The Minnesota Department of Health on Monday confirmed the first domestic case of a highly transmissible strain of the coronavirus, known as the P.1 variant, was discovered in a Twin Cities resident.

The strain, which is believed to be more easily transmissible between humans than the original virus, was first discovered in four travelers from Brazil early this year during a routine screening at Haneda airport outside of Tokyo, Japan.

The variant contains “a set of additional mutations that may affect its ability to be recognized by antibodies,” according to the CDC. Researchers do not yet know if the P. 1 variant causes more severe illness than other strains.

The patient in Minnesota who tested positive for the new strain had also recently traveled to Brazil, officials said in a statement Monday. The unidentified person became ill during the first week of January and reported his conditions to city health officials, and a sample was taken on Jan. 9. 

“We know that even as we work hard to defeat COVID-19, the virus continues to evolve as all viruses do,” Minnesota Commissioner of Health Jan Malcolm wrote in a statement. “That’s yet another reason why we want to limit COVID-19 transmission – the fewer people who get COVID-19, the fewer opportunities the virus has to evolve. The good news is that we can slow the spread of this variant and all COVID-19 variants by using the tried-and-true prevention methods of wearing masks, keeping social distance, staying home when sick, and getting tested when appropriate.”

Minnesota health officials also reported several new cases of the B.1.1.7 variant, yet another more contagious and possibly more deadly variant of the original coronavirus sweeping through Britain. The state’s total for the B.1.1.7 strain currently stands at eight, but officials believe there are likely more. 

While the discovery of the P. 1 variant concerned some, many experts have warned that the B.1.1.7 strain is more likely to become the dominant source of infection in the U.S. by March. It has been reported in over 20 states so far. 

The more the virus spreads, the more opportunities it has to mutate. The fear is that it will ultimately render the vaccines ineffective.

To guard against the new variants, President Joe Biden on Monday added South Africa to the list of more than two dozen countries whose residents are subject to coronavirus-related limits on entering the U.S.

Most non-U.S. citizens who have been to Brazil, Ireland, Britain and other European nations will be barred from entering the U.S. under the rules re-imposed by Biden after President Donald Trump had moved to relax them.

Fauci said scientists are already preparing to adjust COVID-19 vaccines to fight the mutated versions.

He said there is “a very slight, modest diminution” of the effectiveness of COVID-19 vaccines against those variants, but “there’s enough cushion with the vaccines that we have that we still consider them to be effective” against both.

The Associated Press contributed to this report.