infectious disease is the deadliest enemy faced by all of humankind. True, infection is far from the only type of illness that affects each of us, but it is the only type that affects us collectively, and sometimes on a mass scale. Heart disease, cancer, even Alzheimer’s, can have devastating individual effects, and research leading to cures is laudable. But these diseases don’t really have the potential to alter the day-to-day functioning of society, halt travel, trade, and industry, or foster political instability.
