Pandemic, what is it?

Pandemic (from the Greek. Paneverything and demo, people) denotes an epidemic that goes far beyond a simple community and a limited territory. A pandemic affects a continent or an entire planet and may have multiple outbreaks. This very large epidemic can spread over a limited period of time or last for a long time. AIDS pandemic is a typical example of a protracted pandemic that is still ongoing.

Philippe Sansonetti, physician, microbiologist, professor at the College de France and the Pasteur Institute, defines the term Science and the future in February 2022 during the Covid-19 pandemic: “The word ‘pandemic’ is appropriate for a specific situation: it is a major epidemic that affects many regions of the world, with a strong progression, causing exceptional levels of morbidity and mortality and, therefore, health consequences. sociological questions”. Aside from a major medical accident, pandemics seem like a “total social fact.” Throughout its history, mankind has repeatedly faced several serious epidemic crises. However, as paleoanthropologist Bruno Morey points out, “there are almost no national symbols or memorials (but this also varies by country) to commemorate these but deadly epidemics, quickly forgotten by the collective memory of the nation. Maybe because we consider these epidemic crises independent of our behavior? »

Some major pandemics in history

The history of mankind is marked by encounters with pathogens that have transformed into epidemics and pandemics. This phenomenon each time marked the populations in their flesh for several generations, only to be completely forgotten by the next generations.


Cholera is a purely human disease caused by a bacterium Vibrio cholerae, or “cholera vibrio”, with fecal-oral transmission. The disease, endemic to South Asia (the delta of the Ganges and the Brahmaputra), spread beyond its original focus at the end of the Middle Ages. Spreading throughout Asia, then Europe from 19as well as century, cholera becomes a pandemic. Between 1817 and 1992, seven cholera pandemics were identified. France was struck by “Asiatic cholera” in 1832 during a second pandemic that killed 19,000 people in six months. Closer to home, 1992 is the year a new variant of the bacterium is identified, B. cholera O139, which causes much more severe clinical forms. Because of this strain, the eighth cholera pandemic could have occurred, while the seventh did not completely disappear. The world is currently experiencing epidemic episodes, the most memorable of which was the case in Haiti, where the vibrio was accidentally brought by UN troops in 2010.

Three plagues

Plague has probably existed since ancient times, it is a bacterial disease transmitted by flea rodents. Bacteria in humans Yersinia plague causes three clinical forms: bubonic plague and its complications, septicemic plague, and finally pneumonic plague, which is easily transmitted by airborne droplets.

  • “The Plague of Justinian” or 1as well as A plague pandemic from Ethiopia has decimated the population of the entire Mediterranean since 541. To his contemporaries, the appearance of this disease was what we would today call an emergent disease.
  • great black plague (1347-1352) arrived from the Central Asian plateaus in the 1330s, transmitted from Asian animal reservoirs. The bacillus follows the Silk Road to spread to the Caspian Sea and then to the Black Sea, the Mediterranean Basin and Europe in general. Its final stage is Russia, where it broke out in 1352. It kills between 25 and 30 million people, the equivalent of 30% of the population of Europe at that time.
  • 3as well as plague pandemic this is what comes closest to defining a pandemic by its full planetary spread, as it eventually affects all continents. This bubonic-type plague began around 1840 in China, in Yunnan, and spread through all the shipping lanes of the time, spreading to Asia, Africa, and also to North America across the Pacific and to Brazil via Portugal. It ends around 1910, but several hearths regularly reappear in the world.

Yersinia plague still present in some regions of the world, sub-Saharan Africa, the Americas and Asia. The World Health Organization (WHO) has reported 50,000 human cases of plague between 1990 and 2020.

Influenza pandemics

  • “Spanish flu”. After the carnage of the First World War, the great so-called Spanish flu pandemic would claim between 20 and 40 million lives, and perhaps even up to 50 million deaths.. 500,000 people die in France. Three successive waves of varying intensity are more likely to strike a relatively intact population, usually young people. And what’s striking from the evidence is the rate at which this flu kills. In 2005, thanks to samples taken from bodies buried in permafrost in Alaska.the H1N1 type virus that caused the very first pandemic in the well as century completely sequenced and reconstructed in the laboratory.
  • “Asian flu” and Hong Kong flu. Subsequent pandemics have been relatively less severe. In 1957-58, the so-called “Asian” flu still killed almost 100,000 people in France in a few weeks, and from 1 to 4 million people in the world. This is a new strain of H2N2 that is circulating. In 1968-69, the so-called “Hong Kong” influenza (H3N2) began in the spring of 1968, in Hong Kong appeared in Europe at the end of 1968. It killed between 1 and 2 million people worldwide and 31,000 victims in France.
  • Influenza A (H1N1)v. In the early summer of 2009, WHO officially declared an influenza A (H1N1)v pandemic. The virus is derived from a combination of various avian, swine, and human influenza viruses. The pandemic is more moderate than expected and the WHO suspects it has overestimated the risk. It caused between 150,000 and 500,000 deaths worldwide. Influenza claimed more victims among healthy people, who were a priori little threatened by the flu.

Spanish flu victims in Kansas in 1918. Credit © National Museum of Health / AP / SIPA

AIDS, an ongoing pandemic

June 1981 marks the official start of the AIDS epidemic. The first cases were found in Americans and are attracting the attention of Western medicine. However, HIV infection appeared in the 1920s in Central Africa. Reports indicate the existence of a serious and epidemic disease leading to cachexia: slender disease. Some cases have been published in medical journals such as the Lancet. Thousands of Africans had already died from what would later be called AIDS.


SARS, or severe acute respiratory syndrome, is the first pandemic that emerged in 21as well as century (2003). For Arno Fontane, an epidemiologist of infectious and tropical diseases, this is even the “prototype of the epidemic of the 21st century.”as well as century” is quickly identified and then localized. For the researcher, SARS becomes a lesson for future pandemic scenarios: the virus’s crossing the species barrier is better understood; molecular epidemiology allows to refine the results of classical epidemiology with sequencing of viral, animal and human strains; Finally, we better understand the role of air transport in distribution. The SARS epidemic affects 35 countries. Index case, a tourist in a hotel in Hong Kong infects 13 travelers flying to six international destinations. end, 8,000 patients, including 800 deaths. There are seven “probable cases” in France, including one patient who died.virus monitoring tools are configured.

Covid-19 epidemic

The Covid-19 pandemic is another major turning point in the history of human epidemics. At the end of 2019, the number of cases began to multiply not only in China, but throughout the world. The dead number in the millions, the sick in the billions. Many of them will never be taken into account due to the lack of an effective review policy. Millions of survivors are living with the exhaustion and infirmities of the “prolonged covid”. The outbreak has put pressure on hospital systems and the national economy. Among the many medical lessons to be learned from the Covid-19 pandemic is a better understanding of virus transmission in smaller aerosols, knowledge to be applied to other respiratory illnesses such as the flu or the common cold.

At the very moment of the Covid-19 epidemic, other pandemics are still going on that we do not spontaneously perceive as such. Hepatitis C, chikungunya, the emergence of Lyme disease or the geographic distribution of dengue within our borders.

How to prevent the next pandemic?

Our health at the crossroads of wildlife and the environment. The impact of human activities on zoonoses, these species-crossing diseases, is a growing concern. Keep an eye on several animal reservoirs from which the pathogen may emerge. These reservoirs may come from livestock farms, areas deforested as a result of agricultural and urban expansion. Globalization, climate change and biodiversity loss complete the list of transmission risks. The One Health concept highlights our interdependence between human, animal and ecosystem health and aims to raise awareness of the risks of emerging diseases.

WHO action. In 2015, WHO started developing a search tool: a list of pathologies with high epidemic propensity. In 2018, Ebola, Zika, SARS and MERS were joined by disease X, caused by a hypothetical virus in the more or less near future. In the aftermath of the Covid-19 pandemic, international organizations such as the WHO became convinced that the international treaty on pandemics Prevention, preparedness and response efforts need to be coordinated, and countries must be committed to closer cooperation.

How do you know if the pandemic is over?

The end of the pandemic does not mean that the pathogen has completely disappeared. An epidemic will not necessarily go away when the virus or bacterium goes away. The pathogen may remain and the disease disappear because the population as a whole has reached a level of collective protection sufficient that it no longer circulates efficiently (vaccination or collective natural), or even because environmental conditions are not more favorable. to bacteria or viruses. As a result, you live with the pathogen.

The end of a pandemic is not determined solely on the basis of scientific observations., and according to social criteria: collective and individual behavior and political decisions. In other words “consensus opinion-based“The pandemic will be left behind when we stop caring about it?

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