Ted listens, smiling a little at the thought of Sherlock being sick and insisting on working. Sounds like him. Clearly he valued the investigation higher than a) not infecting other people, and b) taking the time to recuperate so he could get well faster. But Ted would definitely insist on wrapping him up with a blanket and feeding him soup or something. He's glad Joan insisted about the tea.

At the last bit he looks playfully affronted. "So he does drink it for that!" he exclaims, amused. "What did you mean he didn't drink it for, his blood pressure?" he asks, grinning.