Hopefully people won't throw their masks away just yet. From the article:
However, Ashish Jha, director of the Harvard Global Health Institute, expressed some skepticism of the WHO’s claim and said he thinks asymptomatic transmission is, in fact, an important source of spread and that some modeling shows as much as 40 to 60 percent of transmission is from people without symptoms.
Jha said it’s possible the WHO is making a distinction between asymptomatic spread and presymptomatic spread, when someone eventually develops symptoms but spreads the virus before they do.