The Centers for Disease Control and Prevention issued a new mandate on Tuesday requiring anyone traveling on public transportation to wear a mask.

With almost 500 cases of the more contagious UK strain found in the U.S., UTRGV Chief Medical Officer Dr. Michael Dobbs says some masks aren’t as effective as others.

“With that new variant of COVID, the early thinking is that maybe some of the masks aren't as effective as they had hoped - some of the homemade ones,” said UTRGV Chief Medical Officer Dr. Michael Dobbs.

The CDC recommends choosing masks that have two or more layers of washable fabric, completely cover your nose and mouth, and fit snugly against the sides of your face and don’t have gaps.

The CDC also launched a new guide on its website showing how to wear a mask, how to take off a mask, how to clean a mask, special considerations to take and other resources.