COVID-19: May Be the Beginning of Massive Pandemics
The coronavirus epidemic that is affecting us right now may not be an isolated and historical episode. For many ecosystem observers and public health experts, the coronavirus epidemic is the tip of a much larger phenomenon.
The succession of pandemic crises caused by the collision of human and natural habitats. A major threat that creates an obligation to take into account not only the health of men, but also that of the planet.
Just a decade or two ago, it was widely believed that tropical forests and pristine natural environments teeming with exotic wild animals threatened humans by harboring viruses and pathogens that cause new diseases in humans, such as the Ebola, HIV, and Dengue viruses. But a number of researchers today believe that it is, in fact, humanity's destruction of biodiversity that creates the conditions for the emergence of new viruses and new diseases like Covid-19.
"We are invading rain forests and other wild landscapes, which are home to so many animal and plant species, and within these creatures, so many unknown viruses," writes David Quammen, author of Spillover: Animal Infections and the Next Pandemic, recently published. in the New York Times. He adds: “We are cutting the trees; We kill the animals or put them in cages and send them to the markets. We disrupt ecosystems and remove viruses from their natural hosts. When this happens, they need a new host. Often it's us."
A growing threat
Research suggests that epidemics of animal diseases and other infectious diseases like Ebola, SARS, avian flu and now Covid-19, caused by a new coronavirus, are on the rise. Pathogens pass from animals to humans, and many of them can quickly spread to new places. The United States Centers for Disease Control and Prevention (CDC) estimates that three-quarters of new or emerging diseases that infect humans come from animals.
Some, like rabies and plague, were transmitted by animals centuries ago. Others, such as Marburg disease, which is said to be transmitted by bats, are still rare. Some, like Covid-19, which appeared last year in Wuhan, China, and the Sea, which is related to camels in the Middle East, are new to humans and are spreading worldwide.
Other diseases that have spread to humans include Lassa fever, first identified in 1969 in Nigeria, Nipah in Malaysia, and Sras in China, which has killed more than 700 people and spread to 30 countries in 2002-2003. . Some, like Zika and West Nile virus, which appeared in Africa, have mutated and established themselves on other continents.
Kate Jones, president of Ecology and Biodiversity at the University of California, calls emerging infectious diseases of animal origin "a growing and major threat to health, safety and the global economy."
In 2008, Professor Jones and a team of researchers identified 335 diseases that appeared between 1960 and 2004, at least 60% of which were caused by animals. According to her, these zoonoses are increasingly linked to environmental changes and human behavior. The disturbance of virgin forests due to logging and mining, road construction in remote areas, rapid urbanization and population growth brings people closer to animal species like never before, she said.
The resulting transmission of disease from wildlife to humans, he says, is now "a hidden cost of human economic development." There are many more of us in all settings. We go to places largely intact and we are increasingly exposed. We create habitats where viruses are more easily transmitted, and then we are surprised to have new ones, "he laments.
Kate Jones is studying how changes in land use are helping to increase this risk. "We are studying how species living in degraded habitats are likely to carry more viruses than can infect humans," he said. "The simplest systems have an amplifying effect. It destroys landscapes, and the species you have left are the ones that infect humans."
"There are countless pathogens that continue to evolve and that, at some point, could pose a threat to humans," says Eric Fevre, chair of the Institute of Infectious Veterinary Infectious Diseases Chair. and Global Health from the University of Liverpool. "The risk of seeing pathogens pass from animals to humans has always been present."
The difference between today and a few decades ago, Fevre says, is that it is likely thatThat diseases develop in urban and natural settings. "We have created dense populations where we have bats and rodents, as well as birds, pets, and other living things. This creates intense interaction and possibilities of passing from one species to another," he observed.
The tip of the iceberg
"Pathogens don't respect the boundaries between species," says environmentalist Thomas Gillespie, an associate professor in the department of environmental science at Emory University, who studies how declining natural habitats and behavioral changes increase risk. spread of animal diseases to humans. "I am not at all surprised by the coronavirus epidemic," he said. "Most pathogens remain to be discovered. We are at the tip of the iceberg".
Humans, Gillespie says, create the conditions for the spread of the disease by reducing the natural barriers between host animals, in which the virus circulates naturally. "We fully expected the arrival of an influenza pandemic; we can expect large-scale human mortality; we can expect other pathogens with other impacts. A disease like the Ebola virus does not spread easily. But an Ebola death rate spread from a disease like measles it would be catastrophic, "Gillespie said.
Thomas Gillespie sees this in the United States, where suburbs fragment forests and increase the risk that humans will contract Lyme disease. "The disruption of the ecosystem affects the complex cycle of the Lyme pathogen. People living nearby are more likely to be bitten by a tick carrying the Lyme bacteria," he says.
According to Kate Jones, change must come from rich and poor societies. The demand for wood, minerals and resources from the global North is generating degraded landscapes and ecological alterations that favor diseases, he said. "We need to think about global biosecurity, find weak points, and strengthen health care delivery in developing countries. Otherwise, we can expect it to be the same," he adds.
"The risks are higher today. They have always been there and have been for generations. Our interactions with this risk are the ones that need to be changed," said Brian Bird, virologist researcher at the University of California, Davis School of Veterinary Medicine One Health Institute , where he directs Ebola surveillance activities in Sierra Leone.
The bottom line, according to Bird, is to be ready. "We cannot predict where the next pandemic will come from, so we need mitigation plans that take into account the worst possible scenarios," he said. "The only thing that is certain is that the next will surely come."