Epidemiology: Everything Turns on One Number Crossing One
If each case produces more than one further case, an outbreak grows; below one, it fades. That threshold is simple — and almost everything else about the subject is context-dependent.
Topic
Nutrition Science
Longevity and Health: The Big Effects Are the Ones Nobody Sells
The interventions with the largest effects have been known for decades and are unglamorous. Attention flows almost inversely to effect size, for a simple reason — the big ones cannot be sold.