In the mid to late nineteenth century, scientific patterns emerged which contradicted the widely held miasma theory of disease. These findings led medical science to what we now know as the germ theory of disease. Germ theory proposes that microscopic pathogens capable of replication (bacteria, viruses, etc.) are the cause of particular illnesses in both humans and animals. Prior to germ theory, people knew that diseases spread between humans, especially where many congregate, such as in armies and cities; but it was widely thought that this happened primarily due to exposure to unhealthy air (miasma) emanating from the sick or from people in general, as well as from swamps and conditions strongly influenced by climatic circumstances. Though there were a few early thinkers that suggested the possibility of microorganisms causing disease, it was not until the mid to late nineteenth century when several noteworthy figures made discoveries which would provide more efficient practices and tools to prevent the spread of communicable disease.
Contagion by means beyond miasma Led by stark statistical patterns, Ignaz Semmelweis and John Snow independently conceived of contagion of disease by means other than noxious air (miasma). Similarly, Florence Nightingale greatly decreased the prevalence of infection by implementing better hygienic practices.
Ignaz Semmelweis
Ignaz Semmelweis was a Hungarian obstetrician who began assisting Johann Klein at Vienna General Hospital's first two maternity clinics (also called a "lying-in wards") in 1846. Semmelweis became concerned with the number of women dying from a febrile illness called puerperal fever, colloquially referred to as "childbed fever." Childbed fever often occurred in the first few days after giving birth. This condition caused fever, intense abdominal pains, profound weakness, and ultimately death for many who acquired it. In the 1840s, when Semmelweis began his career in obstetrics, an expectant mother entering a maternity ward had a 10-20% chance of dying from this particular illness or complication. For some areas in Europe, the figure was greater with an estimated death rate as high as 30%. Childbed fever was an epidemic at the time which made labor and delivery a major cause of distress for families.
One of the clinics he oversaw was run by physicians and medical students, while the other was operated by midwives. Semmelweis noticed the midwife clinic had a significantly lower mortality rate. This compelled him to study the techniques and practices of both clinics in great detail to find the distinguishing factors between the two. Detailed autopsies of the women who died on the ward were performed in the mornings at the clinic. Despite his attempts to find a major difference between the clinics, Semmelweis concluded the same procedures and practices were used at both clinics.
The first clue came in 1847 in the form of tragedy for Semmelweis. A good friend of his at the clinic, Jakob Kolletschka, died after performing an autopsy with a cut on his hand. The cut was sustained from a medical student accidentally slitting his hand with a scalpel during the procedure. This friend had similar symptoms and post-mortem pathology to the mothers who died of childbed fever. Medical students performed autopsies prior to delivering babies, but the midwives only participated in labor and delivery care. Semmelweis then made the connection that left over pieces of a dead body could be transmitted via physician's hands into a live body and cause illness. The bacteria which caused childbed fever in Semmelweis's medical clinic was Streptococcus pyogenes. Though he did not have knowledge of specific microorganisms like bacteria, he understood disease could be transferred from one body into another. He advocated for the changing of bedsheets for this reason.
Semmelweis then required a strict handwashing regimen at the clinic ran by physicians and medical students using chlorinated water and brushes to remove any cadaver particles from under their fingernails. This decreased the death rate from 11.4% at the clinic to 2.7%. No mothers died in March or August in 1848 after the introduction of the handwashing protocol. In 1860 Semmelweis published a book titled Etiology, the Concept, and the Prevention of Puerperal Fever, but it was met with backlash from physicians. The medical community deemed it to be offensive since doctors considered themselves to be high status and were therefore not dirty or carriers of disease (as miasma was understood to be connected to immorality).
Semmelweis did not live to see his findings contribute to the germ theory of disease. He began to become obsessed with speaking only about puerperal fever and developed Alzheimer's-type symptoms which led to him being placed in a mental institution in 1865. That same year, he died from sepsis after sustaining wounds at the asylum. The wounds were believed to be from an attempted escape or caused by beatings or abuse he endured while detained. After the germ theory was widely accepted, Semmelweis became a celebrated figure with several hospitals and institutions named after him. Roughly 14 years after his death, scientists began to support his ideas. He became known as "The father of hand hygiene" and "The savior of mothers."
John Snow
England had multiple cholera epidemics during the 19th century. The earliest outbreak in Britain occurred in 1831. In that year, 21,800 people died from cholera within the country. These outbreaks were first blamed on the poor because they were said to smell bad and be immoral. This population was believed to cause "bad air." Foul urban air at the time was the prevailing theory of how disease was transmitted (miasma theory).
John Snow was an anesthesiologist who became well respected after anesthetizing Queen Victoria using chloroform during the birth of one of her children in 1847. In 1854 when a deadly cholera outbreak occurred close to his home in London, his priorities changed. Snow became concerned and was determined to discover the origin of the cholera outbreak. Even though the germ theory had not been established yet, he felt the outbreaks were not caused by "bad air" infecting blood, but by something entering a person's gut. Snow determined that inhaling "bad air" would not result in intestinal disease.Coleman, Thomas. (March 13, 2019) Causality in the Time of Cholera: John Snow As a Prototype for Causal Inference. http://dx.doi.org/10.2139/ssrn.3262234
The 1854 outbreak was centralized in a suburb of London called Soho. The number of deaths were concerning enough that some families fled their homes to find a new location to live in London. Snow theorized in the late 1840s that cholera was transmitted through water in an essay titled On the Mode of Communication of Cholera. He specifically believed that it was the contamination of water which spread cholera. At the time, London's sewage system was rudimentary with unmaintained cesspools and the dumping of waste into the River Thames. Snow decided to start his investigation by plotting each public water pump located within the Soho district on a map. He then asked for recent death records and walked the area to find the homes and families of the victims. The victim's families were asked questions about their loved one's routines and he marked each death on the map he had created. The map revealed that Broad Street and the area near it had the most mortalities. On this street was the Broad Street water pump. The houses nearest to that pump were the most affected by the disease. However, Snow noted there were two places nearby that were not affected by the pump so he explored why this was the case. One of these places was a workhouse in walking distance to the pump. This workhouse saw 5 deaths from cholera yet had over 500 workers. He discovered this workhouse had its own private water well which employees drank from instead of the Broad Street pump. Another nearby brewery had no deaths, but the men were given free beer to drink throughout their work day. There were outlier deaths that Snow decided to investigate. These were deaths that occurred outside of the typical pattern on his map. Snow discovered a woman and her niece, though they lived miles away from the pump, died of cholera. After interviewing a surviving family member, he found out that she once lived in the area and she particularly liked the Broad Street water. Because of this, she sent a servant to this particular pump to get water for her. The niece had been over to her house and consumed water from the pump. Another outlier case involved two young school children who died, but lived on a different street which had its own source of water. However, these two girls used Broad Street to travel to their school and back. They were known to drink from the well during their walk. Snow had already postulated nearly a decade earlier that water was to blame for cholera epidemics, and this investigation strengthened his claim. He made connections between events and used visual empirical evidence to support his claims. He took a sample of water from the Broad Street pump and studied it under a microscope. Unlike other water sources, this pump's water contained an unknown microbe that resembled white wool. Later this bacteria was given the name Vibrio cholerae. It is now recognized as the bacteria which infects a person with cholera. Though the city was not fully convinced of John Snow's theory on cholera, they removed the handle on the pump when Snow asked. This decreased the death rate from cholera rather quickly even though the mortality rates were already in decline.
Later it was discovered that cracks in a nearby cesspool leaked fecal matter into the water at Broad Street. Modern medical science has labeled this transmission of disease as the fecal oral route. But at that time, this route of disease was unknown to both physicians and the public. A baby named Frances Lewis was believed to be the first case which caused the outbreak. Her birth and death certificate match the time of the outbreak. A doctor listed the cause of death as a diarrheal "attack." Her mother cleaned her diapers in buckets then threw the water into the cesspool which leaked into the water supply.
After his diligent investigation into the 1854 cholera outbreak, Snow became a member of the London Epidemiological Society. He published a second edition of his prior book On the Mode of Communication of Cholera in 1855. He did not live to see the establishment of the germ theory of disease in the late 1800s. He died of a stroke at the age of 45.
Florence Nightingale
Florence Nightingale, like the majority of people living in the Victorian time period, believed in the miasma theory of disease. Though she was a mathematician and statistician, she was asked by the British secretary of war to join a nursing service during The Crimean War. When Nightingale arrived in Scutari, Turkey, the conditions of the British army hospital were gruesome and putrid. She noticed the leading cause of mortality for soldiers was not battle, but rather infection and illness. Though she still believed at that time "foul air" caused disease (miasma theory), she began a cleaning protocol to improve the air quality. There were men and areas of the hospital covered in feces. The plumbing and sewer system were both broken and their water supply at the hospital was mixed with sewer water. There was an infestation of both vermin and insects. Nightingale reported these concerns to the British Sanitary Commission so they could help with these large items on her agenda to fix. She also implemented a laundry service for both bedsheets and clothing, she proposed handwashing procedures for nurses, patient bathing practices were introduced, clean bandages were obtained, and healthy meals were provided.