The Black Death

Medical coding in its earliest form started as an attempt to avoid the Black Death. The bubonic plague, caused by the bacteria Yersinia pestis, arrived in Sicily via ship rats in 1347. It spread rapidly, reaching England in 1348. Almost half the city of London’s population of 70,000 died of the disease over the next 2 years. Given that life expectancy at the time was about 26 years and about 35% of children died before the age of 6, the Black Death contributed to the increased demise of the already death-ridden populace.

Italian author Giovanni Bocaccio lived through the plague in Florence in 1348. In his book The Decameron (1921), he describes how the Black Death got its name:

In men and women alike it first betrayed itself by the emergency of certain tumors in the groin or the armpits, some of which grew as large as a common apple…. The form of the malady began to change, black spots or livid making their appearance in many cases on the arm or the thigh or elsewhere, now few and large, then minute and numerous. These spots were an infallible token of approaching death.

The plague was highly contagious. As soon as people realized that contact with the sick could mean death, they isolated themselves. As Bocaccio describes:

Citizen avoided citizen, how among neighbors was scarce found any that showed fellow-feeling for another, how kinsfolk held aloof and never met. Fathers and mothers were found to abandon their own children, untended, unvisited, to their fate, as if they had been strangers.

Once the initial scourge was over, isolated outbreaks of plague continued in Europe throughout the next 3 centuries. It became an increasingly urban disease due to poor sanitation and crowded living conditions. The Great Plague of 1665 killed 25% of London’s population.  illustrates the garb worn by “plague doctors,” who filled the beak area with herbs that were thought to ward off the Black Death.

The London Bills of Mortality, shown in , were published weekly, and as of 1629 included the cause of death. Information was collected by parish clerks in various geographic areas. In order to determine which areas had the most cases of plague, Londoners purchased copies of the Bills and tracked the spread of the disease from one parish to another in order to avoid it. During one week in 1665, when the total number of London deaths was 8,297, bubonic plague accounted for 7,165 of those deaths.

Causes of death found in the Bills include diseases recognized today, such as jaundice, smallpox, rickets, spotted fever, and plague. Other conditions have creative descriptions, such as “griping in the guts,” “rising of the lights” (croup), “teeth,” “king’s evil” (tubercular infection), “bit with a mad dog,” and “fall from the belfry.”

John Graunt, a London merchant, published Reflections on the Weekly Bills of Mortality in 1665. Its central theme was that deaths from plague needed to be examined in the context of all the other causes of mortality in order to understand the effects of all diseases. The 60 disease categories in the Bills constituted the first systematic attempt to analyze the incidence of disease.

FIGURE 1-1 Plague doctor. The beak was filled with herbs thought to ward off the Black Death.

Courtesy of Wellcome Library, London.

FIGURE 1-2 London Bills of Mortality, 1665.

Courtesy of Wellcome Library, London.

It was at this point that the science of epidemiology, the study of epidemics, was born.

During the 18th century, additional classifications were authored by Linnaeus in Sweden (Genera Morborum, 1763), Bossier de Lacroix in France (Nosologia Methodica, 1785), and Cullen in Scotland (Synopsis Nosologic Methodicae, 1785). Nosology is the branch of medicine that deals with classification of diseases.

William Farr and the Cholera Studies

As the first medical statistician for the General Register Office of England, Dr. William Farr revamped the Cullen disease classification to standardize the terminology and utilize primary diseases instead of complications. Farr incorporated additional data into his classification, enabling reporting and analysis of factors such as occupation and its effect on cause of death.

Farr’s dedication to what he called “hygology,” derived from hygiene, was evident in his analysis of the London cholera outbreak of 1849. More than 300 pages of tables, maps, and charts reviewed the possible influence of almost every conceivable death-related factor, including age, sex, rainfall, temperature, and geography. Even day of the week and property value were examined (Eyler, 2001).

The single association consistently present was the inverse relationship between cholera mortality and the elevation of the decedent’s residence above the Thames River. Unfortunately, this led Farr to the erroneous conclusion that the air was more polluted lower by the river, causing the transmission of cholera. He later converted to the correct waterborne germ theory of the disease after conducting a study during a second epidemic in 1866, which included data about the source of drinking water for those who died.

International List of Causes of Death