As the world becomes accustomed to living with COVID-19, is there a chance that more pandemics will make an appearance in the future? Here's everything you need to know:
Where do pandemics come from?
Research has shown that many human pandemics originated with animals. This applies to HIV, smallpox, tuberculosis, Ebola, and COVID-19, to name a few. However, there is a biological process that needs to occur for a disease to transition from an animal to a human, and before it can spread among humans, according to the National Library of Medicine.
These are called zoonotic diseases, which are diseases caused by germs spread between animals and humans. They can spread in multiple ways, according to the CDC. This includes direct contact, indirect contact (through a vector like a mosquito or tick), through food, and through water. The diseases that come from each of these types are handled differently; however, all of them are likely to increase because of climate change.
There are five stages in the transition from an animal disease to a fully-human disease: exclusive to animals; primary human infections only; limited human-to-human transition; sustained human-to-human transition; and exclusive to humans. In order for a disease outbreak to be considered a pandemic, it needs to spread globally and have no natural immunity in humans. It also needs to cause some sort of disruption globally.
Scientists expect that pandemics may occur frequently in the future due to climate change increasing interactions between humans and animals.
What is the role of climate change in the spread of disease?
Climate change is likely to cause a rise in zoonotic diseases worldwide. This is primarily due to rising temperatures forcing animals to migrate into habitats that are beyond their usual boundaries. A study by Georgetown University, funded by the U.S. National Science Foundation (NSF), found that the global virome — the livable area for viruses — is expanding due to climate change. This is a direct result of habitat loss and the reduction of ecological niches.
An ecological niche is the most ideal area and conditions for a certain organism to live and it includes factors such as average temperature, terrain, access to food, as well as interactions with other organisms like predators. With the planet warming, the regions where certain animals can thrive are slowly moving, causing animals to migrate with them. With a shift in habitats, some species are now coming into contact with species they hadn't previously encountered, as well as humans.
Certain manmade actions have also contributed both to climate change and to the potential of pandemics. One of the biggest factors is deforestation, or the cutting down of forests for other purposes, including development or agriculture. The Amazon rainforest has been reduced by approximately 17 percent already, as reported by Time. It is also one of the most ecologically diverse habitats on Earth, containing around 40,000 plant species, 1,300 bird species, 3,000 fish species, 427 species of mammals, and 2.5 million different insects. Many of these species have to migrate in order to survive.
Animal migration expands the global virome since viruses require a host. Unusual contact between humans and animals due to migration leads viruses to have an easier time spreading and evolving, increasing the potential for an outbreak to balloon into a pandemic. Sam Scheiner, a program director in NSF's Division of Environmental Biology, explained how the "research shows that animal movements and interactions due to a warming climate might increase the number of viruses jumping between species." Bacterial infections will likely follow the same path.
Along with a heavy migration of species, the Amazon is also the source of much of modern medicine today. Approximately 120 prescription medicines originated from the rainforest and almost two-thirds of cancer medications originated from rainforest plants. Deforestation both increases the chances of causing a pandemic as well as curing it.
Another study published in the Proceedings of the National Academy of Sciences found that there is approximately a 38 percent chance of experiencing another pandemic like COVID-19 in our lifetime based on the statistics around the emergence of zoonotic disease and environmental change.
What can we do?
New diseases are likely going to become a more common occurrence, so the best thing to do is to be prepared for them. Grist recently released a list of five diseases that spread quicker in higher temperatures: Powassan virus, Chikungunya fever, Valley fever, Vibriosis, and Chagas' disease. Three of these are vector-borne, while one comes from shellfish, and one comes from a fungus. Increased temperatures also cause insect migration, which could spread more vector-borne diseases. Bacteria also tend to grow and spread faster in warmer environments.
It is also important to work to prevent pandemic-level outbreaks by sharing information on viruses found around the world. That way, development can begin on vaccines and medicines for diseases before they grow out of hand, ABC reports. It is much more difficult to handle a pandemic once it has taken off.
The biggest step, though, is to attack the root of the problem: climate change. There have been strides made to tackle climate change, like the Inflation Reduction Act of 2022, which contains the largest single climate package in U.S. history. The UN has also identified the climate crisis as one of the biggest issues facing the world today.
"We need to address spillover. And that means we need to protect habitats. We need to tackle climate change." said Dr. Aaron Bernstein, director of the Climate MD program at the Center for Climate, Health, and the Global Environment at Harvard University's Chan School of Public Health, "We get very little back relative to what we could get back for one dollar spent on post spillover intervention versus root cause prevention."