Ten circumstances that lead us to a new pandemic

Epidemics and pandemics are nothing new. A review of the history of humanity is enough to see that the struggle of people against infectious diseases has been constant. The Black Death, cholera, tuberculosis, influenza, typhus or smallpox are just some examples of diseases that have left us with indelible scars.
Each disease requires specific action and the implementation of different prevention, response and treatment mechanisms. For this reason, it is essential to identify the origins and patterns of appearance of pathogens.
In this sense, about 60% of the emerging infectious diseases reported globally are zoonoses (which are transmitted between animals and humans). Estimates suggest that, worldwide, every year, around one billion people get sick and millions die as a result of zoonotic events. And of the more than 30 new human pathogens detected in recent decades, 75% have originated in animals.
The recent emergence of various diseases of zoonotic origin – H5N1 avian influenza, H7N9 avian influenza, HIV, Zika, West Nile virus, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), Ebola virus disease or COVID-19 (SARS-CoV2) – have posed serious threats to human health and global economic development.
In general, they are unpredictable, since many originate in animals and are caused by new viruses that are only detected once an outbreak has occurred. However, there are at least ten factors that we already know for sure that are linked to the emergence of a future epidemic or pandemic. We list them.
1. Wars and famines
The damage caused by war is many and complex. Death, injury and displacement are the most obvious. But the emergence of infectious epidemics is also closely related to war.
In 2006, cholera outbreaks were reported in 33 African countries, and in 88% of cases the reports came from countries affected by war. In recent years, different countries in the Middle East and Africa have suffered infectious outbreaks as a direct effect of war, aggravated by food and water shortages, displacement and damage to infrastructure and health services.
2. Land use change
Land use change is a human-induced modification in the ecosystem. These alterations can affect the abundance and distribution of wildlife, and make it more susceptible to infection by pathogens. In addition, by creating new contact opportunities, they facilitate the circulation of pathogens between species, ultimately leading to human infection and further spread of pathogens.
3. Deforestation
With deforestation and the fragmentation of forests we favor the extinction of species specialized in habitats, allowing generalists to thrive. Wildlife species that host pathogens, particularly bats and other mammal species such as rodents, have been found to be relatively more abundant in human-manipulated landscapes, such as agricultural ecosystems and urban areas, than in adjacent undisturbed sites.
Establishing pastures, plantations, or intensive cattle ranching farms near forest margins can also increase the flow of pathogens from wildlife to humans.
Deforested area of the Brazilian Amazon.
Shutterstock / Tarcisio Schnaider
4. Uncontrolled urbanization and population increase
Demographic changes in population size and density through urbanization affect the dynamics of infectious diseases. For example, influenza tends to exhibit more persistent outbreaks in more populated and dense urban regions.
5. Climate change
Climate change increases the risk of viral transmission between species. Many species of viruses are still unknown, but they likely have the ability to infect humans. Fortunately, today the vast majority circulate silently in wild mammals. However, rising temperatures will cause mass migrations of animals seeking milder environmental conditions, facilitating the emergence of biodiversity hotspots. If they reach areas of high human population density, mainlyIn Asia and Africa, new opportunities will arise for zoonotic spread to humans.
Recent predictions under climate change scenarios suggest that, by 2070, virus transmission between species will increase by about 4,000 times.
6. Globalization
Globalization has facilitated the spread of numerous infectious agents to all corners of the planet. The transmission of infectious diseases is the best example of the growing porosity of borders. Globalization and increased connectivity accelerate the possible emergence of a pandemic due to the constant mobilization of microorganisms through international trade and transport.
7. Hunting, trade and consumption of bushmeat
Transmission of zoonotic diseases can occur at any point in the bushmeat supply chain, from hunting in the forest to the point of consumption. Pathogens that have spread to humans from bushmeat are numerous and include hiv, Ebola virus, ape foam virus or monkeypox virus.
Appearance of the Market of Tomohon, in Indonesia, where wild animals are traded for consumption.
Shutterstock / Sony Herdiana
8. Illegal trafficking in wild animal species and markets
A natural ecosystem with a high degree of species richness reduces the rate of encounter between susceptible and infectious individuals, decreasing the probability of transmission of a pathogen. By contrast, live animal markets and enclosures dedicated to hiding animals intended for illegal trade are places where animal species of all kinds are caged and overcrowded.
In these circumstances they not only share the same unhealthy and unnatural space, but also ectoparasites and endoparasites vectors of diseases. Animals bleed, drool, and defecate and urinate on each other, leading to the exchange of pathogenic microorganisms and parasites, forcing interactions between species that should never occur.
9. Microbial evolution
Microorganisms are constantly evolving in response to indirect and direct selection pressures in their environment. A clear example is influenza A viruses, whose ancestral reservoir is waterfowl, from which they have managed to infect other types of animals.
Another glaring example of the ability of microorganisms to adapt quickly is the global development of many types of antimicrobial resistance in common human pathogens.
10. Collapse of the public health system
In recent decades, in many countries, there has been a gradual withdrawal of financial support for public health systems. This situation has decimated the essential and necessary infrastructure to deal with shocking outbreaks. The recent rapid emergence of new infectious disease threats such as COVID-19, coupled with the resurgence of old conditions such as measles or tuberculosis, has important implications for global public health systems.
We must be aware that preparedness against possible future epidemics and pandemics requires a thorough and thorough study of the potential factors that facilitate the emergence of infectious diseases. The calm and critical analysis will allow the design of future forecasting and prevention strategies.
Raúl Rivas González, Professor of Microbiology, University of Salamanca
This article was originally published on The Conversation. Read the original.

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