A dank November night, and you're just finishing the first bottle of red when the final guest arrives.
"Don't come too close – I've got a cold."
Thinks: I wouldn't come within 100 miles. But what has actually happened, see, is that you have come to me. I am far too polite to get up and leave, so I will sit opposite you and pretend that the pleasure of your company makes up for the week I am now condemned to spend gagging on my own snot. Most galling is the fact that you are no fun at all right now. You exude misery and mucus in equal measure. Why? Because you've got a cold.
Says: "There's a nasty one going around at the moment. Poor you."
Or, you're in the office, and the tell-tale waft of menthol signals it wasn't a heavy night that's left Teresa from accounts looking as if she's been coughed up by a whale.
Soon there will be the heaped tissue balls, each concealing a nugget of virus-laden sputum, like the devil's Ferrero Rocher. Then, one by one, your colleagues fall. The catch of phlegm in throat, the sniff-swallow-sniff, the skin that peels back from overworked nostrils, until your desk is besieged by a troupe of proto-zombies weakly debating the merits of Night Nurse versus Lemsip Max.
Can you work from home, simply because everyone in your department is ill? Can you switch train seats to avoid the sneezing child? Can you refuse to kiss your own mother? Of course not. That is unacceptable behaviour.