When Benjamin Franklin penned the phrase, “an ounce of prevention is worth a pound of cure,” he was urging citizens to use preventive measures to stop fires in houses and commercial shops. It was good advice, prompting a public awareness campaign about how to prevent fires, and just as important, establishing the professional Union Fire Company in Philadelphia. This combination of public awareness and professional training and practices put Philadelphia at the top of the list of American cities when it came to fire safety.
Following the wisdom of “an ounce of prevention …” could provide a key guiding principle to averting the next infectious disease pandemic. Indeed, the response to the current COVID-19 pandemic has included public awareness messaging to prevent its spread: hand washing; social distancing; mask wearing. Vaccines, now rolling out across the globe, are another critical action to halt the contagion. But there’s a deeper level of prevention that epidemiologists are warning us to take heed of, and that’s the impact of climate change and environmental degradation on the spread of infectious disease.
The environment and pandemics – what’s the connection?
Viruses are not new to the planet, and they are plentiful. Scientists estimate there are at least 1.6 million viruses living in mammals and birds, and they’ve identified about 700,000 with the potential to infect humans. Technically not alive, a virus needs a living host to reproduce and spread. The viruses found in wild animals can reproduce and thrive without hurting their host. But when those viruses find their way into a human host, the potential for deadly harm begins to unfold. Called zoonotic diseases, their pathways have become wider as environmental and climate changes facilitate their spread.
“We are living in the age of pandemics, and the fundamental reason is that we failed to live in harmony with nature.”
Peter Piot, co-discovered the Ebola virus in 1976
Factors such as deforestation, habitat loss, diminishing biodiversity, and warmer temperatures may individually or in combination interact to bring viruses closer to humans. “We are living in the age of pandemics,” says Peter Piot, head of the London School of Hygiene & Tropical Medicine, and who co-discovered the Ebola virus in 1976. “… and the fundamental reason is that we failed to live in harmony with nature,” he concludes.
Deforestation and habitat destruction
Worldwide clearing of forests, primarily for large-scale agricultural development such as raising cattle and palm oil production, proceeds at the alarming clip of 10 million hectares per year – an area larger than the size of Indiana every year. What happens when land is deforested? The balance of a biodiverse environment is thrown out of whack, with some plants and animals dying out altogether, and others becoming tougher and more abundant because there is less competition for resources such as food, water and habitat.
These tougher surviving species are now closer to inhabited areas, and their hardiness makes them ideal carriers of disease. Areas of west Africa have experienced thousands of cases and deaths from Lassa fever, a virus carried by a mouse species thriving on plantations and household areas that used to contain forests.
Additionally, animals that once were not in close contact with humans now become hunted and traded in wild animal markets, becoming a lethal vector for disease spread. Wild animal wet markets, such as the one in China widely thought to be the original source of the current pandemic, are found throughout the world. The debate surrounding efforts to ban these markets has highlighted that they are often a significant source of food for people in low-income rural areas. Problems of food insecurity and poor living conditions become more pronounced as land is cleared and people are confined to smaller, more crowded areas. These problems open up yet another path for disease spread via habitat destruction.
A biodiverse environment – the natural variety of plants, animals, and organisms – is a good example of collective solidarity. Together, all of these elements contribute to healthy air, water and land, and maintain a system of checks and balances so that harmful pathogens don’t overcome the entire ecosystem. As land changes from a natural state into farmland or suburban development, researchers find that not only are humans in closer proximity to disease spreading animals, but there’s actually an increase of those animals, according to an article in Nature. After reviewing 3.2 million records from several hundred ecological studies around the world, researchers noted population increases in 143 mammals such as bats, rodents and various primates most capable of transmitting disease to humans.
As land changes from a natural state into farmland or suburban development, researchers find that not only are humans in closer proximity to disease spreading animals, but there’s actually an increase of those animals.
Fewer species of migratory birds in the U.S. provide an example of the harm that comes with diminished biodiversity. West Nile disease spiked when the thinned out bird species infected mosquitoes at a much higher rate than when more bird species existed. The tough birds were West Nile carriers, and their unfettered access to mosquitoes formed an efficient chain for transmission – and the last link was to humans.
The West Nile disease example also demonstrates the domino effect of climate change. Weather patterns now swing with increasing frequency between extremes of drought and flooding. Mosquitos flourish in both environments, but frogs and dragonflies – the mosquitos’ natural predators – don’t fair so well under drought, leading to an even bigger mosquito boom. Mosquitos are efficient at moving disease from animals to humans. A bigger population of mosquitos shifts disease transmission into overdrive, illustrating a core principle of contagion.
As temperatures warm throughout the world, so too does the range of disease-carrying ticks and mosquitos. Warmer temperatures not only expand their geographic range, but experts say as temperatures rise, it takes less time to become a biting adult capable of passing on disease. Dengue fever, an infectious disease causing debilitating joint pain, internal bleeding and fever, is passed on through mosquitos. Afflicting nearly 400 million people a year, South America and Africa have suffered especially high rates of the disease. In the U.S., Hawaii, Florida and Texas have experienced rising cases of locally acquired dengue fever, and a local transmission case appeared in New York in 2013.
Collaborate, don’t obliterate
Just as in Ben Franklin’s approach to containing fires, there are important roles for individuals, professionals, and policy makers in this public health fight against future pandemics. Scientists have sounded the alarm by identifying the human activities that create fertile ground for infectious disease spread. Policy makers, public health workers and environmentalists can chart a course to preserve, rather than further degrade the environment. Individuals make choices everyday that impact the environment, from the policies we urge our legislators to support, to how much palm oil and animals products we choose to consume.
From actions big and small, a sustainable, safe future is possible. The time, effort and expense may seem prohibitively large until you consider the $26 trillion price tag it’s estimated has already been spent on just this one virus. The truth is, the next “once in a century” infectious disease could happen any time if we don’t learn to collaborate with, rather then obliterate, nature.