More than two years after the Covid pandemic began, science has still not been able to determine which animal this coronavirus came from. It is certain, however, that global warming will increase the risk of more of these viral exchanges between species.
The closest relatives of the Sars-CoV-2 virus were found in bats in China, where the first cases of the disease also emerged. It is likely that a mutated strain has spilled over from one of these flying critters to another mammal or bird and, from this unidentified vector, to humans.
The jump between animal species is at the origin of diseases called zoonoses. With climate change underway, rising temperatures force many of these organisms to migrate to cooler areas, where they will come into contact with members of species already living there.
When animals meet, attack or eat each other, they exchange viruses, which may or may not be able to infect the new species. Some will be, and one of those species could be the human.
It is estimated that there are 10,000 viruses competent to invade human cells. Most of them are still silently waiting in other mammals for the opportunity to jump on us. Under normal conditions, this is rare.
A scientific paper published online ten days ago in the journal Nature estimated the likelihood of such pernicious encounters happening over the next half century as the climate crisis inevitably worsens. There is nothing reassuring about the study.
Researchers from the US and South Africa created computer models fed regional predictions of temperature rise, species distribution, and possible escape routes (usually to higher, cooler locations). They concluded that 3,139 species of mammals will change area by the year 2070.
The authors estimate that, amid the flurry, viral spillover events could double the number and hit 4,000 in the next five decades. Worse, even if we manage to keep the warming of the atmosphere below 2°C, a goal that is not feasible at the current pace of decarbonization of the economy, the leaps will happen anyway.
Dispersion, however, occurs slowly in most species, which encounter physical and ecological barriers along the way. But there is one mammal that can go further and faster — bats, because they fly.
The regions at greatest risk are in Asia and Africa, especially India, Indonesia and the Sahel (African region sub-Saharan). Several conditions would contribute to this: high heat, high concentration of biodiversity and human beings.
It may seem reassuring to Brazilians that the Amazon does not appear in the survey as a high-risk sector, despite the biodiversity and human advance on the forest. Due to its immensity, high endemism and low average altitude, species harassed by climate change have nowhere to flee.
However, as Covid made clear, it only takes a few months for a pandemic to spread across the globe and get here. Viruses travel by plane. And the damage they do or fail to do depends on the quality of the government and health surveillance in the invaded territory (and everyone saw the damage done by Jair Bolsonaro here).
All that remains is prevention, with zoonotic and genetic surveillance, to identify an overflow or the arrival of new viruses in the country early. Brazil should create an agency just for that, in the style of the US Centers for Disease Control (CDC), as proposed by Gonzalo Vecina Neto and Pedro Barbosa, in Sheeton the 24th of April.
Suggestion: from the Fiocruz structure, which is already present in ten states and has competence in the field, to create the CDC of the B.B of Brazil, of the Brazilian State, not of Bolsonaro.
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