Coronavirus has become a household name after the current COVID-19 outbreak. The virus has been identified as a positive sense single-stranded RNA virus and has the technical name, SARS-CoV2. It is also well known that it is highly contagious and is transmitted between humans through coughing and sneezing via respiratory droplets. Scientists have a pretty good understanding of what causes the COVID-19 disease and how it spreads through the population, which makes it easier for people to understand the concept and purpose of social distancing and quarantine. But in ancient times, ideas about the cause of diseases were entirely speculative and there were many interesting theories before the germ theory of diseases was established in the late 1800s.
Supernatural Theory
Unsurprisingly, the earliest theory was that diseases were caused by supernatural forces. People believed that when gods became angry they unleased their fury upon mankind by sending diseases to cause suffering. For example, according to Greek mythology, Zeus became angry with humanity when they accepted the gift of fire from Prometheus, so he created a box stuffed with all the diseases, sorrows, and crimes that afflict humanity and gave it to Pandora’s husband, Epimetheus. Pandora was curious to know what was inside the box and opened it, letting out all the diseases of the world.
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| Pandora's box depiction. Image: Quatr |
Ancient Egyptians also believed that disease was caused by gods and spirits. A predominant belief was that spirits blocked channels in the body which caused disease. This blockage could be reversed by prayers and natural remedies. Egyptians therefore had thousands of magical remedies and incantations, not to cure disease, but to repel demons causing it.
Humorism and Miasma Theory
Hippocrates’ theory of humorism claimed diseases were caused by changes in the harmony of the four humors present in the body: blood, phlegm, yellow bile and black bile. Greek historian Thucydides proposed the miasma theory while describing the Plague of Athens, a theory later popularized by Galen. It was the dominant belief until the mid nineteenth century. Miasma which meant pollution in ancient Greek, was defined as bad air or a poisonous vapor that arose from decomposed organic matter. The immediate surrounding of a sick person would therefore, contain the miasma and transmit the disease to others. In fact, the name of the disease malaria comes from
mala aria, which translates to “bad air” in medieval Italian.
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| Miasma representation by Robert Seymour. Image: National Library of Medicine |
Although the miasma theory did not identify what the contagions in the air were, they did have some basis in the eventual germ theory. Galen speculated that plagues were caused by “seeds” present in the air. The great Roman scholar Marcus Terentius Varro speculated that swamps contained minute creatures in the air that could enter the body through the mouth and nose. In some ways, his theory could be considered the first germ theory ever proposed, but Galen was so prominent that his beliefs took precedence over Varro’s and the miasma theory lasted for many centuries. In the middle ages, several Arab scholars proposed tiny contagions could contaminate food and water. But the Europeans again refused to believe the new theories in favor of the miasma theory.
Germ Theory
Modern germ theory finally began to form in the late 1800s after the work of Louis Pasteur and Robert Koch. It was in 1890 that the existence of viruses was discovered. It quickly led to the establishment of the germ theory, and the identification of other germs or pathogens, such as bacteria and fungus, that caused various diseases.
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| Common pathogens. Image: Immerse Education |
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