Public health officials are keeping tabs on this new mutation of the Delta variant.


As the super-transmissible Delta variant marches across the US, mutant versions are developing. Among the latest iterations giving the world's public health officials pause is AY.1, also known as "Delta-plus."

COVID-19 variants can come and go. So is Delta-plus a mutation to worry about? Here's what we know so far.

Credit: Getty Images / Jo Imperio

What is Delta-plus?

Human coronaviruses are named for the crown-like spikes that surround the virus. SARS-CoV-2, the virus that causes COVID-19, is no exception. It's covered in spike proteins that help the virus enter healthy cells.

The Delta-plus variant carries a specific spike-protein mutation called K417N. According to the Washington Post, that same mutation has been found in some substrains of Alpha, which had been the dominant strain in the US this spring until Delta took hold.

"Interestingly enough, this exact same mutation appeared in the Beta variant, and the Beta variant has been out-competed by the Delta variant," Kenneth Stedman, PhD, professor of biology at Portland State University in Oregon, tells Health. "So it may turn out that Delta-plus is actually worse than Delta. We don't know."

Where did Delta-plus originate?

First identified in Europe in March, Delta-plus has since been found in several other counties, including the US, per Washington Post reporting.

In a technical briefing published in June, Public Health England noted that routine scanning of the Delta variant led to the detection of a small number of genomic sequences with the K417N spike protein mutation.

India's health ministry classified AY.1 as a "variant of concern" in June, per the BBC. That designation indicates that it's more transmissible, binds more easily to lung cells, and is potentially resistant to monoclonal antibody therapy, the news organization reported.

Public health officials in South Korea have detected the country's first two cases of Delta-plus, Reuters reported earlier this week.

Is Delta-plus circulating in the US?

At present, Delta-plus accounts for a tiny fraction of COVID cases in the US: just 0.1%, per data released Wednesday by the US Centers for Disease Control and Prevention (CDC).

However, Delta remains the dominant variant in the US. If you count all of its sublineages (including its AY.1, AY.2, and AY.3 mutations), Delta is responsible for an estimated 93% of COVID cases in the US, according to CDC data.

With cases on the rise across the nation, concerns about the Delta variant have already led to new masking recommendations and ICU bed shortages in COVID hot spots. An internal CDC document obtained by the New York Times last week indicated that Delta is just as contagious as the chickenpox and more transmissible than the viruses that cause MERS, SARS, Ebola, the common cold, the flu, and smallpox.

What does the presence of Delta-plus mean for beating COVID-19?

There's still a lot to learn about this particular mutation. According to Inci Yildirim, MD, PhD, a Yale Medicine pediatric infectious disease specialist and vaccinologist quoted in an article on the New Haven, Connecticut-based provider's website, we will need more data to determine the rate of spread and its impact on disease and patient outcomes.

James E. K. Hildreth, president and CEO of Meharry Medical College in Nashville, told the Washington Post that public health leaders should pay attention to other nations' experiences, pointing to Delta's devastation in India and that country's decision to label Delta-plus a variant of concern. "Again, we saw what happened with Delta in India and how quickly it spread," he told the Post. "Why would we think the Delta-plus variant would be different?"

Could it evade existing vaccines? That, of course, is the worry with any emerging mutation. And the short answer is we don't really know.

"It could be that Delta-plus turns out to be better at transmitting, better at floating around in the air, better at making more copies of itself, better at binding to cells and infecting in the first place," says Portland State's Stedman. "But it's also distinctly possible that it's actually worse."

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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