Started a decorating job on an empty property just before Christmas. When I entered the house it was like an oven, all rads turned up full. Obviously not good conditions for wallpapering but it was a rather cold day. So I turned all rads off upstairs, leaving the downstairs ones on to keep some semblance of warmth in there. That first evening, I began to develop a sore throat. The day after, a bit of a dry chesty cough. The day after that, the odd sneeze. The sore throat has gone, the chesty cough less troublesome but I now have the runny nose to accompany the sneezing. Obviously plumbers, plasterers and joiners had been in before me and maybe one of them left a 'bug' behind which thrived in the heat and just lay in wait for it's next victim.