When we were recovering from a really sick few months last winter, I washed walls and chairs and floors with a solution of 1/2 water, 1/2 vinegar and some sweet orange essential oil. The vinegar kills stuff, removes odors and the orange lifts spirits and sweetens the air.
Then I used the Merlin's Magic recipe from Clean House, Clean Planet. Basically, a little Dr. Bronner's, a lot of distilled water and 20 drops of TTO. I used this for doorknobs and toilets and sinks and countertops.
And then we ate lots of garlic, drank lots of water and upped our Vitamin C. We also napped a lot and ate salty soup (with more garlic).
If you can, try to get out of the house a little, too. Or open a couple windows for a few minutes each day to recycle the air a bit.
Oh! And change the furnace filter, wipe down the floor and intake vents.