In recent years, pandemics have seemed to make an alarming return. Though many believed that modern science and medicine had subdued the global threat of infectious diseases, outbreaks like HIV/AIDS, several flu pandemics, and most recently, COVID-19, have shown that pandemics are not a thing of the past. But what’s causing this resurgence of pandemics? Many scientists believe that human activity, specifically our impact on the environment, plays a significant role.
A Glimpse into the History of Pandemics
Pandemics are not new. Historically, the world has faced several devastating outbreaks. In the Middle Ages, the Black Death (plague) wiped out a large portion of Europe's population. After the First World War, the Spanish flu claimed millions of lives worldwide.
For a while, advancements in science helped humanity gain the upper hand against infectious diseases. Vaccines eradicated smallpox, and polio has almost been eliminated. Antibiotics became widely available, treating bacterial infections, and more recently, antivirals have helped control certain viruses.
But despite these scientific achievements, pandemics have returned in recent decades. Starting in the 1980s, we saw the spread of HIV/AIDS, followed by outbreaks of various flu strains, SARS, and now COVID-19, which has claimed over 7 million lives to date. The pressing question remains: why are pandemics making a comeback?
Unbalanced Ecosystems and Their Role in Pandemics
Healthy ecosystems do much more than provide food and clean water. They also regulate diseases, keeping pathogens in check. In a balanced ecosystem, predators control the populations of herbivores, which in turn manage plant growth. This harmony makes it harder for diseases to spread from animals to humans in ways that could spark pandemics.
However, when human activities disturb ecosystems - through climate change, deforestation, and biodiversity loss, this balance is disrupted, making it easier for diseases to emerge and spread.
For instance, climate change is affecting the distribution of plants and animals. Mosquitoes, which carry diseases like malaria and dengue, are now spreading into areas that were once too cold for them, increasing the risk of disease transmission to humans. Studies on dengue fever in China support the idea that as the planet warms, more people will be at risk.
Similarly, biodiversity loss can create new opportunities for diseases to spread. For example, when ranchers cleared large areas of forest in South America for cattle grazing in the early 20th century, they unknowingly set the stage for a massive outbreak of rabies. Blood-feeding vampire bats, which normally lived in forests, found an abundance of food in the form of cattle. Without predators to control their numbers, the bat population exploded, and so did rabies infections, as these bats often carry the rabies virus.
Human encroachment on natural ecosystems, coupled with agricultural and urban development, also increases the likelihood of humans and domestic animals being exposed to pathogens usually restricted to wildlife. One such case is HIV, which is thought to have entered human populations when apes were slaughtered for food in Africa. The virus then spread globally through travel and trade. Similarly, bats are believed to be the original carriers of the virus that caused the COVID-19 pandemic.
The Ultimate and Proximate Causes of Pandemics
To fully understand why pandemics occur, it is essential to distinguish between ultimate causes and proximate causes. Ultimate causes are the larger, high-level factors, such as climate change, biodiversity loss, and global population growth, while proximate causes are the immediate, direct factors, like increased human-wildlife contact.
In the case of HIV, for example, the virus spread when humans came into contact with the infected blood of apes. This direct interaction is the proximate cause. However, the ultimate cause lies deeper: people hunted and ate apes because of poverty and hunger, which in turn was driven by economic and environmental pressures.
Understanding this distinction is crucial because while public health efforts often focus on dealing with proximate causes—such as social distancing, vaccinations, and lockdowns to stop the spread of viruses—we sometimes neglect the ultimate causes. Addressing only the proximate causes is like treating the symptoms of a disease without addressing its root cause.
Taking a Planetary Health Approach
A promising solution to prevent future pandemics lies in adopting a "planetary health" approach. This concept is based on the understanding that human health is closely linked to the health of natural systems. By protecting and nurturing the planet, we can also safeguard ourselves from pandemics and other health crises.
The planetary health approach calls for tackling the ultimate drivers of pandemics, such as climate change and biodiversity loss, while also addressing the proximate causes. For instance, reducing carbon emissions, protecting endangered species, and preserving natural habitats would not only combat environmental degradation but also reduce the risk of disease outbreaks.
There is growing recognition of the need for this approach, with many universities now teaching planetary health concepts across various disciplines, including environmental science and public health. By equipping future generations with the knowledge and tools to address both the proximate and ultimate causes of pandemics, we can reduce the likelihood of future outbreaks.
The Path Forward
As global challenges like climate change, biodiversity loss, and population displacement continue to intensify, the risk of pandemics will only increase. It is crucial to take a long-term, holistic view of these issues.
Pandemics are not just a health crisis; they are also a symptom of deeper environmental imbalances. By adopting a planetary health approach, we can work towards a future where both people and the planet can thrive.
In conclusion, while scientific advancements have brought us vaccines and treatments to combat pandemics, we must not forget the larger picture. The health of our planet is directly tied to the health of its inhabitants. If we want to prevent future pandemics, we need to address the root causes—climate change, biodiversity loss, and environmental degradation. Only then can we hope to build a safer, healthier world for all.
