What is a zoonosis?

THE ESSENTIAL

  • There are more than 200 types of zoonoses and it is estimated that they account for 60% of infectious diseases. They affect 2.6 billion people each year.
  • There would remain 1.7 million zoonoses to be discovered in mammals and birds and more than 800,000 could infect humans.

Do you know the common ground between Covid-19, Ebola fever, bird flu, Zika and monkeypox? They are all zoonoses: infectious diseases transmitted to humans by animals. There are more than 200 types of zoonoses and it is estimated that they account for 60% of infectious diseases. They affect 2.6 billion people every year.

Many zoonoses can be deadly

Some zoonoses, such as rabies, are only transmitted by direct contact between animals and humans, such as a bite. But many of them affect animals first and can be transmitted from person to person on a large scale and create an epidemic. For example, avian flu passed from wild waterfowl to farmed birds and then spread to humans.

Many zoonoses are also transmitted to humans through mosquito bites, making it the deadliest human in the vertebrate and invertebrate world, with at least 725,000 deaths per year. They are vectors of diseases such as Zika, for example, but mainly malaria, of which 212 million cases were registered with 429 thousand deaths according to the World Health Organization. Bats and rodents are also the main vectors of zoonoses. Often, the pathogens that live in them do not harm them.

An old but growing phenomenon

Zoonoses are not a new phenomenon, measles and malaria have been known for hundreds of years. But it is a rapidly expanding phenomenon: according to some studies, three quarters of the infectious diseases that have emerged in the last thirty years are zoonoses. The reason ? Humans tend to get closer and closer to wild animals.

There are several causes for this: mainly deforestation, but also rampant urbanization and industrialization and the impacts of global warming on the environment (droughts, floods, forest fires, etc.) areas. Farm animals can then serve as relays for viruses or bacteria in the wild.

Trafficking and consumption of wild animals also increases the risks. The transmission of Ebola virus by wildlife has been linked in particular to the handling and slaughter of bushmeat.

The worst is probably yet to come

The worst thing is that many zoonoses can be discovered in the next few years. For viruses alone, a UN expert group estimates there are still 1.7 million to be discovered in mammals and birds, and more than 800,000 could infect humans.

The problem is that certain geographic areas are more prone than others to the transmission of infectious agents between species: Southeast Asia, North America, Sub-Saharan Africa, India… These are also the areas that will be heavily populated in the next few years by men. . This could make these places the starting point for future pandemics.


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