% against Delta and 93% against Alpha for symptomatic diseases,” said Fauci, citing a study.

The World Health Organization said Friday that Delta is becoming the predominant variant of the disease worldwide.

On Monday, WHO officials warned that the variant was the fastest and strongest coronavirus strain to date and that it would “pick up” the most vulnerable people, especially in places with low Covid-19 vaccination rates.

It has the potential to be “more deadly because it is more efficient in the way it is transmitted between people, and it will eventually find those at risk who will become seriously ill, hospitalized and possibly die”, Dr. Mike Ryan, executive director of WHO’s Emergency Health Program, said during a news conference.

This is a developing story. Please check again for updates.