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Immunity, hygiene measures, virus mutations… How did the various epidemics end in history?

2022-01-12T09:16:41.694Z


Smallpox, cholera, Spanish flu, and more recently SARS or Ebola, the major infectious diseases of contemporary times have mostly died out.


Could there be "

a possibility

" that this fifth wave is "

the last

"?

The Minister of Health Olivier Véran was recently optimistic.

"

It is likely that we have all acquired some form of immunity

," he said.

Read also Epidemics, wars, national funerals ... Notre-Dame de Paris has always shared the fate of the French people

With a very high rate of circulation of the virus, which for two years has killed more than 5.5 million people on the surface of the globe, the hypothesis of even partial collective immunity making it possible to put an end to the pandemic is not not so improbable in view of the history of past major epidemics.

The Spanish flu, collective immunity

The Spanish flu, for example, which is the biggest pandemic of the 20th century (between 20 and 50 million deaths), raged in three waves between the spring of 1918 and the spring of 1919, and then endemically in the 1920s. Almost one in two people have been infected on the planet. "

The disease has spread so widely throughout the entire population of the world, from the Inuit of northern Canada to South America, that there has undoubtedly been some form of herd immunity against this influenza strain of type H1N1

”, explains Professor Philippe Santeonni, microbiologist at the Institut Pasteur and the Collège de France.

The researchers' hypothesis is that the Spanish flu virus, with what epidemiologists call the harvest effect, no longer had enough unimmunized hosts to spread.

"

We also see in the 1920s that tuberculosis is regressing, because, according to some researchers, this disease had a potential stock of patients considerably reduced following the death by influenza of all those who had a fragile lung

", explains Laurent-Henri Vignaud, science historian.

An Italian hospital during the Spanish flu epidemic.

Costa / Leemage

However, it remains difficult to determine precisely all the factors that led to the extinction of a disease, especially since at the time, there were not all the current instruments to identify virus mutations. .

If we know that mortality has changed between the different epidemic waves of the Spanish flu, we cannot say today whether there have been viral changes

,” reports Philippe Santeonni.

Break transmission chains

These mutations have all their importance in the end of an epidemic because the characteristics of a virus, and first of all its transmissibility define its ability to survive in a population. SARS disease (severe acute respiratory syndrome) for example, which was responsible for around 8,000 cases and nearly 800 deaths between 2002 and 2004, was not very transmissible. In addition to that, "

the infected people were contagious at the peak of the disease, when they were already isolated or in the hospital

", specifies Philippe Santeonni. Tracing the chains of contamination and quarantine measures were essential in eradicating this epidemic which has been extinguished in large part thanks to human action.

Read alsoVaccine-skeptical France, a historic "incongruity"

The Ebola virus, the first case of which was identified in 1976 and at the origin of a first major epidemic from December 2013 in West Africa, "

was also easy to contain

", reports Laurent-Henri Vignaud .

If the virus is not transmissible by air, it is especially the symptoms of the disease - hemorrhagic fevers in particular - which made it possible to set up health cords quickly.

Ebola is not a silent disease, it is clearly identifiable and mortality is very rapid

”.

Smallpox vaccination

Other diseases that have marked history have been largely eradicated by the vaccine.

Smallpox, or smallpox, is one such example.

Viral in origin, it looks like a pustular dermatosis, which can look like a severe form of chickenpox characterized by small pustules.

The rash covers the whole body, including the face.

It is usually accompanied by fever, pain and delirium.

If the number of victims is difficult to estimate from a global point of view, smallpox is the cause of hundreds of thousands of deaths, in France alone.

King Louis XV, for example, died of it.

Plate by Edward Jenner (1798) showing a hand covered with boils.

British Library / Robana / Leemage

In the United Kingdom, the smallpox vaccine was made compulsory in 1853. In France, it was imposed in the army in 1888 and made compulsory with the booster in 1902. Vaccination rates quickly reached 70% but the final phase of eradication was complicated.

It took a major WHO campaign after World War II and a surveillance and containment strategy before the disease officially died out in 1979. “

Since total vaccination is often too difficult to implement, this strategy consisted of isolating the cases and vaccinating all those who lived in the vicinity of the outbreaks

, ”notes Philippe Santeonni.

Cholera

Another essential factor in the case of cholera has been the improvement of hygienic conditions. Cholera is an intestinal disease. It appeared on French territory in 1832, after passing through India, Russia, Poland and Germany. Wastewater treatment plants, very different from those we know today, allow the bacteria to spread through water, contaminated by the stools of infected people. "

There is a real reflection in the 19th century, stemming from the hygiene of the 18th century, to understand the nature of the threat and the relevance of improving hygiene conditions

", explains Laurent-Henri Vignaud. For the record, it is at this time that we get into the habit of putting lemon (or vinegar) in oysters.

The disease was eradicated in France also thanks to a vaccine which was developed in the wake of the work of Pasteur, at the end of the 19th century, "

and by a certain immune habit, the disease circulating widely in the world

", notes l 'historian.

Read alsoThese diseases that have killed well over 100,000 people in France

Health policies have therefore often played a primordial role in the eradication of the major diseases of the contemporary era. The natural course of disease in populations has also had an impact on whether or not immunity is offered to infections or mutations. In the case of the current coronavirus, "

this combination of approach must be adopted

", pleads Professor Philippe Santeonni. "

We are in an acceleration of time that people are not aware of

», Recalls Laurent-Henri Vignaud.

Looking back on history, our two-year war against Covid-19 is nothing compared to the difficult and winding diplomacy with which the men of past centuries have had to play to coexist with the epidemics that have often spread over decades.

Source: lefigaro

All news articles on 2022-01-12

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