Viruses and the Jewish Microbe Hunters

March 11, 2020

The Netherlands in the 17th century was a country of great tolerance, having welcomed the Jews (including renowned physicians) driven out of Spain and Portugal. This was the Dutch Golden Age, a time of breathtaking advances in the arts and sciences. It was there that the first microscopes were invented. It was thanks to the microscope that in the 1670s in the town of Delft, Antoni van Leeuwenhoek discovered a veritable zoo of subvisible microorganisms previously inconceivable to even the most fevered imagination.

Throughout the 18th century and well into the 19th, there was speculation among medical men about the possible relation of microorganisms to disease. Certain varieties of these tiny beings seemed to appear in the organs or blood of patients with certain diseases. But there were endless questions:

Could these creatures, so primitive, come into being by themselves (“spontaneous generation”)?

Were they the cause of disease or were they the product of the diseased body?

Could a pathogenic microbe of one disease transform into that of another disease?

In diseases known to be infectious, were microorganisms the culprits, transmitted from a diseased body to a healthy one, left there to germinate?

A breakthrough heralding the heroic age of the “microbe hunters” came in 1840 with the publication of “Pathological Researches” by the Bavarian doctor Jacob Henle, a descendent of rabbis. Using technologically advanced microscopes and deductive analyses of case histories, Henle declared to the medical world: “Contagion is matter endowed with individual life which reproduces itself in the manner of animals and plants, which can multiply by assimilating organic material and can exist parasitically on the sick body.”

A year later, Dr. Robert Remak, a Polish-German Jew, published the first of his observations that cells — of any living organism, including microbes — can arise only by division of parent cells. Thus, Remak helped put to rest the concept of “spontaneous generation.”


Humankind’s war against transmittable diseases accelerated dramatically in the second half of the century. In 1872, in the German city of Breslau (today’s Wrocław, Poland), the botanist-microscopist Dr. Ferdinand Cohn published his “Bacteria, the Smallest Living Organisms.” As the undisputed master of the classification of subvisible life, Cohn elucidated that while a microorganism of one disease may undergo various transformations, it remained the microorganism of that specific disease and not of another.

Robert Koch, a student of Henle and protégé of Cohn of Protestant background, discovered the tuberculosis bacterium and elucidated the mysterious life cycle of the anthrax bacillus.

Such dramatic advances led to the discovery of links in the chain by which the various pathogenic microorganisms are transmitted, and then to measures to break those links: cholera by drinking water contaminated by sewage, sleeping sickness by the tsetse fly, childbed fever by the contaminated hands of doctors and midwives, and malaria (literally “bad air” in Italian) by mosquitoes.

To such defensive measures were added an arsenal of aggressive weapons. In Berlin in the 1890s, Jewish doctor Paul Ehrlich was instrumental in developing serums. The watery part of the blood (after coagulation) of an animal, which has fought off a toxin-producing disease such as diphtheria, contains powerful antitoxins, which can be injected into a diphtheria patient. A brilliant and imaginative chemist, Ehrlich pioneered techniques for selectively staining specific microorganisms to distinguish them under the microscope. This principle inspired him to develop the world’s first chemotherapeutic agent — the arsenical compound Salvarsan, known popularly as the “magic bullet,” which homed in on and destroyed the spirochetes of syphilis. (Ehrlich’s fellow Jew Albert Wassermann developed the blood test for the disease.)

A general optimism prevailed as the new century dawned that humankind would soon be free of all serious infectious disease.

But there was a missing piece in the puzzle.


It had been known since ancient times that people who survived a given disease were wholly or partially immune from an attack by the same disease. In 1798, the English physician Edward Jenner showed that deliberate inoculation with the pustules of relatively benign cowpox (“vaccination,” from Latin vacca, cow) protected the person from attack from the far more virulent and deadly smallpox.

Among the great triumphs in the war against transmissible disease was the development of a new kind of vaccination by the French chemist Louis Pasteur, a devout Catholic. Pasteur showed how inoculating a patient with killed or attenuated (weakened by drying or other techniques) pathogens such as rabies, activated the natural immune system against a subsequent all-out attack by the fully virulent disease.

But here was the rub. Unlike the microorganisms of tuberculosis, cholera, diphtheria, syphilis and so many other diseases, no one had ever seen the agents of smallpox and rabies. Pasteur speculated that they were microorganisms beyond the range of the most powerful microscopes.

AIDS, hepatitis, SARS, Ebola and now coronavirus, new virulent viruses keep emerging. And the weapons to fight them — vaccines, tests, serums, pharmacological “magic bullets” — are in the enduring spirit of the great Jewish microbe hunters.

Around the turn of the 20th century, the Dutch microbiologist Martinus Beijerinck showed how the fluid of an infected plant after being strained through the finest filter was able to infect healthy plants. This was an important breakthrough, but Beijerinck erred in assuming the culprit wasn’t composed of solid matter. He called it “virus,” Latin for poison.

That no one had seen a virus made the fight more difficult. Between 1918 and 1920, as the Spanish flu claimed more lives than all the battlefields of World War I in the preceding four years, the medical profession mistakenly attributed it to an opportunistic bacterium, visible under the microscope.

The limit of what could be seen was dramatically pushed back with the invention of the electron microscope in the early 1930s, by which viruses, hundreds of times smaller than bacteria, were exposed to the light of day. It appeared that Pasteur was right after all in postulating that the agent of rabies was a microorganism.

But not quite. Research later in the century showed that viruses, unlike living entities (organisms), can’t multiply or reproduce on their own. Viruses turned out to be packets of genetic material — DNA or RNA —which penetrate, commandeer and destroy living cells in order to multiply.

Poliomyelitis, the dread crippler caused by an enterovirus, was checked in the 1950s (and is now virtually eradicated worldwide) thanks to two vaccines developed independently by the American Jewish medical doctors Jonas Salk and Albert Sabin. (The virus was cultured using the foreskins of circumcised babies.)

AIDS, hepatitis, SARS, Ebola and now coronavirus, new virulent viruses keep emerging. And the weapons to fight them — vaccines, tests, serums, pharmacological “magic bullets” — are in the enduring spirit of the great Jewish microbe hunters.

Frank Heynick lives in New York and has taught the history of medicine at New York University. He is the author of “Jews and Medicine: An Epic Saga.”

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