The Tipping Point: How Little Things Can - By Gladwell, Malcolm Page 0,7
But they also sometimes tip when something happens to transform the epidemic agent itself.
This is a well known principle in virology. The strains of flu that circulate at the beginning of each winter’s flu epidemic are quite different from the strains of flu that circulate at the end. The most famous flu epidemic of all—the pandemic of 1918—was first spotted in the spring of that year and was, relatively speaking, quite tame. But over the summer the virus underwent some strange transformation and over the next six months ended up killing between 20 and 40 million people worldwide. Nothing had changed in the way in which the virus was being spread. But the virus had suddenly become much more deadly.
The Dutch AIDS researcher Jaap Goudsmit argues that this same kind of dramatic transformation happened with HIV. Goudsmit’s work focuses on what is known as Pneumocystis carinii pneumonia, or PCP. All of us carry the bacterium in our bodies, probably since birth or immediately thereafter. In most of us it is harmless. Our immune systems keep it in check easily. But if something, such as HIV, wipes out our immune system, it becomes so uncontrollable that it can cause a deadly form of pneumonia. PCP is so common among AIDS patients, in fact, that it has come to be seen as an almost certain indication of the presence of the virus. What Goudsmit did was go back in the medical literature and look for cases of PCP, and what he found is quite chilling. Just after World War II, beginning in the Baltic port city of Danzig and spreading through central Europe, there was an epidemic of PCP that claimed the lives of thousands of small children.
Goudsmit has analyzed one of the towns hit hardest by the PCP epidemic, the mining town of Heerlen in the Dutch province of Limburg. Heerlen had a training hospital for midwives called the Kweekschool voor Vroedvrouwen, a single unit of which—the so called Swedish barrack—was used in the 1950s as a special ward for underweight or premature infants. Between June 1955 and July 1958, 81 infants in the Swedish barrack came down with PCP and 24 died. Goudsmit thinks that this was an early HIV epidemic, and that somehow the virus got into the hospital, and was spread from child to child by the then, apparently common, practice of using the same needles over and over again for blood transfusions or injections of antibiotics. He writes:
Most likely at least one adult—probably a coal miner from Poland, Czechoslovakia, or Italy—brought the virus to Limburg. This one adult could have died from AIDS with little notice....He could have transmitted the virus to his wife and offspring. His infected wife (or girlfriend) could have given birth in a Swedish barrack to a child who was HIV infected but seemingly healthy. Unsterilized needles and syringes could have spread the virus from child to child.
The truly strange thing about this story, of course, is that not all of the children died. Only a third did. The others did what today would seem almost impossible. They defeated HIV, purged it from their bodies, and went on to live healthy lives. In other words, the strains of HIV that were circulating back in the 1950s were a lot different from the strains of HIV that circulate today. They were every bit as contagious. But they were weak enough that most people—even small children—were able to fight them off and survive them. The HIV epidemic tipped in the early 1980s, in short, not just because of the enormous changes in sexual behavior in the gay communities that made it possible for the virus to spread rapidly. It also tipped because HIV itself changed. For one reason or another, the virus became a lot deadlier. Once it infected you, you stayed infected. It stuck.
This idea of the importance of stickiness in tipping has enormous implications for the way we regard social epidemics as well. We tend to spend a lot of time thinking about how to make messages more contagious—how to reach as many people as possible with our products or ideas. But the hard part of communication is often figuring out how to make sure a message doesn’t go in one ear and out the other. Stickiness means that a message makes an impact. You can’t get it out of your head. It sticks in your memory. When Winston filter tip cigarettes were introduced in the spring of 1954, for example, the company