Like “chirurgical,” the word “miasma” comes from an earlier time in medical history. It may sound more familiar, however, because one of its definitions is still in use today. If you want to say something about the dangerous influence of drugs, you could state, “My best friend got caught up in the miasma of drug addiction.” Or if you want to describe how someone managed to change his social status against all odds, you could say, “After many years of hard work and determination, he was finally free from the miasma of poverty.” So this word is still useful to describe “a dangerous, foreboding, or deathlike influence or atmosphere” (dictionary.com) or “an influence or atmosphere that tends to deplete or corrupt” (merriam-webster.com).

But up until the end of the 19th century, miasma was also the name of a popular theory to explain the origin of diseases, especially those that erupted into epidemics: cholera, typhus, typhoid, and others that occurred with regularity, like malaria and tuberculosis. The miasma theory was based on observation, as were many other medical theories of the time. People living in squalid and crowded conditions and/or near swamps seemed
to be most prone to epidemics and other diseases. Therefore, it made sense that the cause of the diseases was the poisonous miasma (clouds of small particles) in the air coming from polluted water, rotten vegetation, animal carcasses, and human waste. In other words, bad environments generated bad air, which in turn triggered diseases.

The concept goes all the way back to ancient Greece and may still be found in some people’s belief that sleeping in fresh air is beneficial to one’s health. The miasma theory did, however, provide some benefits to 19th century citizens. In an effort to control the outbreak of epidemics, towns and cities drained swamps and marshes; sanitary reformers tackled the job of cleaning up the dirty, poorly built, and densely populated city neighborhoods that had sprung up during rapid industrialization and immigration. Their attempts to improve the air quality actually ended up accidentally destroying some of the real causes of the diseases.

The miasma theory, though obviously wrong, died a slow death. Even with the development of the germ theory of infection in the mid 1800s, some people clung to belief in what they could see and smell. It took the work of people like Louis Pasteur, who proved the existence of pathogenic organisms, and Robert Koch, who isolated the bacteria that cause cholera and tuberculosis, to pave the way  for general acceptance of the germ theory. Their pioneering work, and the work of many other dedicated scientists, led eventually to the containment of most of the killer diseases of earlier centuries.