COVID-19 may only be the beginning of global pandemics – a future scenario in which climate change may also play a role.
"We have entered a pandemic era," said a recent study in the journal Cell. Written by Dr. Anthony Fauci and medical historian Dr. David Morens, both of the National Institute of Allergy and Infectious Diseases, the study paints a picture of a future where pandemics become more numerous.
“I don’t have a crystal ball, but what we are seeing looks very much like an acceleration of pandemics,“ Morens told BuzzFeed News. Causes he cited include deforestation, urban crowding and wet markets for wild game.
But climate change's possible role is complicated: We know that the virus survives longer in cold temperatures than hot, so that could mean that a warmer planet would slow the spread of the disease, said meteorologist Jeff Masters, who writes for Yale Climate Connections. On the other hand, he said heat waves cause people to spend more time indoors in air-conditioned spaces, where the spread of the disease increases.
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"Thus, Florida had a difficult time with COVID-19 this summer, despite the fact that some parts of Florida recorded their hottest summer on record," Masters told USA TODAY. "These complexities make it difficult to judge how climate change may be affecting COVID-19."
Warming creates 'opportunity' for pathogens
Some scientists do believe warming will play a bigger role in future pandemics.
"We do know that climate change alters how we relate to other species on Earth and that matters to our health and our risk for infections," said Dr. Aaron Bernstein, director of Harvard University's T.H. Chan C-CHANGE program.
"As the planet heats up, animals big and small, on land and in the sea, are headed to the poles to get out of the heat," he said. "That means animals are coming into contact with other animals they normally wouldn’t, and that creates an opportunity for pathogens to get into new hosts."
In addition, Masters said the diseases of most concern globally that are worsened by climate change are the ones spread by mosquitoes, since mosquitoes like it hot and wet – conditions that are becoming increasingly common because of global warming. Malaria, Zika, chikungunya, dengue fever and the West Nile virus are all expected to spread into areas where they currently are not endemic, he said. Tick-borne diseases such as Lyme disease will also spread.
Bernstein said climate change has already made conditions more favorable to the spread of some infectious diseases, including Lyme disease, waterborne diseases such as Vibrio parahaemolyticus (which causes vomiting and diarrhea) and mosquito-borne diseases such as malaria and dengue fever.
"Future risks are not easy to foretell, but climate change hits hard on several fronts that matter to when and where pathogens appear, including temperature and rainfall patterns," Bernstein said. "To help limit the risk of infectious diseases, we should do all we can to vastly reduce greenhouse gas emissions and limit global warming to 1.5 degrees."
As for whether climate change could exacerbate future pandemics, Morens told USA TODAY it is too early to draw definitive conclusions.
"One might imagine that if climate change causes further environmental degradation and change (beyond what humans are already doing), then we are likely to see more of these diseases," he said. "But one could equally argue that we will see less. These are big questions to which we may not have good answers for decades, or even centuries to come.
"But at the end of the day, for many reasons, it is hard to imagine that climate change will be anything good for human health."
Climate change is a 'threat multiplier'
One expert said that almost certainly, the impacts of pandemics such as COVID are exacerbated by climate change.
Meteorologist Michael Mann of Penn State University called climate change a "threat multiplier," meaning "it amplifies existing challenges and threats by increasing our vulnerability and reducing our adaptive capacity."
He said to consider, for example, the situation in Puerto Rico, where many people have died of COVID-19 for the simple reason that they have not yet recovered, in terms of their public health infrastructure, from the devastating impacts of Hurricane Maria three years ago.
"There is no doubt in my mind that the storm was made more destructive by unusually warm tropical Atlantic sea-surface temperatures, which provide more energy and moisture for the storm," Mann said. "This anomalous warmth can only be explained taking into account human-caused climate change."
He said a case can also be made for at least an indirect connection between COVID-19 and climate change. Environmental degradation, including deforestation, the destruction of rain forests and natural habitats for development may be displacing exotic disease-carrying creatures in a way that does favor increased human contact.
"These same activities – deforestation in particular – are also leading to increased carbon emissions, which are behind human-caused climate change," Mann said.
This article originally appeared on USA TODAY: Climate change and COVID-19: Does global warming fuel pandemics?