While scientists are keeping a watchful eye on the British and South African variants of the coronavirus, a new study found seven homegrown variants with the same troubling mutation.

According to The New York Times, a team of researchers traced seven variants of SARS-CoV-2, the virus that causes COVID-19, across several states in the U.S. Their findings, published Sunday, have not been peer reviewed. However, the study highlighted the evolution of different lineages of the virus which could affect its transmission, said the authors. All seven variants have a mutation in the same genetic location.

“There’s clearly something going on with this mutation,” said co-author Dr. Jeremy Kamil, Ph.D., associate professor of microbiology and immunology at Louisiana State University. The scientists say that the suspicious mutation is located in an area where the virus invades human cells, so this discovery could become problematic for the controlling the pandemic.

While viruses are known to genetically evolve, scientists do not know what consequences these mutations will have. Besides being potentially more contagious, they may reinfect those who have already had COVID-19.

According to NPR, people who believe they have earned immunity from the first infection, may be susceptible to a second illness caused by a new variant.

“We know that you can become re-infected even with the same version of the virus,” said Ravinda Gupta, of the Cambridge Institute of Therapeutic Immunology and Infectious Disease. “The mutations could put even more of a dent in the barrier of resistance.”