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"We Have Had It." The second great paradox of polio follows naturally from the first: as a disabling disease, it is a product of civilized man's passion for sanitation, sewerage and other public-health measures. While other infectious diseases have decreased with higher living standards, paralytic polio has been increasing. Man himself is the only known natural reservoir of the virus. How it reaches him and enters his system is not known for certain, but the current consensus is: person to person, rather than by pests (though flies can carry the virus), and through the mouth. It may be hand to mouth, or by inhalation, or both.
For a few days the virus courses through the bloodstream—one of the most vital recent discoveries, made simultaneously by Baltimore's Dr. David Bodian and Yale's Dr. Dorothy Horstmann. While there, it stimulates the human system to develop antibodies that will give some degree of immunity -against future infection by virus of the same type but not to any appreciable degree against virus of the two other known types.
The virus multiplies somewhere along the digestive tract and is excreted from the intestines. In unsanitary societies, everybody is soon exposed to the virus. If the challenge of infection comes in earliest infancy, that is good. For if the mother has been exposed and has antibodies, she passes them on to her baby. They stay in the baby's bloodstream, giving "passive immunity" (TIME, Nov. 5, 1951) for about three months. Exposure to the virus during that time usually causes no detectable symptoms, but results in lifelong, active immunity.
As man has lifted himself slowly out of his own filth, he has reduced the likelihood that a child will be exposed to a virus that is mostly flushed down the drain. And the later the age of exposure, the greater is the danger that the infection will develop into a grave, feverish and perhaps paralytic illness. The reason why most of the populace seems to be immune, says Dr. Paul, is simply: "We have had it." But without knowing it. As U.S. standards of hygiene have gone up, so has the age range in which paralytic polio strikes. Nowadays. 22% of victims are adults. Strangely, the disease attacks more boys than girls under 20, but more women than men over 20.
The Great Breakthrough. Five years ago came the great breakthrough in the campaign to conquer polio. There had already been ill-starred attempts to make a vaccine, but in everything that they tried to do the researchers were hampered by one stubborn fact: most kinds of polio virus, it seemed, could be grown only in nerve tissues of living men or monkeys. And a vaccine prepared from such material would hold the frightful danger of causing an allergic inflammation of the brain, a malady even worse than the one it was designed to prevent.
A team of Harvard researchers headed by the brilliant virologist, John F. Enders, reported in Science in January 1949 that they had succeeded in growing polio viruses in tissue cultures of non-nervous tissues. From the obscure technical lan guage they used, only another virologist could have divined the explosive import of their work. In fact, Enders' discovery was to a polio vaccine (and to much other health-saving virus research) what Einstein's cryptic E = mc2 was to the atom bomb.