These ten risks that can lead to a pandemic – Evening edition Ouest-France

By Raúl Rivas González, Professor of Microbiology at the University of Salamanca

While pandemics are unpredictable, there are at least ten man-made risks that can cause a global epidemic to recur, according to Raúl Rivas González, professor of microbiology at the University of Salamanca, Spain. Explanations.

Epidemics and pandemics are, unfortunately, nothing new. A simple glance at the history of mankind is enough to show that the fight of our species against infectious diseases has been constant. Not to mention the recent Covid-19, the Black Death, cholera, tuberculosis, influenza, typhoid or smallpox are just a few examples of those that have left indelible traces…

Each disease requires specific action and the implementation of different prevention, response and treatment mechanisms. This is why it is essential to identify the origins and modes of appearance of pathogenic agents.

In this regard, approximately 60% of emerging infectious diseases reported worldwide are zoonoses (which are transmitted between animals and humans). It is estimated that approximately one billion people worldwide become ill and millions die each year as a result of zoonotic events. And of more than 30 new human pathogens detected in recent decades, 75% originated in animals.

The recent emergence of several zoonoses – avian influenza H5N1, avian influenza H7N9, HIV, Zika, West Nile virus, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), Ebola or Covid-19 (SARS -CoV-2) among others – has posed serious threats to human health and global economic development.

They are generally unpredictable, as many originate in animals and are caused by new viruses that are only detected after the fact. However, there are at least ten factors that we already know for sure are linked to the emergence of a future epidemic or pandemic. They are gathered together and explained below.

1. Wars and famines

The damage suffered by war is obviously numerous and complex: the deaths, injuries and massive displacements of populations to flee the fighting are the most obvious. But the emergence of infectious epidemics is also linked to conflicts.

In 2006, cholera outbreaks were reported in 33 African countries, 88% of them in conflict-affected countries. In recent years, several countries in the Middle East and Africa have experienced infectious epidemics as a direct consequence of war, exacerbated by food and water shortages, displacement and damage to infrastructure and health services.

2. Land use change

Land use change is a major modification of the ecosystem induced directly by human populations. The consequences are very great.

These alterations can indeed affect the diversity, abundance and distribution of wild animals and make them more susceptible to infection by pathogens. Furthermore, by providing new opportunities for contact, they drive the circulation and spread of pathogens between species, which can ultimately lead to human infection.

3. Deforestation

Through deforestation and forest fragmentation, we promote the extinction of specialist species in these habitats and the development and installation of more generalist species. Some wildlife species that are hosts to pathogens, particularly bats and other mammalian species such as rodents, are relatively more abundant in landscapes so transformed, such as agricultural ecosystems and urban areas, than in adjacent undisturbed sites.

The establishment of pastures, plantations or intensive livestock operations near forest edges can also increase the flow of pathogens from wildlife to humans.

Deforested area of ​​the Brazilian Amazon. (Photo: Tarcisio Schnaider/Shutterstock)

4. Uncontrolled urbanization and population growth

Changes in population size and density due to urbanization again affect the dynamics of infectious diseases. For example, influenza tends to have more persistent epidemics in more populated and dense urban areas.

5. Climate change

Climate change increases the risk of cross-species viral transmission. Many virus species are still unknown, but are likely to have the ability to infect our species. Fortunately, the vast majority of them currently circulate silently among wild mammals.

However, the expected rise in temperatures with climate change will lead to massive migrations of animals in search of milder environmental conditions, which will facilitate the emergence of “biodiversity hotspots” (threatened biogeographical area with at least 1,500 species endemic plants and animals). If they reduce areas of high human population density, primarily in Asia and Africa, new opportunities for zoonotic spread to humans will arise.

According to recent findings based on climate change scenarios, by 2070 virus transmission between species will increase approximately 4,000 times.

6. Globalization

Globalization facilitates the spread of many infectious agents to all corners of the world.

The transmission of infectious diseases is the best example of the growing porosity of borders. Globalization and connectivity accelerate the potential emergence of a pandemic, and its rapid spread, due to the constant movement of microorganisms through international trade and transport.

7. Bushmeat hunting, trade and consumption

Transmission of zoonoses can occur at any point in the bushmeat supply chain, from hunting in the forest to the place of consumption. Pathogens that have been transmitted to humans from bushmeat are numerous and include but are not limited to HIV, Ebola virus, simian foamy virus and monkeypox virus…

A view of the Tomohon market in Indonesia, where wild animals are traded for consumption. (Picture: Sony Herdiana/Shutterstock)

8. Illegal cash trafficking and wildlife markets

An ecosystem with high species richness reduces the encounter rate between susceptible and infectious individuals, which decreases the likelihood of pathogen transmission. Conversely, live animal markets and other hidden illegal trade enclosures are places where the most diverse species are crammed into overcrowded cages.

Under these conditions, not only do they share the same unhealthy and unnatural space, but also disease-carrying ectoparasites and endoparasites. Animals bleed, drool, defecate and urinate on each other: this leads to the exchange of pathogenic microorganisms and parasites, thus forcing interactions between species that should never have happened.

9. Microbial evolution

Microorganisms are constantly evolving, naturally and in response to direct and indirect selection pressures from their environment. A well-established example is that of the influenza A viruses, whose ancestral reservoir is waterfowl, from which they succeeded in infecting other types of animals.

The worldwide development of many types of antimicrobial resistance in common human pathogens is a clear demonstration of the enormous capacity of microorganisms to adapt rapidly.

10. Collapse of public health systems

Over the past decades, in many countries, on assistance to a gradual withdrawal of financial support to public health systems.

This decimated the critical infrastructure needed to deal with sudden outbreaks. The recent and rapid emergence of new infectious disease threats, such as Covid-19, coupled with the resurgence of older diseases, such as measles and tuberculosis, has important implications for global public health systems.

We should be aware that preparing for possible future epidemics and pandemics requires careful and conscious study of potential factors that modify the emergence of infectious diseases. A delicate and critical analysis will make it possible to define future forecasting and prevention strategies.

The original version of this article was published in The conversation.

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