The overlooked danger: The biohazards of climate change

This commentary is one in a series on climate change, national security, and the Arctic produced in association with CERL’s recent conference, Circling the Arctic: Security and the Rule of Law in a Changing North. The conference was organized by the University of Pennsylvania’s Center for Ethics and the Rule of the Law and Annenberg Public Policy Center, with support from the Wilson Center’s Polar Institute.

The thought of climate change often evokes a familiar collection of fears and threats, including rising global temperatures, a greater number of extreme weather events, and increased threats to coastal development from rising sea levels. These risks reinforce and escalate the effects of each other in powerful ways, facilitating the rise of additional threats. One of those threats is the hastened spread of infectious diseases and pathogens. As the ongoing COVID-19 pandemic demonstrates, disease outbreaks can wreak cataclysmic havoc on our societies and economies. Treating them with the utmost urgency and attention is essential to our national security interests. Given the severity of the security risks, any future U.S. climate policy needs to include plans for disease and biohazard prevention and management.

Understanding the most common vectors and other means by which climate-related pathogens spread is essential to preparing for and responding to the risks they present. Recognizing this, the below identifies several ways in which changing climate patterns are affecting common disease vectors and provides examples of emerging threats in the Arctic and beyond.

Changing Climate Patterns Are Already Expanding Vector-Friendly Environments

A series of historic climate-related events compel serious study of the connections between climate and infectious disease. Since 1880, the average temperature of the Earth has risen slightly more than one degree Celsius. This increase has complex effects on the environments in which pathogens grow, including strengthening the lifecycle of pathogens and their vectors and increasing the geographic scope of pathogenic activity. As discussed below, the Arctic is melting at a blistering pace, revealing pathogens and other biohazardous secrets that have been frozen for millennia. Animals across the world, forced by climate change to seek shelter outside of their natural habitats, are spreading disease to new environments. The proliferation of mosquitos due to unusually warm and wet climes is also spreading viruses and other pathogens beyond their usual territories.

Climate change has led to heavier rainfall and more powerful tropical storms in some areas of the world while inducing droughts and heat waves in others. Such extreme weather can accelerate the breeding cycles for insects carrying infectious diseases (“insect vectors”). For example, in areas experiencing higher levels of precipitation, stagnant puddles of rainwater provide ideal breeding conditions for such vectors. In areas experiencing drought, humans may begin to store more rainwater, which can create the same hospitable breeding environments. Researchers also have found that higher temperatures decrease the amount of time required for mosquitos to complete their life cycle, leading to higher mosquito populations.

The mosquito is the leading insect vector capable of prolifically spreading disease over vast territory. Indeed, the Centers for Disease Control and Prevention already considers the mosquito to be the world’s most dangerous animal due to the staggering death toll brought on by the insect’s spread of diseases like malaria, dengue, and yellow fever. Today, mosquitos are expanding their geographic range and reaching higher elevations. Researchers have concluded that because of habitat expansion, two major disease-spreading mosquito species, Aedes aegypti and Aedes albopictus, could be in contact with half the world’s population by 2050. Others have predicted that up to one billion more people could be exposed to the diseases borne by these mosquitos by 2100.

We have already seen the impact of climate change and environmental degradation on mosquito-borne disease. For example, dengue fever already affects areas where 40% of the world resides (approximately three billion people). In a trend that shows no signs of waning, the number of dengue cases worldwide has increased by a multiple of 30 over the last 30 years due to urbanization, travel, and climate change. A study in Lancet concluded that as a result of climate change, by 2085, 5-6 billion people are expected to live in areas endemic with dengue fever, whereas without climate change, that number would be only 3-5 billion. Rates of malaria infection also tend to rise in areas with increased rainfall, a phenomenon documented in the Punjab area of India after monsoons where rates of malaria increased fivefold after El Niño.

While mosquitos and ticks are model examples of vector-borne diseases, they are not the only pathways for pathogens to spread. Changes in sea surface temperatures and salinity levels also bolster bacteria breeding. Within the ocean, an altered hydrologic cycle and run-off from human activities have reduced the salinity in some coastal wetlands and estuaries and increased the sea surface temperature in general. These changes have supported the growth of Vibrio spp, a naturally occurring bacteria that prefers warm and low salinity seawater. Members of the Vibrionaceae family can cause gastroenteritis, septicemia, and more. Vibrionaceae cholerae, in particular, is the cause for approximately three million cases of cholera per year.

Emerging Threats in the Arctic and Beyond

The Arctic is a particularly dynamic region that could become a hotbed of both known and novel diseases as it continues to warm at two to three times the rate of the rest of the globe. The frozen, oxygen-free environment of the Arctic traps pathogens in ice that may remain viable while frozen and potentially deadly when released. Research on glacial ice cores published earlier this year found 33 viral strains trapped in the ice, 28 of which were previously unknown and potentially hazardous.

The dangers of previously frozen pathogens are not hypotheticals. In 2016, melting Siberian permafrost released anthrax previously frozen in long deceased animal carcasses that had been trapped in the frozen soil in the Yamalo-Nenets region of Russia. The outbreak hospitalized 20 adults and killed one young child. This was not an isolated incident of defrosted pathogens infecting living humans. In 2017, a researcher contracted a rare skin infection while exhuming a dead seal. Doctors identified it as a possible case of seal finger, a rapidly spreading infection that was regularly caught by seal hunters nearly 1,000 years ago.

Flora and fauna shifts also are affecting disease spread in the Arctic. For example, as ice and snow melt make territory at lower latitudes more hospitable to life, boreal forests expand north into the Arctic, bringing forest flora and fauna—and associated pathogens such as Giardia—with them. Animals that will likely expand their territory in synchrony with the forests include foxes and voles, which can carry the parasite Echinococcus multilocularis. More extreme weather incidents, melting permafrost, and/or shifting water patterns may also damage Arctic water flows and sanitation structures, leading to communicable health risks like cholera, diarrhea, dysentery, hepatitis A, typhoid, and polio. Milder winters and earlier springs in Sweden already have been correlated with a rise in tick-borne encephalitis, and a similar finding can be observed in northwestern Canada. Higher rodent populations, which are associated with warmer climates, are suspected to be responsible for outbreaks of Puumala virus in Sweden that afflicted 313 out of every 100,000 inhabitants in the country. Mosquitos first brought West Nile to the United States in 1999, but as their populations have moved north in the last 20 years with temperature shifts, they have spread the disease at least as far as Manitoba, Canada.

While disease may not be on the top of people’s minds when they think about climate change, the threats it poses are real and pose a global concern. COVID-19 has taught all of us how quickly a virus can spread across today’s hyperconnected globe, with dramatic and devastating security consequences.
The Arctic, as a particularly vulnerable region, may end up serving as the source of many new diseases. Given the Arctic’s geographic location, contagions unearthed there could easily spread to the United States, its allies, its adversaries, and the rest of the globe alike.

It is imperative that climate-response policies generally and Arctic policies more specifically include plans for addressing the release and spread of novel and known biohazards and infectious diseases. Monitoring, studying, and preparing for climate-related pathogen spread in a coordinated fashion is essential to creating a comprehensive domestic and international national security strategy. As Robinson Meyer wrote in The Atlantic in 2017, “Climate change … could awaken Earth’s forgotten pathogens. It is one of the most bizarre symptoms of global warming. And it has already begun to happen.” The time for governments to act is now.

Souvik Chatterjee is an M.P.A. candidate at Columbia University’s School of International Affairs in the Class of 2021. Henry Scherck and Jane Wang are J.D. candidates at the University of Pennsylvania Carey Law School in the Class of 2022. All three authors were members of CERL’s Summer 2020 class of interns.

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