Covid-19, Ebola, monkey pox… Why are epidemics increasing?

“The interface between humans and animals has become quite unstable,” said Dr. Mike Ryan, head of emergencies at the World Health Organization (WHO), a few days ago. “Emergence factors and disease amplification have increased,” he said. We’ve just seen this with smallpox, but not only, he warned.

This monkeypox – “monkeypox” in English – caused by a virus transmitted to humans by infected animals – most often rodents – is the most recent example of the multiplication of these zoonoses.

These are infectious diseases that vertebrate animals can transmit to humans. Some even end up becoming specifically human, like Covid-19.

According to the World Organization for Animal Health, approximately 60% of emerging diseases are of zoonotic origin.

Appearing thousands of years ago, since man intensified his interactions with animals by domesticating them, they have seen their frequency increase a lot in the last twenty or thirty years.


In question, “the intensification of travel, which allows them to spread more quickly and in an uncontrolled way”, underlined to AFP Marc Eloit, head of the pathogen discovery laboratory at the Institut Pasteur.

By occupying larger and larger areas of the globe, humans also contribute to disrupting the ecosystem and encouraging the transmission of viruses.

The intensification of industrial livestock raising thus increases the risk of spreading pathogens among animals. The wildlife trade also increases human exposure to the microbes they can carry. Deforestation increases the risk of contact between wild animals, domestic animals and human populations.

“When we deforest, we reduce biodiversity, we lose animals that naturally regulate viruses, which allows them to spread more easily,” Benjamin Roche, a biologist at the Institute for Research for Development (IRD), a specialist in zoonoses, told AFP.

Climate change will also drive many animals to flee their ecosystems to more habitable lands, warned a study published in Nature in late April. However, by mixing more, the species will transmit more of their viruses, which will promote the emergence of new diseases potentially transmissible to humans.

“We need improved surveillance in urban and wild animals so that we can identify when a pathogen has jumped from one species to another,” said Gregory Albery, an environmental health expert at Georgetown University in the United States and co-author of the study. . “And if the recipient host is urban or close to humans, we should be particularly concerned.”

“Be ready”

The study draws a future “network” of viruses jumping from species to species and growing as the planet warms.

“Today we have easy and fast means of investigation that allow us to react quickly in the event of the appearance of new viruses”, assured Marc Eloit, from the Pasteur Institute. “We are also able to develop vaccines very quickly,” as we have seen with Covid-19.

But “a whole line of potentially dangerous new diseases is likely to emerge. We will have to be ready,” warned Eric Fèvre, a professor specializing in veterinary infectious diseases at the University of Liverpool (UK) and the International Livestock Research Institute (Kenya).

This means, according to him, “emphasizing the public health of populations” in the most remote environments and “better studying the ecology of these natural areas to understand how different species interact”.

Since the early 2000s, the “One Health” concept has been introduced: it promotes a multidisciplinary and global approach to health issues with close links between human and animal health and the environment.

France also launched in 2021 the international initiative “Prezode”, which aims to prevent the risks of zoonotic emergencies and pandemics, strengthening cooperation with the most affected regions of the world.

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