Was There Evidence of Asymptomatic Transmission of Coronavirus Before Last Week?

On Brian Lehrer’s radio show Friday, New York City Mayor Bill de Blasio was asked a simple question: “Didn’t we know weeks and months ago that asymptomatic people can spread this disease?”

The mayor answered in the negative. “There was suspicion, but there was not evidence.”

De Blasio also claimed that “Only in the last really 48 hours or so [has the New York City Health Department] fe[lt] they’ve seen evidence around the world, particularly a new study coming out of Singapore, that shows more evidence that this disease can be spread by asymptomatic people.”

De Blasio’s comments came a day after he encouraged New Yorkers to wear face coverings, and he cited the same study in making his recommendation. “The reason for this guidance is because the studies are showing that some asymptomatic people, some presymptomatic people appear to actually be transmitting this disease,” said de Blasio. “We don’t have perfect evidence. It doesn’t conform with what the initial information showed us weeks ago, but it does seem to be more and more evident.”