WASHINGTON (CBS/AP) — The head of the Centers for Disease Control and Prevention says Massachusetts and other states shouldn’t be relaxing coronavirus restrictions just yet.

Dr. Rochelle Walensky told reporters Friday the CDC is looking at data that COVID-19 cases have been increasing the past three days, but more time is needed to see if that is a blip or the start of a trend.

READ MORE: Boston Police Cruiser, Sedan Collide In Early Morning Crash In Roxbury

Walensky, the former chief of infectious diseases at Massachusetts General Hospital, said virus mutations spreading in the U.S. are among the CDC’s biggest concerns. Along with a more transmissible strain first detected in Britain, scientists here are tracking variants in New York and California, which also appear to spread more easily.

“We may be done with the virus, but clearly the virus is not done with us,” says Walensky, stressing now is not the time to relax protective measures like wearing masks and avoiding gatherings.

Governor Charlie Baker announced Thursday that Massachusetts will ease restrictions starting Monday. Walensky was asked about that Friday.

READ MORE: Recent Lawrence High School Fights Prompt City Officials To Convene For Emergency Meeting

“Given the trends that we’ve seen in just the last couple of days, I would say we can’t be in a place where we’re lifting restrictions right now,” she said. “The CDC would really encourage people and states not to expand and release restrictions.”

Cases and hospitalizations have fallen dramatically in Massachusetts and much of the nation since the January peak that followed the winter holidays. Deaths have also declined. But Walensky says those gains could be in jeopardy because the background level of cases is still too high.

“We have to carefully look at what happens over the next week or so with those numbers before you start making the understandable need to relax on certain restrictions,” said Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases.

MORE NEWS: 24-Year-Old Sets New American Record During Women's 10K Race In Boston

(© Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)