He says that zoonoses have multiplied in recent years. Vertebrate animals transmit diseases that can even become specifically human, such as Covid-19. According to the World Organization for Animal Health, about 60% of emerging diseases are of zoonotic origin.
Agriculture, travel and deforestation in question
Several elements lead to this phenomenon, in particular “the intensification of travel, which allows (diseases) to spread more quickly and in an uncontrolled way”, underlined Marc Eloit, head of the Pathogen Discovery laboratory at the Institut Pasteur. By occupying larger and larger areas of the globe, humans contribute to disrupting the ecosystem and encouraging the transmission of viruses. The intensification of industrial livestock farming also increases the risk of spreading pathogens among animals. The wildlife trade 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 are losing animals that naturally regulate viruses, which allows them to spread more easily,” explained Benjamin Roche, a biologist at the Institute for Research for Development (IRD), a specialist in zoonoses.
The threat of global warming
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, species will transmit their viruses more, which will promote the emergence of new diseases potentially transmissible to humans.
The study draws a future “network” of viruses jumping from species to species and growing as the planet warms. “A whole line of new and potentially dangerous 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 and the International Livestock Research Institute.
The main and recent diseases caused by zoonoses
The beginning of the 21st century was marked by several epidemics of emerging viruses linked to zoonoses. Caused by a new coronavirus, Sars-CoV-2 (whose origin remains unclear), Covid-19 emerged in late 2019 in China before spreading around the world, killing more than 6.2 million people. end of May 2022, from the American Johns Hopkins University.
Similar to and originating in China in 2002, the Severe Acute Respiratory Syndrome (SARS) virus was transmitted from bats to humans via civets, a wild mammal sold at the time in Chinese markets for its meat. Also in the realm of coronaviruses and first detected in 2012 in Saudi Arabia, Middle East Respiratory Syndrome (MERS) is a viral respiratory disease caused by a novel coronavirus transmitted by camels. It caused the death of a third of the infected cases, with 850 victims in total.
Still linked to bats, and first identified in 1976 in the Democratic Republic of Congo, the Ebola virus triggered a series of epidemics in 21st century Africa that claimed the lives of more than 15,000 people in total. From the same family, the Marburg virus – a serious disease that causes severe hemorrhagic fever – emerged in 1967 in Germany and Yugoslavia after work with green monkeys. It causes the death of approximately 50% of those infected.