Good year, bad year, in the middle of the XIXand century, one pregnant woman out of six, or even one out of five, died of puerperal fever after giving birth in one of the two obstetrics departments of the Vienna General Hospital. The second service recorded only a mortality rate of 3% for this scourge of hospital maternity wards, attributed at the time to the poor ventilation of the rooms as well as the promiscuity of the patients.
Both departments used basically the same equipment and saw the same type of patients. On the other hand, doctors practicing or in training provided care in the first case while midwives took care of the second unit.
By dint of observation, the Austro-Hungarian obstetrician doctor Ignace-Philippe Semmelweis (1818-1865) eventually understood that practicing doctors transported “particles of contamination” from corpses in autopsy rooms to the obstetrics department. . He also demonstrated that washing hands with hypochlorite radically reduced the rate of contamination and mortality of patients.
The theory of microbial diseases did not yet exist. The capital etiological discovery of the Viennese doctor will be disputed, and hand washing will take time to impose itself. The “Semmelweis effect” designates from the tendency to reject evidence that upsets established beliefs, to blocking the discovery of an important scientific fact, or even punishing its discoverer.
Time and reason have done their work, and “the invention of hand washing” holds everywhere and again during the current pandemic. In fact, Doctor Semmelweis (died of ill-treatment in an asylum) is now recognized as one of the fathers of modern epidemiology, explains the specialist in the history of medicine Pierre-Olivier Méthot in telling this astonishing anecdote.
“His scientific approach based on observation and his use of statistics and control groups will nevertheless have a following,” he says. We are not yet talking about epidemiological science as we know it in the twentiethand century, but the step taken is very important. »
The Hippocratic Oath
Epidemiology studies health problems in a given population by looking for factors that influence the onset and distribution of disease. This fairly marginal branch of medicine has suddenly become central for two years of the pandemic.
Professor Méthot finds himself perfectly placed to shed light on the birth and development of this discipline. He holds the new Canada Research Chair in Medical Humanities and History of Biological Thought attached to the Faculty of Philosophy at Université Laval. This is the first chair of its kind in French in the country.
The medical humanities take medicine and life sciences as an object of study, but they also aim to transmit non-medical knowledge to future doctors. This additional rifle training is compulsory in several countries. Quebec has fallen behind in this regard, according to Professor Méthot.
The philosopher, a specialist in the history of medical ideas and practices, traces his interest in the health of populations back to Hippocrates. The father of medicine already linked, almost 2500 years ago, environmental factors and lifestyles (including diet) to human illnesses.
“At that time, we did not think of forming large groups of individuals,” explains the Quebec professor. Each case of illness is then distinct in its causes and effects. Health was truly individualized in Antiquity, even if the role of the environment was recognized from the outset. But then there is no populational thinking. »
The influence of Hippocrates will extend until the XIXand century, and the Semmelweis effect is partly explained by the strength of the old miasma-centric paradigm. Medicine will begin to take an interest in populations (and not only individuals) first with the great plagues, then in the 17th century.and century with the Bills of Mortality by John Graunt, ancestors of our daily assessments of the current pandemic.
The risk society
The great mutation of epidemiology came from researchers in biostatistics in the XXand century, especially the British, including Karl Pearson, Ronald Fisher and, more particularly, Austin Bradford Hill (1897-1991), father of randomized clinical trials, a very important methodology for the development of vaccines, including those against COVID-19. He also gave his name to criteria for moving from correlation to causation. It determines nine of them (including the strength of the association, its stability, its specificity, etc.). These criteria are established as part of a 1960s survey of tobacco smoke as a source of lung cancer.
Long-term study also appeared after the Second World War. The first, that of Framingham (a town in Massachusetts near Harvard University), focusing first on cardiovascular risk, launched in 1948, admitted its third generation of participants in 2002. The accumulated epidemiological work includes thousands of scholarly articles.
“This step marks a major break from description to etiology,” says Professor Méthot. Instead of focusing on entire populations […] we will study groups of individuals formed to make precise observations according to the causes that we seek to understand. Since the 1950s, epidemiology has carried out surveys of control cases to determine risk factors, for example tobacco consumption. The risk factor is the key term to distinguish the modern discipline. »
We have seen this with the management of the current crisis. “Risk, which has a long history, is becoming a central concept in contemporary medical thought,” explains the professor. We try to measure it, to predict it. We manage the risk on a daily basis in this pandemic. »
Insurance company actuaries are also obsessed with it. Genetics, the master science of recent decades, has introduced new risk factors. It has also helped to shift the focus of studies on the individual. We have seen the effects of this in studies that have highlighted the comorbidity factors of COVID-19: older people, or obese people, run a higher risk of developing severe forms of the virus.
Cantilever
The discipline is now embodied in known and recognized personalities. Each society has its Horacio Arruda, its Nimâ Machouf, its Theresa Tam.
Epidemiologists recommended lockdowns, curfews, school closures, and got them. Few leaders have dared to disobey them, like President Donald Trump, in constant tension with the Dr Fauci.
“Several observers have underlined the too great proximity of the national director of public health of Quebec with the power, says professor Méthot. Epidemiology enjoys increased visibility and epidemiologists have gained a say in society that they did not have before. This position stems from an exceptional, global situation that affects all spheres of society. Even AIDS did not have such an impact. »
Having noted this, it must also be recognized that, just before the crisis, Public Health remained marginal and unloved, little listened to and underfunded, not only in Quebec, even as pandemic pathologies were developing (SARS, Ebola, etc. ). Which gives quite a contrast: a science based on risk factors has been ill-prepared by the public authorities to face an immense pandemic risk.
“It is from epidemiology that the mathematical models of the evolution of diseases have been developed and that the recommendations for action have been able to be deployed since the spring of 2020, explains, in conclusion, Professor Pierre-Olivier Méthot. But Public Health, which bases its recommendations on epidemiology, always finds itself sitting between two chairs: if it does not do enough, it is criticized for having been slow to act; if she overdoes it, she is accused of being an alarmist. In any case, what took everyone by surprise was to see the poor state of public health in each of the countries when the pandemic hit. »