Can individuals infected with the Wuhan coronavirus spread it to others even if they aren’t showing symptoms?

It’s one of the most important questions confronting scientists. If even asymptomatic people can spread the virus, then it will be much, much harder to slow its spread.

Doctors in China claimed asymptomatic transmission was possible, and a letter published Jan. 30 in the New England Journal of Medicine appeared to back them up.

In the letter, scientists described a cluster of infections in Germany that had started with a traveler from Shanghai. The traveler had seemed healthy during her four-day visit to Bavaria, the researchers reported, and started feeling ill only after she boarded a return flight to China.