This is a timely question since April marks the 50th anniversary of the Salk injectable, killed-poliovirus vaccine and the beginning of the end of the polio epidemics. Actually, no one knows where the poliovirus came from. Animals are not carriers of the poliovirus since it occurs naturally only in humans. However, it's fortunate for us that other species can catch polio from people. Back in 1908 researchers injected fluid from a boy who had died from polio into monkeys, who became paralyzed. Those sick monkeys then were able to paralyze healthy monkeys, proving that polio was caused by an infectious agent. What's more, a vaccine would never have been possible without monkeys' susceptibility to polio. By studying polio-infected monkeys, neuropathologist David Bodian was able to discover that there are three different types of poliovirus. He also discovered the path the poliovirus followed--from the intestines into the blood and then into the brain and spinal cord--findings that indicated a vaccine that stimulated the creation of blood-born antibodies would protect against polio.

Once Bodian laid this groundwork he, Jonas Salk and Albert Sabin used more monkeys to see if potential vaccines generated antibodies to all three types of poliovirus. Sabin stated that "approximately 9,000 monkeys" had been used to test his oral, live/attenuated polio vaccine. Fortunately, the primate world got something back for its sacrifice on behalf of humankind. In 1966 an outbreak of polio in a Tanzanian village spread to a chimpanzee colony being studied by Jane Goodall. Although 12 chimps died or were paralyzed before the colony could be vaccinated, the polio vaccine saved the rest of the chimps.

Sadly, the colony's reaction to one affected chimp is reminiscent of the experience of many human polio survivors. An older male named McGregor was paralyzed from the waist down and dragged himself around the camp using his arms. Jane Goodall writes in In the Shadow of Man: "One of the most tragic things about the whole tragic affair was the reaction of the chimps to the stricken paralyzed male." McGregor was menaced by the male chimps and was beaten by one of them. Others kept well away from him. Goodall watched a group of chimps grooming each other in a tree, grooming being the primary means of chimp socialization. She writes that McGregor "dragged himself from his nest ... and in short stages began the long journey to join the others. When at last he reached the tree ... he pulled himself up until he was close to two grooming males. With a loud grunt of pleasure he reached a hand toward them in greeting. But even before he made contact they both had swung quickly away and without a backward glance started grooming on the far side of the tree. For a full two minutes old McGregor sat motionless, staring after them. And then he laboriously lowered himself to the ground. As I watched him sitting there alone ... and when I looked up at the groomers in the tree I came nearer to hating a chimpanzee than I have ever been before or since."

McGregor's rejection mirrors the painful experiences of human polio survivors that make them too frightened of rejection even today to "look disabled" by changing their lifestyles in order to manage PPS. These experiences also make clear why vaccination must continue, in the United States and throughout the world, so that polio will be eradicated.

Unfortunately, 50 years after the development of the vaccine, the same mistake is being made today that was made when the polio vaccine was released in 1955. All of the world's attention and resources are being directed toward vaccination while too few of the world's 20 million polio survivors and their health care providers know about post-polio sequelae. This need not be so! There are sufficient resources to not only eradicate polio, but also to educate about and treat PPS.