Future Coronaviruses could originate from the oceans

New marine Coronaviruses could appear tomorrow -

• The reduction of the borders between wild life and human activities would favor the transmission of new viruses, according to a study published by our partner The Conversation.

• Still poorly understood, viruses, bacteria and protozoa represent about 60% of the biomass of the oceans.

• The analysis of this situation was carried out by Timothée Ourbak, climate change expert with the French Development Agency (AFD).

SARS-CoV-2 appeared in China at the end of 2019. This coronavirus would have probably been transmitted to humans in China by an intermediate animal, itself infected by a bat, without this animal or for the time being clearly identified.

Epidemics or pandemics are natural processes, which human societies have been confronted with on numerous occasions in the past, let us quote, recently, the case of the Ebola virus disease which started in Guinea.

Despite this, “renowned scientists also said that the Covid-19 crisis was a clear warning message, as many other deadly viruses exist in wild life and our current civilization is playing with it. fire, ”notes the Director General of the United Nations Environment Program.

Indeed, many scientists defend the existence of a correlation link between the reduction of the borders between wild life and human activities, and the transmission of new viruses potentially fatal to humans.

This transmission is facilitated for pathogens which pass from wildlife and domestic animals to people.

This is the case for the terrestrial world, but what about the marine world?

Human activities responsible for the spread of germs and disease

The destruction of natural spaces can reasonably be regarded as one of the determining causes of the development of epidemics, because it makes possible contacts between humans and species carrying these infectious pathogens.

This phenomenon is called the “crossing of the species barrier”.

Viruses, due to the frequency of contact with human organisms, eventually adapt and evolve, thus becoming pathogenic.

Under these conditions, human activities are directly responsible, not for the appearance, but for the spread of these diseases.

This is explained by the latest report from the intergovernmental platform for biodiversity and ecosystem services, IPBES: human pressures weaken the “natural” barriers existing between different ecosystems.

The link between damage to biodiversity and human health has been observed during the last epidemic crises, and projections by the Intergovernmental Panel on Climate Change (IPCC) have also pointed to the risk of aggravation by climate change: these endanger the survival of many ecosystems and promote the proliferation of microbial species.

A crazy diversity of microbes in the ocean

While the link between climate change and the appearance or spread of pathogens has been studied for terrestrial life, studies concerning marine life remain few, even though the oceans represent nearly 70% of the earth's surface and nine tenths of the earth. habitable volume for the living.

Climate change will affect the oceans, but we do not yet fully understand the consequences on microbial populations.

In 2005, “only” 200,000 marine species of microbes had been described.

The oceans are home to very diverse communities geographically.

For example, a recent inventory of viruses and other marine species showed that there is an important viral reservoir at the level of the North Pole, with no less than 167,526 different populations, against 11,053 in Antarctica.

But if they represent around 60% of the biomass of the oceans, the viruses, bacteria and protozoa living in the ocean environment are still unknown.

What will be the effects of climate change on marine microbes?

Microbial diversity in the oceans plays an important ecological role.

For example, marine microorganisms - viruses, archaea, bacteria, protists, microalgae - are involved in the fixation of CO2, the production of oxygen, the fixation of ammonia and nitrogen, the use of nitrates and sulfates, and metal metabolism in the absence of oxygen.

Despite these decisive roles, our knowledge of the impact that climate change will have on these populations remains limited, for example, the consequences of ocean acidification on viruses.

While we know that warming oceans are expected to encourage the multiplication of microbes and accelerate their growth, the proportions in which this is expected to occur remains to be determined.

Although difficult to assess, one of the expected transformations is in the melting of polar ice and more generally of permafrost.

For example, IPCC experts believe that the emergence of diseases, such as those affecting ungulates and attributed to nematodes, will be favored;

and this despite the uncertainty that still surrounds the magnitude of the consequences of climate change.

In addition, the arrival of new species risks upsetting the existing balances: corals, for example, are already in competition with new non-coral species - a phenomenon which could also occur at the level of the poles.

Insofar as biodiversity plays a key role in the functioning of ecosystems, these upheavals could worsen the consequences of climate change.

Human communities dependent on ocean life

In addition, many human communities depend on the maritime space, especially the coastal area.

These will necessarily be the first to be impacted by these transformations: the appearance of a disease that threatens fish stocks could cause a food and health disaster.

This risk is all the more increased as aquaculture promotes the development of microbes which can subsequently contaminate wild species.

One of the most significant recent examples is undoubtedly the spread of the AIS virus (infectious salmon anemia), which appeared in Chile in 2007, at the origin of several major epidemic episodes.

Although this virus is not zoonotic (i.e. which can be transmitted from animals to humans or vice versa), it has nevertheless endangered the economy of the sector, its populations as well as the biodiversity of the region.

In addition, there is the added risk of seeing old viruses eradicated or new potentially dangerous viruses being released from the melting ice.

The melting of permafrost could thus see the reappearance of eradicated viruses such as smallpox.

What is the risk of transmission of a marine virus to humans?

This risk appears, at least for the moment, to be quite low since no zoonotic marine virus has been discovered so far.

Indeed, of the 129 species of viruses involved in human diseases, all are of terrestrial origin.

This is also the case for the 1,415 infectious organisms that can be pathogenic for humans, 61% of which are zoonotic.

If transmissions between animals and humans are possible on land, reasoning by direct analogy for marine viruses shows its limits.

In addition to the risks of inter-species transmission and the risks of zoonotic transmission to humans, it is the good health of ecosystems that is at stake, and therefore that of the women and men who depend on them.

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This analysis was written by Timothée Ourbak, climate change expert at the French Development Agency (AFD)

• epidemic

• Global warming

• Coronavirus

• Ocean

• Science