We should soon understand this better. What the virologist was saying was informed opinion. But…
…there's little evidence that children are infectious. The S Australia paper found little evidence of transmission via children.
The Charité hospital found children were as likely as adults to be infected, and had similar viral loads, but remained relatively well.
The Charité paper concluded that children might be as infectious as adults.
Certainly, with flu, they are. They produce copious quantities of virus - more, and for longer than adults. But Covid-19 is not flu…
Covid-19 is predominantly spread by coughing.
Flu is spread also via snot, sneezing.
If children have no or minimal symptoms with Covid-19 (cf flu) , perhaps they don't cough as much,and are less infectious.
That could reconcile the findings of the two studies. The virus is there, in childrens' nasopharynges; but because they have few symptoms they cough and sneeze less, and are, therefore, less infectious.
Let's hope real world studies are teasing these issues out.
Ps links to both of the papers I mentioned are in peterenglish.blogspot.com/2020/04/more-q…