October 14, 2020
The tipping point: Climate crises and zoonotic disease
The emergence of COVID-19 has changed our lives for a long time to come. With 38 million confirmed cases and over 1 million deaths globally, the response to this disease has been on a scale never seen before. For years, science has warned policymakers of the consequences of rising greenhouse gas emissions and of the intimate link between the climate crisis and global health—but for the vast part its cries fell upon deaf ears.
Man-made greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth. Though many people still view the climate crisis as a geographic and physical phenomenon, there is a very real human and biological side too, with a host of related global health issues. Whilst there have been many warning shots fired by nature over the past decade, such as Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), and Ebola, we have not fully taken heed of these. If left unchecked, the climate crisis will cause hundreds of millions of deaths across the planet in the coming decades.
Pathophysiologic effects of climate change
Broadly speaking, the effects of climate change on human health can be divided into four categories: heat stroke and cardiovascular diseases, air pollutants and respiratory disorders, malnutrition and water shortages, and infectious diseases.
This last category, the rapid growth in type and virulence of infectious diseases, particularly those caused by RNA viruses, is of most immediate importance. Many of these infectious diseases are zoonotic in origin: caused by germs that spread between animals and people, and they account for 60 percent of all disease and 75 percent of all new emerging infections, and their prevalence has tripled in the last decade. This increase is largely driven by anthropogenic changes. The quest for economic development is destroying biodiversity: as human beings alter patterns of land use for agriculture, trade, livestock rearing, and travel, they push farms and populations closer to the wild and thus increase the chance for the spread of infectious disease by providing pathogens more opportunity to cross species and establish localized emergence. The novel coronavirus SARS-CoV-2 is itself thought to have initially spread in a wet market in Eastern China, and the majority of recent major human infectious disease outbreaks worldwide, such as SARS, MERS, and HIV/AIDS all originated in animals and spread to humans through close contact.
There are various “routes of entry” for these pathogens to infect human hosts. While direct zoonotic transfer between a vector (mosquito, bat, poultry, mammal, etc.) and a person is a common route of entry for pathogens to infect human hosts, there are three other potential pathways that need to be carefully monitored in the future, and their importance will increase as the climate crisis begins to alter the physical properties and underlying chemistry of the planet.
The first is transmission via soil-borne agents, which may enter food chains and pose a risk to global food security. The second is water-borne agents entering human water supplies such as groundwater and thus capable of rapid distribution among large populations. The third, and the biggest potential unknown, is ice-based release. Environmental ice appears to be an important abiotic reservoir for pathogenic microbes. Rising temperatures are melting vast volumes of permafrost and releasing ice from retreating glaciers and melting ice caps. As this frozen water melts, there is a potential risk of dormant, ancient microbial and viral species being reactivated and released into global systems, agents that have been locked away in the frozen layers and theoretically out of contact with anything alive today. There is no way of knowing how dangerous they could potentially be when they interact with human immune systems.
Building a global prevention system
In 2015, the WHO was asked by its member organizations to create a ‘Blueprint for Action’ to prevent epidemics and stop the outbreaks from turning into public health emergencies. At the time, ten emerging infectious diseases were added to this list. Since then, to try to protect ourselves against these natural pathogens, various international organizations like GAVI, WHO, WEF, and the CDC have also released “watch lists” to safeguard against a low probability but high consequence event. In 2018, the idea was floated to create a new category in this list, which was named “Disease X.”
This placeholder acknowledged the potential for a future epidemic caused by an unknown pathogen and by its inclusion challenged the WHO to ensure their planning and capabilities were flexible enough to adapt to such an event. Such agility would become vital for generating ideas in the global scientific community that would reduce the time lag between the identification of viral outbreaks and the approval of vaccines and treatments and has been critical in current efforts to move from early detection of hotspots to sequencing entire viral genomes to developing candidate vaccines and possible therapeutic strategies against COVID-19.
It is necessary that any global strategy for preventing pandemics includes monitoring the climate, particularly in the face of these drastic changes caused by human behavior. As previously proposed by Dr. David Bray, a global framework for pandemic prevention would require a significant multi-stakeholder effort to bring the necessary actors and technologies together to set up such a system. Given the multiple disciplines involved, it will require the cross-collaboration amongst environmental scientists, data scientists, animal and human health professionals, and many other fields.
Technological data interoperability will be fundamental to success: building the cloud-based cyber infrastructure to process inputs from multiple systems (weather data, satellite photography, Google searches, social media posts, CDC records, etc.) located at the edge, and triangulating these variables to develop mature signals for predicting hot spots. In many ways crudely modeled on the human body’s own immune system, such a framework would involve the following three key steps:
Step 1: Identification and Detection System
- A widespread, scalable network of sensors collecting continuous real time data in a secure manner and relaying this information digitally to a central command module. This central command center would act as a library to assess risks and learn from each interaction and event.
Step 2: Developing the Appropriate Mitigation Response
- Steps and processes to contain the spread of the agent and develop a neutralizing response or therapy, which would need to be released in a controlled, effective, and safe manner with minimal adverse consequences.
Step 3: Building a Scalable Global Distribution System
- Scale is critical, as is the ability to fine tune local responses to deliver this neutralizing agent through a global equitable distribution framework so that it is easily accessible by the vulnerable and poor alike.
In 2016, the people of the world watched as 157 world leaders from 196 countries gathered in Paris and crafted the climate accord, hoping it would create a healthier planet for future generations. Whilst we have made some progress, we still have a very long way to go.
The global response to COVID-19 has shown us that the international community can come together and create a synchronized, unprecedented mitigation response when faced with a systemic threat. Multiple stakeholders have joined forces to focus on producing an antidote to this virus on a scale never seen before in history. If we can work together to achieve these goals now, then surely the human spirit of cooperation and excellence will allow us to create a remedial response to the climate crisis. We must turn the clock back on our current unsustainable way of life and create a world in which we are not dependent on oil and natural gas and one where we live within our means to create a lasting legacy for mankind that we can be proud of.