What are 4 characteristics of epidemic diseases that cause them to die out and not reappear for a long period of time?This can be found in Chapter 11
The characteristics of an epidemic disease are:
- the speed with which they spread
- how long it takes to recover or die
- whether the disease grants immunity
- and whether the disease has human hosts
Jared Diamond's Guns, Germs, and Steel: The Fates of Human Societies discusses how the world was influenced by a variety of factors, including firearms, disease, and industry.
In Chapter Four, Diamond says:
The infectious diseases that visit us as epidemics, rather than as a steady trickle of cases, share several characteristics. First, they spread quickly and efficiently from an infected person to nearby healthy people, with the result that the whole population gets exposed within a short time. Second, they're “acute” illnesses: within a short time, you either die or recover completely. Third, the fortunate ones of us who do recover develop anti-bodies that leave us immune against a recurrence of the disease for a long time, possibly for the rest of our life. Finally, these diseases tend to be restricted to humans; the microbes causing them tend not to live in the soil or in other animals. All four of these traits apply to what Americans think of as the familiar acute epidemic diseases of childhood, including measles, rubella, mumps, pertussis, and smallpox.
He goes on to explain that when microbes spread rapidly and the disease takes hold quickly—and ends quickly—there is no part of the population left who is still infected. People are either dead or immune. The immunity of the survivors ensures that the disease dies out at least until new children are born who can act as hosts or until new people join the population.
Diamond gives the example of measles in the Faeroes, a group of islands in the Atlantic. When measles infected the population in 1781, it quickly died out. It was gone for more than 50 years until a ship from Denmark came bearing a carpenter who was infected with measles. Three months later, the Faeroe population of 7,782 had developed measles and run the course of the disease. Diamond then explains that measles is likely to die out in populations that consist of fewer than 500,000 people.
Here are the four important characteristics of these kinds of diseases:
- They spread rapidly and efficiently from person to person. This means that everyone in a given area gets the disease all at once.
- They are "acute" illnesses where you only have them for a short time. You either die quickly or recover. This means that a lot of the people who could get the disease die. Then the disease has fewer people to infect.
- The rest of the people (the ones who don't die) become immune. This means the disease can't spring up again in the same population.
- The diseases have to have human hosts -- they can't live in the soil, for example.
So all of this means that the disease sweeps through and kills a bunch of people but then it can't stay there any longer because there are no potential hosts. It goes away and can't return until there's a new generation living in the place.