As the number of novel coronavirus cases continues to rise nationwide, the recurring message from many public health experts and doctors has been simple: Wearing masks saves lives.

“We are not defenseless against covid-19,” Robert R. Redfield, director of the Centers for Disease Control and Prevention, said in July. “Cloth face coverings are one of the most powerful weapons we have to slow and stop the spread of the virus – particularly when used universally within a community setting.”

But as face coverings have become increasingly commonplace in American life, so have questions about efficacy — and now a group of researchers from Duke University are aiming to provide some answers.

A lifeguard wearing a gaiter-style face covering surveys the water at Hampton Beach in Hampton, N.H., on Aug. 5. (Joseph Prezioso/AFP/Getty Images)
In a recently published study, the researchers unveiled a simple method to evaluate the effectiveness of various types of masks, analyzing more than a dozen different facial coverings ranging from hospital-grade N95 respirators to bandanas. Of the 14 masks and other coverings tested, the study found that some easily accessible cotton cloth masks are about as effective as standard surgical masks, while popular alternatives such as neck gaiters made of thin, stretchy material may be worse than not wearing a mask at all.