What Was the R.1 COVID-19 Variant?

Data suggested the variant had been in the US since April 2021, when it was discovered after an outbreak in a Kentucky nursing home.

In July 2021, the World Health Organization announced that the Delta variant had surpassed other mutations of SARS-CoV-2 as the most prominent strain in the world and that it was a "variant of concern." Researchers then identified another strain, the R.1 variant, that was responsible for a small number of COVID-19 cases in the United States and worldwide.

What Is the R.1 COVID Variant? Here's What We Know So Far , Corona virus digitally generated image on white background

The R.1 variant of SARS-CoV-2, the virus that causes COVID-19, was first detected in Japan in 2020; it then made its way to other countries, including the US. In fact, a Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention (CDC), dated April 21, 2021, suggested the mutation had been present in the United States as early as April 2021, and that it had been in part responsible for an outbreak among nursing home patients in Kentucky earlier that year.

When the Kentucky Department of Health and a local health department investigated a COVID-19 outbreak of vaccinated patients in a skilled nursing facility, they found the R.1 variant during genome sequencing—suggesting this mutation may be more likely to cause breakthrough infections than previous strains.

Here's what you need to know about the R.1 COVID-19 variant, according to infectious disease experts.

What Was the R.1 Variant?

According to Amesh A. Adalja, MD, a senior scholar at Johns Hopkins Bloomberg School of Public Health's Center for Health Security, the R.1 variant was a version of the SARS-CoV-2 virus that had mutations associated with changes in the function of the virus. In other words, as with any new strain, R.1 could have affected people differently than the original version of the virus.

That said, identification of this new strain wasn't necessarily cause for panic. While any new variant can pose a threat, Dr. Adalja said it was unlikely the R.1 variant would overtake the Delta variant as the most severe or transmissible mutation of the SARS-Cov-2 virus.

"I don't suspect it will be a major problem because it doesn't have the ability to displace Delta," said Dr. Adalja. "It's really hard for these types of mutations to get any foothold in a country that has the Delta variant present."

While Dr. Adalja didn't necessarily expect any different symptoms from this strain, he said it could potentially affect more people who are vaccinated against COVID-19. "The issue is this mutation does have mutations we saw with the B and G variants people forgot about," said Dr. Adalja. "That may make breakthrough infections more common, but it's not about that." How rampant a strain becomes, Dr. Adalja emphasized, has more to do with its transmissibility—so it was pretty unlikely this one would displace the Delta variant.

As of September 2021, the R.1 variant only accounted for 0.5% of COVID-19 cases in the US and worldwide; according to Ramon Lorenzo Redondo, PhD, research assistant professor of infectious diseases at Northwestern University Feinberg School of Medicine, the R.1 mutation hadn't been sequenced—or genetically identified—in a US case since early August 2021. "This version of the virus never accounted for more than 1% of worldwide cases, even at its peak," Redondo said.

What's the Best Way To Stay Safe From the R.1 Variant?

All the same safety measures that applied before still apply when a new strain is identified. "There will be many new variants just like this one," Dr. Adalja said. "What's important to remember about all these is that it's hard for them to do anything on a grand scale when the country is already so bathed in the most fit version of the virus."

According to Redondo, the best way to keep yourself safe from Delta, R.1, or any strain of SARS-Cov-2, is to get fully vaccinated and continue practicing CDC-recommended precautions, such as masking in public. Protecting yourself from getting infected is also the most effective method for stopping the virus from continually mutating.

"The only way to stop new variants is to stop the number of infections," Redondo said. "If you drive the population to very low numbers and the diversity is constricted, the virus can't evolve as much."

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 CDC, WHO, and their local public health department as resources.

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