can i ask - how do they know how the virus is being spread? ie. household

[JamminDoughnuts]

and is not spread via pubs and restaurants,
is spread through shopping

how do they know?

high spread in households i understand but people picked up the virus somehwere?

Is that not what test and trace tries to pinpoint?. Cant be pubs and restaurants in the Central belt of Scotland just now as they're all closed but cases are still high!