Campus Queries: What environmental factors are linked to the coronavirus pandemic?
Campus Queries is a series in which readers and staff of The Daily Bruin present scientific questions that UCLA professors and experts must answer.
Question: Is there a link between environmental issues and the COVID-19 pandemic?
A: Habitat destruction, wildlife markets and climate change may be linked to zoonotic fallout like the one that caused the COVID-19 pandemic, while the link between biodiversity loss and the pandemic is less clear .
SARS-CoV-2, which causes COVID-19, is a zoonotic virus that likely originated from horseshoe bats in China, said Amandine Gamble, postdoctoral researcher at UCLA’s Lloyd-Smith Laboratory.
Zoonotic viruses spread from exclusive host animals to humans during a zoonotic spillover event, said Thomas Smith, professor of ecology and evolutionary biology at UCLA.
Zoonotic disease outbreaks are the result of increased contact between humans and wildlife due to processes such as deforestation and habitat destruction, Gamble said. For example, if forest fruit trees are disappearing due to deforestation, bats are more likely to go to people’s gardens to feed on cultivated fruit trees, thus creating opportunities for more zoonotic fallout. between wild animals and humans, she said.
A 2007 study by researchers at the University of Hong Kong warned that horseshoe bats naturally harbor viruses similar to SARS-CoV and that the practice of eating wild animals in southern China was a “time bomb” for the re-emergence of another SARS-like virus.
This study was published after the 2003 SARS outbreak in Hong Kong. Thirteen years later, the COVID-19 outbreak has occurred.
It is not known how SARS-CoV-2 started infecting humans, but researchers believe an intermediate host allowed transmission from bats to humans, Gamble said.
A popular theory for the intermediary of SARS-CoV-2 is that of pangolins, which are common in Chinese wildlife markets, but there is little evidence to support this theory, Gamble said. The virus detected in the pangolin was closely related, but not the same one that caused the pandemic, she said.
These types of spillover events are not exclusive to coronaviruses. Henipaviruses, another type of virus found in fruit bats, are transmitted directly from bats to humans in Bangladesh through the palm sap they drink, Gamble said. In Malaysia, henipaviruses are transmitted from bats to pigs in pig farms, while bats there eat fruit and pigs are infected, she added.
Wildlife markets are also a hotbed of transmission, as wild animals from all over the world are placed in small cages close to each other, Smith said. The animals defecate on top of each other and are often slaughtered next to each other, creating optimal conditions for the virus to be transferred from one animal to another, he said.
The link between biodiversity loss and zoonotic fallout is less clear. Biodiversity loss can be broadly defined as the decrease in the number and variety of species. Earth is currently experiencing its sixth mass extinction event, caused by human factors, according to a study supported by the National Autonomous University of Mexico and Stanford University.
It remains unclear whether the extinction event and zoonotic fallout are correlated.
âWe don’t know if having more species actually creates a better environment for the virus to replicate and evolve. â¦ So you might think that having more biodiversity will lead to more zoonotic spillover events, âGamble said. “But there is also what we call a ‘dilution effect’ – the more species you have available for the parasites, the less likely it is to be found in humans.”
However, zoonotic fallout is ultimately difficult to detect, making it difficult to quantify the correlation between biodiversity and fallout, she added.
When it comes to biodiversity loss and habitat destruction, it doesn’t take long for climate change to enter the conversation, Smith said. As the planet warms, humans and animals are moving to cooler places, he said.
âThat means there’s going to be a lot more of a mix – animals are going places they’ve never been before, and humans are too,â Smith said. âFrom a pandemic perspective, I think it’s possible to see a lot more fallout from this type of disease. It’s sort of the link between climate change and pandemics.
There have been reports of improved air quality due to the decrease in human activity during the pandemic. However, when carbon emissions fell sharply after past recessions, they rebounded and reversed any short-term emissions cuts, according to a BBC Future article. To achieve a long-term effect, there must be big changes, such as a shift towards clean energy, according to Glen Peters of the Center for International Climate and Environment Research in Oslo.
âI think as soon as a vaccine is discovered people will go back to driving their cars and doing as much as before,â Smith said. âThe hope is that this pandemic will be a wake-up call for people to think about how they are changing the climate and the biodiversity on which we all depend. “