LONDON — So this is what it has come to: a television personality and three former athletes in high dudgeon interrogating a learned medical doctor on the BBC in a segment of car crash-style TV that encapsulates so much of what passes in 2017 for dialogue in the public arena. On the one hand, rational, even scientific, thought begging to be heard. On the other, know-it-all counterpoint rooted in grievance and conflict.

The flashpoint at these 2017 IAAF world championships: an apparent outbreak of norovirus. Public Health England issued a statement late Thursday saying it had “been made aware of approximately 40 people reporting illness,” three confirmed by lab testing as norovirus.