The existence of epidemics and epidemics is nothing new. A review of the history of humanity is sufficient to verify that the people’s fight against infectious diseases has been continuous. Black plague, cholera, tuberculosis, influenza, typhus or smallpox are some examples of diseases that have left us an indelible mark.
Each disease requires specific action and implementation of different prevention, response and treatment mechanisms. For this reason, it is essential to identify the origin and pattern of presence of pathogens.
In this regard, about 60% of emerging infectious diseases reported globally are zoonoses (transmitted between animals and humans). Estimates suggest that around one billion people fall ill and millions die each year as a result of zoonotic events worldwide. And more than 30 new human pathogens have been detected in recent decades, 75% of which originated in animals.
Recent emergence of various zoonotic diseases – avian influenza H5N1, avian influenza H7N9, HIV, Zika, West Nile virus, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), Ebola virus disease or Covid-19 (SARS- CoV2 ) – pose a serious threat to human health and global economic development.
They are usually unpredictable, as many arise in animals and are caused by new viruses that are only detected after an outbreak has occurred. However, there are at least ten factors that we already know with certainty that are associated with the presence of future epidemics or epidemics. We list them.
1. War and Famine
The damage caused by war is many and complex. Death, injury and displacement are the most obvious. But the presence of infectious epidemics is also closely related to armed conflicts.
In 2006, cholera outbreaks were reported in 33 African countries, with 88% of reports coming from countries affected by armed conflict. In recent years, various countries in the Middle East and Africa have suffered infectious outbreaks as a direct effect of war, exacerbated by food and water shortages, displacement, and damage to infrastructure and health services. Is.
2. Land Use Change
Land use change is a human-induced modification of the ecosystem. These changes can affect the abundance and distribution of wildlife, and make it more vulnerable to infection by pathogens. Furthermore, by creating new contact opportunities, they facilitate the movement of pathogens between species, ultimately leading to human infection and further spread of pathogens.
With deforestation and forest fragmentation we favor the extinction of specialist habitat species, allowing generalists to prosper. Wildlife species that are hosts to pathogens, especially bats and other mammalian species such as rodents, have been shown to be relatively more abundant in human-manipulated landscapes, such as agricultural ecosystems and urban areas, than in nearby areas. more than in undisturbed sites.
Establishing pastures, plantations or intensive livestock farms near forest boundaries can also increase the flow of pathogens from wildlife to humans.
4. Uncontrolled urbanization and population growth
Demographic changes in population size and density through urbanization affect the dynamics of infectious diseases. For example, the flu tends to display more frequent outbreaks in more populated and denser urban areas.
5. Climate Change
Climate change increases the risk of viral transmission between species. Many virus species are still unknown, but they are likely to have the potential to infect humans. Fortunately, the vast majority now roam silently in the wild mammals. However, an increase in temperature will cause a mass migration of animals that seek mild environmental conditions, facilitating the appearance of important points of biodiversity. If they reach areas with high human population densities, mainly in Asia and Africa, new opportunities for zoonotic spread among humans will arise.
Recent predictions under climate change scenarios suggest that, by the year 2070, virus transmission between species will increase by about 4,000-fold.
Globalization has facilitated the spread of many infectious agents to all corners of the planet. The transmission of infectious diseases is the best example of the increasing porosity of borders. Globalization and increased connectivity intensify the potential appearance of a pandemic due to the continuous movement of microorganisms through international trade and transport.
7. Hunting, Trade and Consumption of Bushmeat
Zoonotic disease transmission can occur at any point in the bushmeat supply chain, from bushmeat hunting to the point of consumption. Pathogens that can be transmitted from bushmeat to humans are many and include, but are not limited to, HIV, Ebola virus, simian foamy virus or monkeypox virus.
8. Illegal smuggling of species and wild animal markets
A natural ecosystem with a high level of species richness reduces encounter rates between susceptible and infective individuals, reducing the likelihood of pathogen transmission. In contrast, live animal markets and barns dedicated to hiding animals destined for illegal trade are places where all kinds of animal species are caged and overcrowded.
Under these circumstances, not only do they share the same unhealthy and unnatural space, but also ectoparasites and endoparasites which are disease carriers. Animals bleed, salivate, and defecate and urinate on each other, leading to an exchange of pathogenic microorganisms and parasites, leading to intraspecific interactions that should never have occurred.
9. Microbial Growth
Microorganisms are constantly evolving in response to indirect and direct selection pressures in their environment. A clear example is the type A influenza virus, whose ancestral reservoir is waterfowl, from which they have managed to infect other types of animals.
Another clear example of the ability of microorganisms to rapidly adapt is the worldwide evolution of antimicrobial resistance to many types of common human pathogens.
10. Collapse of the Public Health System
In recent decades, in many countries, financial support for public health systems has been gradually withdrawn. This situation has suddenly destroyed the essential and essential infrastructure to deal with the outbreak of the pandemic. The recent rapid emergence of new infectious disease threats such as COVID-19, as well as the resurgence of chronic conditions such as measles or tuberculosis, have important implications for global public health systems.
We should be aware that there is a need to conduct a thorough and in-depth study of the potential factors that facilitate the emergence of infectious diseases in order to prepare against possible future epidemics and epidemics. Calm and critical analysis will allow future prediction and prevention strategies to be designed.
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