Well, first of all, when it's cold enough, germs can't survive. So like, if you lived in the North Pole for example, you'd never get sick, so basically, by going outside when it's 40 below, you won't get more sick, HOWEVER... Like, when you're outside in the cold, and someone says, "Put on a jacket or you'll catch a cold." well in the cases where it's too cold for germs, you can still get sick. For example, you go outside in the cold without a jacket, then the cold will cause your immune system to wear down, then when you're elsewhere, where it's warmer, where germs can survive, then you'll get sick because your immune system is shot from the cold. So while you're out there, you won't get more sick (though you'll probably feel more sick), but you can get more sick much more easily once you're back inside, especially since your immune system is already busy fighting whatever you currently have. You should get lots of rest and drink lots of fluids to get better quicker. You shouldn't go help him until you're all better, in the mean time you should rest, in bed, and like I said, drink lots of liquids. And I don't mean sodas and stuff like that either, those are worse for you because when you have a caffeine/sugar crash, your body will suffer hard and it'll take longer to get better. I've found drinking things like Gatorade help when you're sick because of its replenishing properties, it helps fuel your body to fight whatever ailment you suffer from. In general though, drink lots of water. Also, if you have a fever, taking aspirin will help push the fever down, however doing so will make you take longer to get better, so if you get a fever, let it burn.
