From living things destruction to the emergence of infectious diseases : the question of viruses

 

While the link is easily established between the exploitation of natural resources and the destruction of living things. It is less, about the relationship between globalization, climate change and the emergence of infectious diseases.

Infectious diseases are caused by the transmission of a pathogenic micro-organism: viruses, bacteria, parasites, fungi and protozoa. Unlike bacteria, viruses require a living host to multiply and transmit their genetic material. Bacteria, on the other hand, can multiply on inert surfaces such as door handles, toilet bowls or telephones. However, and as the Covid-19 crisis illustrated, this does not mean that viruses die instantly outside a living host.

 

When a virus invades your body, the cells covered with receptors envelop and absorb the virus, this is the phenomenon of endocytosis. The virus then transmits its genetic material through membrane receptors (located on the virus envelope) and forces the cell to replicate it within the host cells. In addition, viruses are frequently contagious and are transmitted by different routes, such as: blood, saliva and droplets. The measles or flu virus is a good illustration of this problem and explains the epidemics they cause.

 

But what is the relationship between the destruction of life and the emergence of these viral infectious diseases?

 

According to experts in the field, the majority of zoonoses (diseases that are transmitted between humans and other animals) originate in wildlife. Bats are often “reservoir species,” partly because they carry many bacteria and viruses and live in colonies, which facilitates transmission. Ebola and Nipah viruses, but also some coronaviruses are known to be carried and transmitted by bats. In addition, they can also be transmitted by farm animals.

Firstly, it is  the proximity of humans to wild or domestic animals that multiplies exposure to pathogens. Meanwhile, these are infectious agents whose genetic material is found in nature. While, on the other hand, it is the promiscuity, sometimes deplorable hygiene and lack of genetic diversity of intensive livestock farming that make them real cauldrons for pathogens (swine and bird flu, mad cow disease, etc.). Today, according to the WHO, 75% of emerging infectious diseases are zoonoses and represent 2.5 billion cases each year.

The health of non-human animals and humans are linked and there is a clear relation between the emergence of pandemics and the intensification of goods and people flows, which has led to the internationalisation of nearly all regions of the world. Mobility therefore makes us more vulnerable, just as much as overpopulation. This is what an article written by IPBES guest experts says:

 

“Only one species is responsible for the COVID-19 pandemic: we as human beings. As with the climate and biodiversity crises, recent pandemics are a direct consequence of human activity … Unrestrained deforestation, uncontrolled expansion of agriculture, mining and infrastructure development, and wildlife exploitation have created the “perfect conditions” for the spread of diseases transmissible from wildlife to humans. »

Pandemics are therefore caused by activities that bring an increasing number of people into direct and often conflicting contact with animals carrying these pathogens. As the latest IPBES report reminds us, our activities have an increasing negative impact on nature: 85% of wetlands have disappeared since the 16th century and 75% of the land surface is significantly altered by human activities. In 40 years, we have lost 60% of wild animals and the report estimates that one million animal and plant species are now threatened with extinction.

 

If we combine this reality with the unregulated trade in wildlife and the explosion of global air travel, we can see how a virus that once circulated harmlessly among one species in Southeast Asia has been able to spread to dozens of countries and affect several million people. The potential for virus transmission is not to be outdone since a well-known animal plays a central role in this “virologic equation”: the mosquito.

 

Mosquitos, 400 million years old, have been living with Eurasian populations since the Neolithic revolution. In 1492, they embarked with Christopher Columbus and brought malaria to the Americas. The Slave Trade also enabled them to spread to Florida, Central America, present-day Colombia and southern Brazil. Their capacity to transmit diseases makes them the deadliest species for humanity, several million people annually. Two species are catching health authority’s attention: Anopheles, vectors of malaria (for which there is no vaccine) and Aedes, that transmit the dreaded viruses called Arboviruses (Chikungunya, Dengue fever, Yellow Fever, Zika and Nile Fever).

 

While exploration was the beginning of the redistribution of mosquitoes around the world, global warming and globalized trade are expanding their presence around the world. Moreover, mosquitoes are among the most widespread animals on Earth, along with humans. As an example, the Aedes albopictus or tiger mosquito will travel by container, following maritime transport routes, from the end of the 20th century. Hence, according to the United Nations Conference on Trade and Development, about 80% of world trade by volume and more than 70% of world trade by value is carried by the seas[1].

 

As you will have understood, if the climate has a notable importance in the face of all these diseases. For now on, it is our activities that play a more direct and major role. Thus, it is indeed in a context of “total liberalization of trade” (to use Maurice Allais’ words) that this pandemic has emerged, notwithstanding those who observe no connection with the way we live in space and exploit natural resources.

 

[1] DEVPORT 2020 : Ports, transport maritime et développement régional : Globalisation, jeux d’échelles et environnements, available online : https://devport2020.sciencesconf.org/resource/page/id/1 .

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Sources :

  • http://ipsnews.net/francais/2020/04/27/les-mesures-de-stimulation-liees-au-covid-19-doivent-sauver-des-vies-proteger-les-moyens-de-subsistance-et-sauvegarder-la-nature-pour-reduire-le-risque-de-futures-pandemies/
  • https://www.persee.fr/doc/globe_0398-3412_1979_num_119_1_1123
  • https://www.who.int/neglected_diseases/vector_ecology/mosquito-borne-diseases/en/

A propos de Albéric BARRET

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