The world is facing an unprecedented health crisis caused by infectious diseases. According to data provided by the World Health Organization (WHO), it is estimated that 60% of all infectious diseases registered in humans are of animal origin (zoonotic) and 75% of new or emerging ones are zoonotic.
Avian influenza, rabies, or brucellosis stand out as the best-known examples of zoonotic diseases that affect the human population, and they continue to pose a very high risk to public health. Other diseases transmitted essentially from person to person maintain reservoirs in animals and can cause serious health crises. Examples include the Ebola virus and, the Severe Acute Respiratory Syndrome (SARS) detected in 2003, the 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 of introduction of Covid-19 has not yet been identified, the World Organization for Animal Health (OIE) indicates that “at some point” an interaction took place that allowed the transmission of the pathogen between different species.
In this sense, there is a direct relationship between the transfer of pathogens from wild animals to humans and environmental factors, such as the loss of biodiversity, the exponential growth of the human population, the wild animal trade, the introduction of invasive species, intensive agricultural practices, or deforestation. Although these processes are still unknown, there is no doubt that the degradation of natural habitats represents a direct threat to many species, although it is not yet clear how these alterations affect the transmission and susceptibility of the disease.
An illustrative example is new emergence in the late 1990s of the Nipah virus, a zoonotic infectious disease in domestic pigs in Malaysia and Singapore. Its natural reservoir are fruit bats, also known as “flying foxes”. The massive deforestation programs in the region, the location of pig farms, and the fruit orchards near these farms created the perfect storm. Tropical forest bats changed habitats due to deforestation and approached the fruit trees by the farms, exposing domestic pigs to their contagious urine and fecal matter. In turn, transmission to humans resulted from direct contact with the excretions and secretions of infected pigs.
In 2016, the United Nations Environment Program (UNEP) published its Frontiers Report on Emerging Issues of Environmental Concern. It reflected that in the last two decades zoonotic diseases have caused direct costs of more than 100 billion dollars and that the losses would have been several trillion if these outbreaks had turned into human pandemics. These effects would be less if safeguards and socio-environmental analyzes considered cumulative impacts on natural resources and biodiversity had been applied in development projects, and not only the impacts of each project individually.
In the case of Covid-19, governments have acted urgently, establishing containment measures to prevent the spread of the virus. The urgency of the measures does not exempt them from respecting the environment in a way that ensures food safety and the idiosyncrasy of communities. Environmental and social legislation and safeguards policies can guide governments on how to ensure the protection of the environment and society in these difficult times.
Therefore, prevention, control, and surveillance at the source are the most economical and effective solutions to protect public health and to prevent pathogens from colonizing new territories and evolving in new ways. The first step in reducing the risks of these diseases is to understand them. This requires collecting relevant data and sharing expert information in all the disciplines and sectors involved in this health issue.
Currently, there is a global strategy established within the framework of “One Health”, a concept introduced in 2000, which implies a paradigm shift and determines that human health and animal health are interdependent and linked to their ecosystems.
This concept has an intersectoral and multidisciplinary approach that helps to understand how animals, humans, and the environment interact, and how those interactions affect the appearance of infectious diseases. ’One Health’ has been recognized as one of the main disease control and prevention strategies by the world’s leading governmental and non-governmental health and development organizations.
Where do we start?
Technological advances are associated with a large amount of data that provides key information for the evaluation and mitigation of environmental and social risks. The analysis of risks depends on factors such as the information available, the speed with which the evaluation is required, and the complexity of the questions to be evaluated. Analyzing these data can shed light on human behavior in a situation and, therefore, on the behavior of infectious agents: most common contagion routes, proliferation speed, most vulnerable population, or cultural habits that open doors to contagion. In addition, the application of environmental and social safeguards adds another layer of protection to prevent damage from being permanent, ensuring the protection of ecosystem, human, and animal health.
Using real-time data sources, such as social networks, combined with other sources of environmental and social information, such as historical data or satellite tracking, can provide dynamic maps of infectious disease risks helping indicate where to activate alerts and prioritizing the situation by location. Scientists have tools to further investigate the possible relationship between these factors. This research will be imperative to help predict and prevent outbreaks that may affect wildlife, wildlife, and humans worldwide.
Unfortunately, our knowledge of the global distribution of many infectious diseases is extremely poor. This geographic ignorance thwarts a variety of clinical, epidemiological, and public health studies. Although work in spatial epidemiology has long been necessary, the need is accentuated in the prevailing context of Covid-19.
Credit for bats photo: Flicker