One health, one world

The world is facing an unprecedented health crisis caused by infectious diseases. According to the US National Institute of Health, 60% of all infectious diseases in humans are of animal origin (zoonotic), and they represent 75% of new and emerging diseases.

Among the most well-known zoonotic diseases that affect the human population are bird flu, rabies, and brucellosis, which continue to pose significant public health risk.  Other diseases, primarily transmitted person-to-person, but with animal reservoirs, can cause serious health crises. They include Ebola and several coronavirus, severe acute respiratory syndrome (SARS) detected in 2003, Middle East Respiratory Syndrome (MERS) detected in 2012, and the current COVID-19 pandemic caused by the new coronavirus (SARS-CoV-2). Although the mechanism that introduced COVID-19 remains identified, the World Organization for Animal Health (OIE) indicates that an interaction at a specific moment enabled the pathogens transmission between species.

Environmental factors and disease transmission

There is a direct relationship between the transfer of pathogenic agents from wild animals to human, and environmental factors such biodiversity loss, exponential human population growth, the introduction of invasive species, intensive agricultural practices, and deforestation. Although those processes are not fully understood, the degradation of natural habitats represents a direct threat for many species, even the exact impact of these alterations on disease transmission and susceptibility remains unclear.

An illustrative example is the appearance of the Nipah virus in the late 1990s in domesticated pigs of Malaysia and Singapore. This virus has a natural reservoir host in fruit bats, also known as “flying foxes.” Massive deforestation programs in the region, the location of pig farms, and the cultivation of fruit trees near these farms created the perfect storm. Bats from tropical forests changed their habitat due to deforestation and began to approach the fruit trees adjacent to the farms, exposing the pigs to their contagious urine and fecal material. Consequently, the transmission to humans was through direct contact with the excretions and secretions of the infected pigs.  

Economic impact of zoonotic diseases

In 2016, the United Nations Environment Programme (UNEP) published its Frontiers Report on emerging environmental concerns. The report noted that, in the last two decades, zoonotic diseases have caused direct costs of more than $100 billion, and that the losses would have been in the trillions if those outbreaks had become human pandemics. These effects would be mitigated if development projects applied safeguards and conducted social and environmental analyses, considering the effect of the cumulative impact on natural resources and on  biodiversity, rather than only the effect of each individual project.

In the case of COVID-19, governments acted urgently, establishing containment measures to prevent the spread of the virus. Respect for the environment is not exempt from the urgency of the measures, as it ensures food security and the idiosyncrasies of each community. Environmental and social legislation and safeguard policies can guide governments on how to protect the environment and society in those difficult times.

However, prevention, control, and vigilance at the source are indispensable as the most economical and efficient solutions to protect public health, and prevent such pathogens from colonizing new territories and evolving into new forms. The first step to reducing the risks of these diseases is to understand them. This requires collecting relevant data and sharing information among experts in all the disciplines and sectors involved in this health problem. 

One Health

Currently, there is a global strategy established under the framework “One Health,” a concept introduced in 2000 that involves a paradigm shift. It recognizes that human health and animal health are interdependent and linked to their ecosystems.

The concept has an intersectoral and multidisciplinary focus that helps us understand how animals, humans, and the environment interact, and how those interactions affect the emergence of infectious diseases.  “One Health” has been recognized by major governmental and non-governmental organizations involved in health and development globally as a key strategy for disease control and prevention.  

Where do we start?

Technological advances have generated a large quantity of data that provides key information for the evaluation and mitigation of social and environmental risks. Risk analysis depends on factors such as the available information, the urgency of the evaluation, and the complexity of the questions to be assessed. Analyzing these data can shed light on human behavior in a given situation and, in turn, on the behavior of the infectious agents, including common routes for contagion or cultural habits that facilitate contagion. Additionally, applying environmental and social safeguards adds another layer of protection to prevent permanent damage, ensuring the health of ecosystemic, humans, and animals.

Employing real-time data sources, such as social networks, combined with environmental and social information (i.e. historical data and satellite tracking), can enable the creation of heat maps or risk dynamics mapping of infectious diseases. This allows for early warnings and situational analyses based on location. Scientists have the tools to conduct in-depth research on the possible relationship between those factors. This research will be key for predicting and preventing outbreaks that can affect domestic and wild animals, as well as humans, worldwide.

Unfortunately, the knowledge about the global distribution of most infectious diseases is extremely limited. This lack of geographic knowledge frustrates various clinical, epidemiological, and public health studies. While epidemiological work was always necessary, its importance is accentuated in the prevailing context of COVID-19.

Credit for bats photo: Flicker