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How Climate Change is Transmitting Virus Between Mammals

Climate Change - The Future Pandemic

It’s been 2-3 years since the Covid-19 pandemic. No one saw it coming as there wasn’t any build-up or hints that a global pandemic will hit us. As a result, the pandemic came at us with a surprise, leaving trauma and scars for the unfortunate. But what if, scientists have identified the potential threat of a future pandemic, and it’s been building up since the start of climate change?



The Future Threat

Published in April 2022, Nature wrote a journal which revealed that by 2070, climate change has the potential of spreading 4,000 viruses between mammals. In addition, Nature also reported that this would equate to 15,000 new cases of mammals transmitting viruses to other mammals. Authors of Nature suggested that their findings have led them to believe that climate change will actually become the dominant driver of cross-species virus transmissions.


This is due to the fact that climate change is forcing different animals to migrate out of hotter climates, causing numerous different species of animals to create contact with each other for the first time. Alarmingly, a scientific review in 2008 revealed that half of the 40,000 species around the world have already started migrating due to climate change. Animals are migrating to cooler temperatures like the Earth’s poles in which statistics reveal that land animals are moving 10 miles polewards per decade whilst marine species are moving 45 miles polewards per decade. Scientists believe that these forceful migrations occur in species-rich ecosystems at high elevations like the areas of Africa and Asia. This also includes areas with high human population like eastern China, Indonesia, India, and even the Philippines.


Scientists predict that if the planet warms by no more than 2℃ than the pre-industrial temperatures this century alone, the number of “first-time meetings” of numerous different species will double by 2070. Gregory Albery, a diseases ecologist at Georgetown University expressed, “This work (Nature’s journal) provides us with more incontrovertible evidence that the coming decades will not only be hotter, but sicker.” In other words, the upcoming decades will see an increased risk and greater hotspots of disease transmission between animals and humans alike.



The Model

To predict how these viruses might spread in the future, Albery and his colleagues developed a model that is then tested by running simulations over a 5-year period using 3139 mammal species. They did so by intertwining different models of virus transmissions and species distribution, specifically on mammals since they serve the largest threat to humans. They simulated numerous climate change scenarios like an increase of 2℃ in global temperatures, continued reliance on fossil fuels, and rapid land degradation. The model they developed looks a little something like this:



The model predicts where mammals might move to seek for colder habitats to live in as the global temperature keeps increasing. The model also predicts the chances for a virus to transmit between species and where this transmission might occur based on the potential meeting points of these species. However, there are certain limitations to the model.


President of the American Society of Tropical Medicine and Hygiene, Daniel Bausch, points out that human activity may actually disrupt animal migration, limiting the encounters. This includes urbanization or highway and dam building. He also added that there may certainly be hotspots on the model, but there will surely be cold spots too since these areas have become uninhabitable for these migrating mammals. In the end, Bausch concluded that the predictions of virus transmission is a tricky obstacle to tackle.


Researchers also had to make assumptions regarding how wide and far species would most likely spread in the search for colder temperatures. However, there are some factors that are harder to assume like whether mammals will be able to adapt to the local conditions or factors like if these mammals can even physically cross barriers in landscapes. Therefore, global-change ecologist Ignacio Morales-Castilla of the University of Alcalá in Spain, points out that forecasting like the model above requires the inclusion of unrealistic assumptions. Then again, he also mentioned that the model is still “technically impeccable”, leaving a strong reason to believe that the model is still somewhat accurate.


The Spillover

This growing threat of virus transmission between mammals due to climate change also becomes a threat for humans. The transmission of viruses between animals and humans is called zoonotic diseases. Matthew Aliota, a professor Department of Veterinary and Biomedical Sciences at the University of Minnesota expresses his concerns on this matter, “Unfortunately, we will continue to see new zoonotic disease events with increasing frequency and scope,” What professor Aliota seems to suggest here is that disease events like Covid-19, since Covid-19 is a zoonotic disease itself, will have the potential to occur more often and at a higher scale. In other words, climate change is increasing the risk of another zoonotic spillover.


Currently, there are around at least 10,000 viruses that have the capabilities of infecting humans. However, at present time, the majority of these viruses are still being silently transmitted in between animals only. However, as these animals migrate seeking a colder climate, they also end up carrying these viruses with them. Therefore, the threat of zoonotic disease spread becomes impending as these animals and their viruses encounter each other for the first time. However, it is safe to say that there are still many factors that may reduce the risk of virus transmission between animals and humans. This may include an increase of investment in health care and if just by chance, a virus is unable to infect humans.


Accountable for the initial transmission of the Covid-19 virus, an animal that comes on top as the biggest threat of zoonotic diseases are bats. This is due to the fact that bats are the only mammals with the ability to fly. It is believed that bats will be accountable for almost 90% of the first encounters between species. It is also believed that these first encounters will happen across elevated tropical regions like Africa and Southeast Asia. Therefore, humans might develop behavior to avoid bats but Albery clearly expressed that punishing bats by the means of culling or migration prevention will only make matters worse since this drives greater dispersal, greater transmission, and weaker health.



The Conclusion

So, what now? Well, this zoonotic spillover is inevitable as it has already begun just as we experienced with the Covid-19 pandemic. Various species of land animals have already begun migrating in the conquest of locating cooler habitats to live in. It’s also safe to say that these first encounters in between species have more likely than not occurred already. This means that the silent circulation of diseases between animals have already begun.


So, there are a few things to keep in mind. First and foremost, it is essential to accept the fact that this zoonotic spillover will not cease to stop even if the world acts quickly on fighting climate change. However, it is still important that we keep fighting against climate change. The prolonged effects of climate change will continue to drive animals out of their original habitats in order to find colder ones. Therefore, by fighting against climate change, it will reduce the probability that these animals will continue to look for newer habitats.


Another thing to keep in mind is that humans have learned a lot from the Covid-19 pandemic. After killing a reported amount of 6 million deaths and an estimated amount of 15 million deaths, the Covid-19 pandemic served as a wake-up call that should prepare humans for future pandemics. Therefore, an increase in investment for global healthcare will prove to be useful against the impending threat of future zoonotic spillover.




References:

  1. Covid-19 pandemic [Internet]. Wikipedia. Wikimedia Foundation; 2022 [cited 2022May17]. Available from: https://en.wikipedia.org/wiki/COVID-19_pandemic

  2. Dunne D. Climate change 'already' raising risk of virus spread between mammals [Internet]. Carbon Brief. 2022 [cited 2022May17]. Available from: https://www.carbonbrief.org/climate-change-already-raising-risk-of-virus-spread-between-mammals/

  3. Yadav I. In 50 years, increased risks of viruses spread by mammals, and several pandemics [Internet]. Hindustan Times. 2022 [cited 2022May17]. Available from: https://www.hindustantimes.com/science/in-50-years-15-000-new-cases-likely-of-mammals-transmitting-viruses-to-mammals-101651307498939.html

  4. Gilbert N. Climate change will force new animal encounters - and boost viral outbreaks [Internet]. Nature News. Nature Publishing Group; 2022 [cited 2022May17]. Available from: https://www.nature.com/articles/d41586-022-01198-w

  5. Fit. Climate change will increase virus spread from animals to humans, study says [Internet]. TheQuint. 2022 [cited 2022May17]. Available from: https://www.thequint.com/fit/climate-change-virus-spillover-transmission-wild-animals-to-humans-covid-swine-bird-flu#read-more

  6. Wong C. Climate change may increase the spread of viruses between land mammals [Internet]. New Scientist. New Scientist; 2022 [cited 2022May17]. Available from: https://www.newscientist.com/article/2317959-climate-change-may-increase-the-spread-of-viruses-between-land-mammals/

  7. Zoonotic Diseases [Internet]. Centers for Disease Control and Prevention. Centers for Disease Control and Prevention; 2021 [cited 2022May17]. Available from: https://www.cdc.gov/onehealth/basics/zoonotic-diseases.html



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