The Hungarian physician Ignaz Philipp Semmelweiss (1818–65) insisted that childbed fever which killed so many mothers in childbirth, was spread by the doctors themselves, since they went from autopsies straight to women in labor. He fought to get the doctors to wash their hands before attending the women, and when he managed to enforce this, in 1847, the incidence of childbed fever dropped precipitously. The insulted doctors, proud of their professional filth, revolted at this, however and finally managed to do their work with dirty hands again. The incidence of childbed fever climbed as rapidly as it had fallen—but that didn’t bother the doctors.
The crucial moment came with the work of the French chemist Louis Pasteur (1822–95). Although he was a chemist his work had turned him more and more toward microscopes and microorganisms, and in 1865 he set to work studying a silkworm disease that was destroying France’s silk industry. Using his microscope, he discovered a tiny parasite infesting the silkworms and the mulberry leaves that were fed to them. Pasteur’s solution was drastic but rational. All infested worms and infested food must be destroyed. A new beginning must be made with healthy worms and the disease would be wiped out. His advice was followed and it worked. The silk industry was saved.
This turned Pasteur’s interest to contagious diseases. It seemed to him that if the silkworm disease was the product of microscopic parasites other diseases might be, and thus was born the “germ theory of disease.” Fracastoro’s invisible infectious agents were microorganisms, often the bacteria that Cohn was just bringing clearly into the light of day.
It now became possible to attack infectious disease rationally, making use of a technique that had been introduced to medicine over half a century before. In 1798, the English physician Edward Jenner (1749–1823) had shown that people inoculated with the mild disease, cowpox, or vaccinia in Latin, acquired immunity not only to cowpox itself but also to the related but very virulent and dreaded disease, smallpox. The technique of “vaccination” virtually ended most of the devastation of smallpox.
Unfortunately, no other diseases were found to occur in such convenient pairs, with the mild one conferring immunity from the serious one. Nevertheless, with the notion of the germ theory the technique could be extended in another way.
Pasteur located specific germs associated with specific diseases, then weakened those germs by heating them or in other ways, and used the weakened germs for inoculation. Only a very mild disease was produced but immunity was conferred against the dangerous one. The first disease treated in this way was the deadly anthrax that ravaged herds of domestic animals.
Similar work was pursued even more successfully by the German bacteriologist Robert Koch (1843–1910). Antitoxins designed to neutralize bacterial poisons were also developed.
Meanwhile, the English surgeon Joseph Lister (1827–1912), the son of the inventor of the achromatic microscope, had followed up Semmelweiss’s work. Once he learned of Pasteur’s research he had a convincing rationale as excuse and began to insist that, before operating, surgeons wash their hands in solutions of chemicals known to kill bacteria. From 1867 on, the practice of “antiseptic surgery” spread quickly.
The germ theory also sped the adoption of rational preventive measures—personal hygiene, such as washing and bathing; careful disposal of wastes; the guarding of the cleanliness of food and water. Leaders in this were the German scientist Max Joseph von Pettenkofer (1818–1901) and Rudolph Virchow (1821–1902). They themselves did not accept the germ theory of disease but their recommendations would not have been followed as readily were it not that others did.
In addition, it was discovered that diseases such as yellow fever and malaria were transmitted by mosquitoes, typhus fever by lice, Rocky Mountain spotted fever by ticks, bubonic plague by fleas and so on. Measures against these small germ-transferring organisms acted to reduce the incidence of the diseases. Men such as the Americans Walter Reed (1851–1902) and Howard Taylor Ricketts (1871–1910) and the Frenchman Charles J. Nicolle (1866–1936) were involved in such discoveries.
The German bacteriologist Paul Ehrlich (1854–1915) pioneered the use of specific chemicals that would kill particular bacteria without killing the human being in which it existed. His most successful discovery came in 1910, when he found an arsenic compound that was active against the bacterium that causes syphilis.
This sort of work culminated in the discovery of the antibacterial effect of sulfanilamide and related compounds, beginning with the work of the German biochemist Gerhard Domagk (1895–1964) in 1935 and of antibiotics, beginning with the work of the French-American microbiologist René Jules Dubos (1901–[1982]) in 1939.
As late as 1955 came a victory over poliomyelitis, thanks to a vaccine prepared by the American microbiologist Jonas Edward Salk (1914–[1995]).
And yet victory is not total. Right now, the once ravaging disease of smallpox seems to be wiped out. Not one case exists, as far as we know, in the entire world. There are however infectious diseases such as a few found in Africa that are very contagious, virtually 100 percent fatal, and for which no cure exists. Careful hygienic measures have made it possible for such diseases to be studied without their spreading, and no doubt effective countermeasures will be worked out.
New Disease
It would seem, then, that as long as our civilization survives and our medical technology is not shattered there is no longer any danger that infectious disease will produce catastrophe or even anything like the disasters of the Black Death and the Spanish influenza. Yet, old familiar diseases have, within them, the potentiality of arising in new forms.
The human body (and all living organisms) have natural defenses against the invasion of foreign organisms. Antibodies are developed in the bloodstream that neutralize toxins or the microorganisms themselves. White cells in the blood stream physically attack bacteria.
Evolutionary processes generally make the fight an even one. Those organisms more efficient at self-protection against microorganisms tend to survive and pass on their efficiency to their offspring. Nevertheless, microorganisms are far smaller even than insects and far more fecund. They evolve much more quickly, with individual microorganisms almost totally unimportant in the scheme of things.
Considering the uncounted numbers of microorganisms of any particular species that are continually multiplying by cell fission, large numbers of mutations must be produced just as continually. Every once in a while such a mutation may act to make a particular disease far more infectious and deadly. Furthermore, it may sufficiently alter the chemical nature of the microorganism so that the antibodies which the host organism is capable of manufacturing are no longer usable. The result is the sudden onslaught of an epidemic. The Black Death was undoubtedly brought about by a mutant strain of the microorganism causing it.
Eventually, though, those human beings who are most susceptible die, and the relatively resistant survive, so that the virulence of the diseases dies down. In that case, is the human victory over the pathogenic microorganism permanent? Might not new strains of germs arise? They might and they do. Every few years a new strain of flu rises to pester us. It is possible, however, to produce vaccines against such a new strain once it makes an appearance. Thus, when a single case of “swine flu” appeared in 1976, a full scale mass-vaccination was set in action. It turned out not to be needed, but it showed what could be done.
Copyright © 1979 by Isaac Asimov, A Choice of Catastrophes: The Disasters That Threaten Our World, originally published by Simon & Schuster. Reprinted with permission from the Asimov estate.
[This article was originally published on June 8th, 2020 as part of a standalone magazine called GOOD10: The Pandemic Issue. Produced as a partnership among LeapsMag, The Aspen Institute, and GOOD, the magazine is available for free online.]
