Viral

– You appear to be under the weather.
– Yes. I seem to have picked something up. A cold.
– You had a cold a couple of weeks ago. Has it lasted all this time?
– No. This is a new one. Although superficially it looks similar and has basically the same symptoms, I am confident that deep down it is uniquely different from the last cold.
–  Well, that's something to be thankful for: a bit of variety. I suppose it's comforting to know that your respiratory system represents a hospitable environment for any passing bug in search of shelter. Altruistic of you, in a way.
– I like to do what I can to help.
– You don't suppose it's catching, do you?
– Well, I guess I must have caught it at some stage. These things don't just appear from nowhere. Unless they evolve quietly from something else. Perhaps from some spare cell of mine that wasn't doing anything useful.
– Only I'm not particularly keen to go down with some unpleasant infection.
– It's not all that unpleasant. Though spending a whole day sneezing isn't much fun. Not to mention the listlessness. And lack of sleep. Now that I come to think about it, I suppose it is fairly unpleasant.
– Perhaps you should be quarantined. Put into isolation. Just to be on the safe side. And for the benefit of the rest of humanity.
– How long for?
– As long as it takes. I could come and visit you occasionally. Or, at least, wave at you through the window.