Should runners wear a face mask outdoors?

Q: Should runners wear a face mask outdoors?

A: It depends. You won't always need a face covering while jogging or riding a bike if you're exercising with no one around, but it's good to carry one just in case.

The U.S. Centers for Disease Control and Prevention recommends people wear cloth face coverings when out in public, especially in places where it's hard to stay at least 6 feet away from others.

If it's difficult to breathe through a mask when running or doing other strenuous physical activity, find uncrowded trails or times to exercise when you won't encounter others, says Mark Cameron, an infectious disease expert at Case Western Reserve University.

The more distance you can keep between yourself and others, the better, says Summer Johnson McGee, dean of the University of New Haven's School of Health Sciences.

Masks are designed to prevent the wearer from possibly spreading the virus to others or being exposed themselves.

Q: When could a COVID-19 vaccine be ready?

A: Top health officials say the end of this year would be a best case scenario. But scientists have never created a vaccine so quickly, and there's no guarantee any under development will ultimately work.

Worldwide, testing recently started or is about to start for about a dozen potential vaccines. The most promising vaccine candidates are expected to move into larger tests this summer.

How quickly those studies can determine whether the vaccines are safe and effective depends in part on how widely the coronavirus is still spreading. The studies will need to enroll 20,000 people or more for each vaccine candidate, with half of them getting the real vaccine and the rest getting a dummy shot. Then it's a matter of waiting to see how many in each group become infected with the virus.

Answers will come faster if volunteers are recruited in places where outbreaks are worsening, a trend that can be hard to predict.

One way to speed up distribution is to start manufacturing doses before test results are in. But it's a gamble that could mean throwing away tons of vaccines that fail.

• The AP is answering your questions about the coronavirus in this series. Submit them at: FactCheck@AP.org.