Re: “Speaking as a dad and a doctor, we should rethink coronavirus school closures” [March 24, Opinion]:

In a lecture I attended on COVID-19 by a Swiss professor of infectious diseases, I was told that people with COVID-19 are contagious a few days before they have symptoms.

If so, how can the system the author is under as a doctor — and the system he proposes for student-teacher meetings — be effective in preventing transmission?

Phoebe C. Warren, Seattle