The coronavirus questions that scientists are racing to answer

The outbreak of a novel coronavirus in China and its spread to more than a dozen countries has presented health experts with a rapidly evolving and complex challenge.

That means there are a lot of unknowns.

Here are some of the outstanding questions that doctors, scientists, and health agencies are rushing to answer. (And a reminder that, already, they’ve learned quite a lot.)

When are people contagious?

One of the luckiest breaks the world got with the SARS outbreak of 2002-2003 was that people weren’t contagious until they developed symptoms. The same is true of MERS. As a result, it became easier for health officials to try to limit spread once they identified a new case.

Public health experts watching this outbreak unfold have been hoping 2019-nCoV, which is a member of the same virus family, would