The causes of death from many deadly pandemic diseases are: dehydration from barfing/diarrhea, and drowning in your own phlegm. Add high fever and an immune overreaction called a "Cytokine storm" to that also. Therefore do the following before you get sick:
Do what you can to maintain a good immune system. Get enough exercise and eat healthy. Taking a multivitamin can help too.
Stock up on Pedialyte, Gatorade (or similar), and Imodium AD (the generic is Loperamide). These will help you fight dehydration.
Here is a recipe for homemade Gatorade substitute:
1/2 teaspoon salt
2 tablespoons honey or sugar
1/4 teaspoon potassium chloride (salt substitute)
1/2 teaspoon baking soda
1 quart water
Consider also making your homemade Gatorade with sulphured molasses. Sulphur has antibiotic properties.
Stock up on cough medicine that has guaifenisin in it (an expectorant, for coughing). You can get guaifenisin pills, too, as well as syrup.
Stock up on aspirin, Tylenol, Advil - get all three. If people are dying from cytokine storm overreactions, then aspirin is the best bet because it will dampen the effects of that. The reason why the swine flu killed mostly young adults the first time, was because of a cytokine storm. Their immune systems were the strongest, and overreacted the most.
Breathe steam to loosen up phlegm. If you are coughing up phlegm easily, this is a good thing. This means it's coming out. If you get pneumonia, the only way for the phlegm to come out is by coughing it up. Staying well hydrated is key here.
If whatever is going around is bacterial, and you can't get antibiotics or they're not helping, you might get some good out of colloidal silver. You can make your own by electrolyzing pure silver in distilled water (both terminals should be pure silver, like one of those new Liberty .999 pure silver dollars. Don't use old silver coins, they're only 90% silver). Colloidal silver is an old-fashioned precursor to antibiotics. Some people drink a shot every other day or so as a preventative health drink.
If whatever is going around is a virus, then antibiotics won't help you. For the flu, you might be able to get Tamiflu, or there's also a nonprescription drug called Sambucol which is made from elderberries and is good for the flu.
It's best to take to bed and get rest and plenty of fluids. Also if there's an outbreak, it might be best not to go out for a couple weeks, so you will want to have extra food in the house and clean water put up, in case the water supply is a problem. You want at least 1 gallon per person per day, but if you want to do dishes or bathe and the water's cut off, I'd get 2 gallons. And even more if you want to flush the toilet.