Over the past two years, words like zoonosis (a disease that is transmitted from animals to humans) and spillover (the “leap of species”) have entered our daily vocabulary. Will it still be like this in twenty years? Is the pandemic we are experiencing destined to remain an isolated parenthesis in our history, or is it the beginning of a cycle ?

At a time when the media attention is monopolized by vaccines , we preferred to go against the tide and ask ourselves a few more profound questions about why Covid-19 . Accompanying us is Danilo Russo , professor of Ecology at the Department of Agriculture of the Federico II University of Naples.

What are the similarities between coronavirus and other zoonoses?

This zoonosis, like many others, is the daughter of a bad relationship between man and nature . Unfortunately we do not know the exact causes of this umpteenth zoonotic event but we do know that, most likely, it is linked to the consumption of wildlife ( bushmeat ) in many regions of the world. In this case it took place in China , but there are many other places in the world where animals are caught to consume them for food, therapeutic purposes and so on. 

It is a large phenomenon that was once limited to the sustenance of small groups but then, with the advancement of urbanization and the increase in population, it has reached unsustainable dimensions . Unsustainable not only in terms of conservation of species – which are taken from nature and often reduced to a flicker – but also, as we have seen, in terms of zoonotic risk .

What certainties do we have about the origin of the coronavirus?

We do not know which animal species this virus comes from. We slammed bats on the front page because some coronaviruses, genetically similar to this one, are present in some bat species living in southern China. However, we absolutely do not know which host was from which – directly or indirectly – this virus came. It has also been speculated that it passed through intermediate species to reach humans. Frankly, I think this topic distracts attention from the fundamental reason , which is the unnatural contact with wildlife. 

What are the conditions that facilitate the “species leap” of the virus from animals to humans?

The truth is, we have a wildlife consumption problem in many parts of the world, including China. This implies a number of things. Animals are captured in their natural environment and transported under hallucinating conditions . When they arrive at the markets they are already immunosuppressed and are all kept together, creating a cocktail of species that in nature would not come into contact with each other. They are often slaughtered in situ and therefore retailers and buyers are in contact not only with live animals but also with their blood. This creates a “ perfect storm ”, the ideal environmental condition for onespillover , i.e. the passage of a pathogen from one species to another.

When the spillover is about humans, the virus has won the lottery. We are the ideal species for a zoonotic event because we are many, we live in close proximity, we are highly social and we move very quickly from one part of the globe to another. We take airplanes, which other species do not; even the best of migrants would take months to travel the routes we cover in the space of a few hours. That is the ideal condition for a virus to thrive.

There is one thing that needs to be highlighted. One thing is the evolutionary origin of the virus, that is the species from which it comes. Another is the epidemiological origin , linked to the environmental context and human actions. I have talked about bushmeat and the consumption of wildlife, but this is only one of many aspects that are difficult to separate from each other: deforestation , the fragmentation of forest environments, the expansion of agriculture and urban areas within regions an uncontaminated time … All these phenomena create new frontiers of contact between man and wildlife , determining unnatural conditions of proximity that can give rise to zoonotic events. THEclimate change increases this risk. 

So this pandemic will not remain an isolated case?

The overall environmental picture makes zoonoses more frequent. There has already been an exponential increase in the last fifty years and now we will have to wait for the next ones. The question is not “if” we will have a next pandemic but “when” , because all the factors I have just described are absolutely out of control and are increasingly impacting.

So you are saying that we have found a vaccine, but we have not found – or we have not wanted to find – a method to intervene in a structural way on the causes …

Absolutely. The vaccine is a corrective strategy, not a preventive strategy . Or rather, it prevents the risk of getting infected, not the risk of a new pandemic taking place. Only by intervening on environmental causes is it possible to prevent further pandemic events, but we are not doing it . As long as we continue to go forward with business as usual , as long as we do not become aware of what are the factors behind zoonotic events, the risk will be stronger and stronger . Also because the global population continues to grow, we are almost eight billion.

So far we have talked about wild animals, but what role do intensive farming play?

Farms often occupy natural environments and, consequently, create contact between wild and domestic . When the pathogen passes into pets and the latter are housed with unnatural densities, there is a great risk of transmission. Pets are very powerful amplifiers . If the virus enters pigs, for example, the viral load increases. We are always in close proximity to pets ; if these come into contact with a virus from wild animals, they can carry it to humans in an extremely efficient way.

So it would be a question of rethinking the food system as a whole …

Of course. Minks ,  for example, have been affected by Covid-19 , in Denmark and also in Italy. In all likelihood, the virus came from the people who ran these farms and was given the green light, considering that the animals were packed beyond belief and therefore immunosuppressed . Millions of animals had to be killed to contain the infection; it seems they have made it, but it is a good example of how much intensive farming is part of this problem. The difficult thing to make people understand is that we are facing an environmental crisis , even before a health crisis. It is one of the lights that have lit up on the dashboard of the Planet to indicate that something is now really going wrong.