A coronavirus testing station in Seoul, South Korea on August 26, 2020.
  • The Delta Plus variant is the Delta variant with an extra mutation. It has reached nearly 30 countries.
  • It's not yet clear whether Delta Plus is more transmissible than Delta.
  • The fact that Delta remains dominant worldwide is a sign that Delta Plus won't overtake it soon.
  • For more stories visit Business Insider.

As the Delta variant tears across the globe, scientists are keeping a close eye on its relative: Delta Plus.

The two variants are genetically similar, which is why they share the same Greek letter. But Delta Plus (also known as AY.1) has an extra mutation in the code for its spike protein, which helps the coronavirus gain entry to our cells.

India's health ministry said last month that Delta Plus appears to spread more easily than Delta, and can potentially bind more easily to lung cells or resist antibody drugs. But an Indian genomics consortium suggested more recently that Delta's sub-lineages probably aren't more transmissible than Delta itself. As of July 23, India had recorded no more than 70 Delta Plus cases.

Both the US Centers for Disease Control and Prevention and World Health Organization still track Delta Plus as part of the Delta variant, meaning the cases aren't separated. But data from Scripps Research's Outbreak.info tracker suggests that just 430 Delta Plus cases have been detected worldwide.

South Korea announced Tuesday that it had recorded its first two cases of Delta Plus. The nation is battling its heaviest surge of infections yet, most likely driven by the original Delta strain.

"It doesn't terrify me any more, really, than Delta," Andrew Read, who studies the evolution of infectious diseases at Pennsylvania State University, said of Delta Plus.

Although Delta Plus has made its way to around 29 countries and 17 US states so far, Read noted that "the widespread geographic nature doesn't mean that it's one thing spreading widely."

"It could be that it's several independent events that are spreading locally," he said.

In the US, Delta Plus cases peaked in late June, though they still represented less than 5% of the nation's sequenced cases at that time, according to Outbreak.info. Health experts say that's a sign that Delta Plus isn't outcompeting other variants.

"If it started to rise in frequency against the Delta variant, that would tell you that it was perhaps on track to take over from Delta - but we're not really seeing that at the moment," Read said. "If it had a big advantage, we'd be seeing it rising in frequency pretty rapidly."

Scientists don't know how well vaccines perform against Delta Plus

For Delta Plus to be a serious concern, scientists would need concrete evidence that it's more transmissible than Delta, causes more severe disease, or resists protection from vaccines to a greater degree.

"I could imagine that, because the mutation is in the spike [protein], it might have some advantages in terms of immune evasion and some disadvantages in terms of binding to the ACE2 receptor," Read said. That receptor serves as the port of entry for the coronavirus.

But Public Health England told Insider in June that there was no evidence that Delta Plus's extra mutation made the virus any more severe or reduced vaccine effectiveness relative to Delta.

While Delta seems to have challenged how well vaccines prevent infection and transmission, coronavirus shots still reduce the risk of getting Covid-19 eight-fold, and the risk of hospitalization or death 25-fold, according to recent data from the CDC.

A study in the New England Journal of Medicine found that Pfizer's two-dose vaccine reduces the risk of a symptomatic Delta infection by 88%. Another study that hasn't been peer reviewed found Pfizer and Moderna's mRNA vaccines reduce the risk of hospitalization by 91% for people who aren't immunocompromised.

When it comes to Delta Plus, a study from Indian researchers that's still awaiting peer review found that Covaxin - one of India's two main coronavirus vaccines - still neutralizes the variant. Covaxin is similar to China's Sinovac shot.

Get the best of our site emailed to you every weekday.

Go to the Business Insider front page for more stories.