COVID-19 Mu and R.1 Variants: What You Need to Know

Like Delta and other strains of COVID-19, our tests can detect these so you can make plans to feel better.

Diagnostics Testing|Sep.27, 2021

The more COVID-19 changes, the more the lessons of the pandemic stay the same.

As the Delta variant became dominant in the U.S. — and now as Mu and R.1 establish footholds around the world — the same measures that protected us against one protect us against another.

So, with people continuing to gather at more public places and events at near full capacity — including schools — here's what you need know about the Mu and R.1 variants and how testing can help bring peace of mind, just as it has since the pandemic began.

Fundamentals: The Centers for Disease Control and Prevention (CDC) reports that at its peak, Mu made up less than 5% of all variants circulating in the United States, but it has fallen to less than 1% of all COVID-19 cases in the country, even as cases in the country have approached — and, in some places, eclipsed — daily totals from the heights of the pandemic last year.

While R.1, like Mu, is not a rival to Delta, an outbreak took place in Kentucky in September.

  • Since the end of last year, Mu and R.1 follow Delta (B.1.617.2), Gamma (P.1), Beta (B.1.351) and Alpha (B.1.1.7).

  • While Delta is believed to be the most transmissible strain of COVID-19 so far, Mu "appears more transmissible than the other variants with the exception of Delta," according to Gavin Cloherty, head of Infectious Disease Research for Abbott's diagnostics business.

  • The CDC notes that R.1 "mutations of importance" and "demonstrates evidence of increasing virus transmissibility," according to Prevention.

  • In August, the World Health Organization classified the Mu (B.1.621) variant as a Variant of Interest (VOI). Neither Mu nor R.1 have been designated as a VOI for the U.S. by the CDC at this time.

Still good advice: The virus has evolved, but general guidance for staying safe has not.

  • Now that vaccines are widely available in the U.S., the CDC recommends those who are eligible should get vaccinated as soon as possible. And with flu season approaching in the Northern Hemisphere, the CDC recommends getting your flu shot as well.

  • The CDC says you can have both COVID and flu shots.

  • Wear a mask that covers your nose and mouth.

  • Wash your hands often.

Protecting yourself: Breakthrough COVID infections after being vaccinated are exceedingly rare — less than 1% — according to the Kaiser Family Foundation. Vaccines "help protect people who are vaccinated from getting COVID-19 or getting severely ill from COVID-19," according to the (CDC).

  • The best way to know for sure whether you have COVID or the flu or something else is through testing.

  • Our tests detect Mu and R.1 as well as Delta and other COVID strains. "Our tests work," Cloherty said.

  • You can test yourself with the BinaxNOW rapid COVID antigen test.

  • Our work with partners continues. "Our Abbott Pandemic Defense Coalition is monitoring COVID around the globe to identify and analyze whether any strains on their continent are evolving," said Mary Rodgers, principal scientist and member of the Abbott Pandemic Defense Coalition.

Next steps: It's within your power to keep you and your family safe from COVID, whatever new strain comes. And they will keep coming. Along with vaccines, testing is a key component of any plan.

  • More information on COVID testing options is available here.

  • Find BinaxNOW Self Tests near you.

This story was originally published on September 27, 2021 and updated on June 03, 2022.


The BinaxNOW™ COVID-19 Antigen Self Test has not been FDA cleared or approved. It has been authorized by the FDA under an emergency use authorization. It has been authorized only for the detection of proteins from SARS-CoV-2, not for any other viruses or pathogens, and is only authorized for the duration of the declaration that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Federal Food, Drug and Cosmetic Act, 21 U.S.C. § 360bbb-3(b)(1), unless the declaration is terminated or authorization is revoked sooner. For serial testing, the BinaxNOW COVID-19 Antigen Self Test should be performed twice over 3 days, at least 24 hours (and no more than 48 hours) apart. For symptomatic use, a single test can be used.