The health of one's immune system seems to be a key factor in the severity of the disease. A great measure of this is Vitamin D levels. There seems to be a direct correlation between vitamin D deficiency and the death rate.

UV-B rays from the sun turn cholesterol in the skin into Vitamin D. It turns out that High Fructose Corn Syrup destroys Vitamin D (HFCS has some free molecules that causes the vitamin to break down).

Immune system health is the way to prevent the disease.