For several years now, we have been hearing about pandemics, endemics or even epidemics. But what is it all about? First of all, these terms are borrowed from the vocabulary of epidemiology, which is the study of the relationships between diseases and the factors likely to exert an influence on their frequency, their distribution, their evolution, and evoke an infectious disease. . Remember that an infectious disease is a disease transmitted by a pathogenic microorganism whether it is a bacterium, a virus or a parasite. A communicable or contagious disease is a disease which passes from an affected subject to a healthy subject.

How to avoid the transition from an endemic state to epidemic or even pandemic?

Endemic (from the Greek endemia = stay) is defined by the usual presence of a disease, generally infectious in a determined population or a specific region, with a stable incidence. For example, malaria is endemic in many African countries, just as hepatitis A is endemic in Thailand. Yellow fever is an endemic that has wreaked havoc in the tropical regions of Africa and South America, which is why it is necessary to get vaccinated before traveling to these countries. An endemic disease will affect more people than an epidemic or even a pandemic.

An epidemic (from the Greek epi = above, demos = people) refers to the development and rapid spread of an infectious and contagious disease in a given region over a given period.

This is the case with the seasonal flu epidemic in France which only appears during the winter period. Initially the term epidemic only concerned infectious diseases such as influenza, measles, ebola or more recently Covid-19 which is part of viral epidemics. Epidemics can also be bacterial, such as tuberculosis or plague, or both viral and bacterial, such as meningitis.

A pandemic (from the Greek pan = all, demos = people) is a very large epidemic, which starts from a localized area and then spreads to the whole world. The term pandemic has nothing to do with the number of deaths caused by the disease in question.

History has kept the memory of several great pandemics, notably the Black Death in the 1918th century, which killed around half of the European population.The Spanish flu between 1920 and 50 claimed infinitely more victims (XNUMX million) than the Great War.

Pandemics arise during major imbalances linked to social and environmental changes over the course of history, such as agricultural revolutions, wars and trade, travel and great discoveries, the industrial revolution or globalization. It is the emergence of a new transmissible pathogen and a new disease caused by this new agent that promotes the birth of a pandemic.

Among the major pandemics are cholera, smallpox, tuberculosis, polio and H3N2 influenza (1968-1970). Currently, pandemic viral infections mainly concern AIDS and seasonal flu. And since 2003, three pandemics caused by the coronaviruses SARS, MERS and Covid19.

For a given disease, the transition from an endemic to epidemic or even pandemic state is possible if there is a disruption of equilibrium or a significant modification in the environment. This happens, for example, when deforestation or other environmental or climatic disturbances bring humans into contact with viruses or bacteria that exist endemic in certain animals. The transition from animal species to humans can then transform an endemic into an epidemic, as in the case of avian flu, Ebola virus or Covid-19.

What is contagiousness?

Contagiousness is the ability of a bacterium or virus to infect more or less people and the ease of transmission from infected people to healthy people.It depends on several factors that come together:

• how the pathogen spreads. A virus carried by the air passes more easily from person to person than a virus that remains on the ground or in water;
• the state of health of the infected person and the ability of their immune system to control their infection to a greater or lesser extent;
• the lifestyle of the infected person as well as too many social interactions. This principle is the basis of the social distancing measures put in place during certain pandemics or epidemics, such as the Covid19 epidemic.
• factors related to climate and environment (cold, humidity).

Health management consists of taking measures to control a disease whether it is endemic, epidemic or pandemic, first at the local level, then nationally or even globally.

These measures can be individual in order to empower populations:

• use of condoms against HIV;
• enhanced personal hygiene (hand washing);
• wearing a mask to avoid projections (Covid-19);
• greet without shaking hands or kissing;
• avoid unnecessary travel and gatherings;
• get vaccinated if a vaccine exists.

In the XNUMXst century, the surveillance and control of a pandemic relies primarily on international cooperation. To end on an optimistic note, remember that a number of pandemics have been eradicated through vaccination. This is the case with smallpox, polio and tuberculosis.