The human impact on the environment is expected to have complex effects on disease; from climate change to a loss of biodiversity, there are several factors that could result in an increase in infectious outbreaks.
Several factors contribute to increasing the likelihood of outbreaks of infectious diseases. One is that a warmer planet allows disease vectors to travel and survive in areas in which they previously could not do so. A well-known example of this is how the Culex mosquito, which carries the West Nile virus, has spread. Many scientists argue that climate change is the most significant factor contributing to the spread of the West Nile virus.
Researchers from the University of South Florida, the University of Wisconsin–Madison and the University of Notre Dame have found evidence that suggests that as the planet heats up, cooler climates are more likely to see an increase in infectious diseases. The “thermal mismatch” hypothesis explains there is a host susceptibility to an emerging infectious disease (this is due to parasites typically having broader thermal limits than hosts). The researchers note that increased rates of infections in other species can also portend an increase in infections that spread to humans.
Alongside this, the increasing amount of habitat destruction is forcing animals to move out of their natural environment and into human settlements. This is a result of the clearance of rainforests to create settlements, roads, farmland etc. An increase in human contact as a result of this forest clearance means there is a greater chance of a mutation leading to a virus crossing the species barrier.
Poor social and environmental conditions in many developing countries can also negatively contribute to the impact of an outbreak of disease.
A study published in PLOS One reveals that almost half of the population is unaware of this relationship between climate change and infectious diseases. The results showed that 48.9% of the participants had never before considered the relationship between climate change and infectious diseases. The same research found that a large percentage of people were afraid of contracting an infectious disease (64.6%), with a difference found across countries. These results reveal a lack of knowledge among the general public of one of the consequences of climate change.
The COVID-19 pandemic is also the result of human impact on the environment. SARS-CoV-2 has an ecological origin in bat populations. Usually, close contact between humans and bats is quite rare, so it is more likely that the transmission from bat to human happened through another species. Some of the first cases of COVID-19 had a link to a wholesale food market in Wuhan, China. This suggests that the intermediate animal species was potentially found in this food market, perhaps an animal which had been sold for its meat in the market.
As the global demand for meat increases, the chance of zoonotic viruses mutating to infect humans also increases. Not only do we have the chance of a virus jumping from a domestic animal (H1N1, also known as swine flu which originated in pigs), but with the added clearance of natural habitats as discussed earlier, we also introduce a greater variety of wild animals and their respective microbiome into the mix. The desire for cheap meat can sometimes result in poor animal husbandry standards as animals are overcrowded into pens to try and increase profit made per square metre of land.
The race to find a vaccine for COVID-19 could be repeated all too frequently in the future when another pandemic occurs. The risks from human impact on the environment show that the chances of another pandemic occurring are increasing and that it is more of a question of when, and not if, it happens again.
#EnvironmentalImpact #ClimateChange #HabitatLoss #Pandemic #Vaccine
Sources
https://phys.org/news/2020-11-effect-climate-infectious-diseases-unknown.html
https://www.eurekalert.org/pub_releases/2020-11/uadb-eoc112520.php
https://phys.org/news/2020-11-global-species-planet-infectious-diseases.html
https://www.cdc.gov/coronavirus/2019-ncov/daily-life-coping/animals.html
https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200423-sitrep-94-covid-19.pdf?sfvrsn=b8304bf0_2#:~:text=Retrospective%20investigations%20by%20Chinese%20authorities,%2C%20some%20did%20not