When you first get a cold or flu, put on pajamas or sweats, and get a gallon of Gatorade and a gallon of water. Put both by the bed. Put every single blanket in the house on the bed, and get under 'em. Don't come out except to go to the bathroom. Stay there for 24 hours. Then, wash all the blankets, which will be a fetid tunnel of sweat and armpit stink...
The idea is, your fever helps your immune system work and keeps the viruses from reproducing as efficiently, so by holding the heat in you make a sort of artificial fever. It's always worked for me.