A variant detected in California is now linked to more than 50% of COVID-19 cases in 44 counties in the state.

A new study warns that the pathogen is the first homegrown “variant of concern,” according to The Washington Post, because it appears to be more transmissible. A mutation on the variant makes it easier to bind to human receptor cells. Some experts worry that the variant may not only be more contagious, but also more lethal.

“The devil is already here,” said study author Dr. Charles Chiu, an infectious disease physician at the University of California at San Francisco, according to the Los Angeles Times. “I wish it were different.  But the science is the science.”

The variant consists of two different mutations called B.1.427 and B.1.429. It was first found in California in July and has been seen elsewhere in the U.S., and globally in Australia, Denmark, Mexico, and Taiwan.

The study authors note that the coronavirus will continue to mutate, which is the natural evolution of the pathogen, and people will have to continue take precautions such as masking, social distancing, and avoid large gatherings, according to the Post.

“Simply having a more infectious variant circulating is not going to be the end of the world,” said Chiu. “Fundamentally, it doesn’t change the direction we’re going, which is we want to hold cases down to where we can get the pandemic under control.”