Wendy Zuckerman

And then they ask the people, in the last four weeks, have you had symptoms like coughing, shortness of breath?

And here's what Vivek's team found.

63 people in his study had antibodies to this virus.

And how many had no symptoms?

Oh, wow.

So in Vivek's study, 25 people, or around 40% of those with antibodies, said they didn't have symptoms.

But don't hang your hat on that 40% because Vivek's study was small and it's preliminary.

Plus, another early study out of France found a totally different number that less than 20% of the people who had antibodies said they never had symptoms.

So why are these numbers so different?

Well, we're just so early in this.

We basically haven't studied enough people with these antibody tests to get a handle on how many people are truly asymptomatic.

Vivek says that eventually these antibody tests might help us get to the bottom of this asymptomatic question.

But for now...

we need to look elsewhere.

We need to go on an adventure back to that Diamond Princess cruise ship, the ship that Mark was on.

Because this cruise ship gives us some of the best information about asymptomatic people.

Yes, I tell you, there hasn't been a ship this important to science since the HMS Beagle.

While passengers were going through quite the ordeal on this ship, scientists were all watching this from afar.

This is Mateusz Plankinski.

He's an epidemiologist with the CDC, and he was deployed as part of the CDC's cruise ship response team.