Climate Change and COVID-19 : What is the Connection?

By: Margaret Gadon MD MPH; Member, Strafford Climate Action

 

Many of us have been wondering: Is there a direct link between worsening climate and the evolution of the pandemic of COVID 19? Unfortunately, there is no clear link, but there are a lot of related factors. To understand these, it is useful to review the elements which foster disease spread. 

All diseases spread through a population as a function of the following triad: susceptible host, a microorganism (virus, bacteria, parasite) that can thrive and rapidly replicate, and a conducive environment. In layman’s terms, people have to be in close enough proximity, present in sufficient numbers, and the microbe has to be sufficiently infectious and multiply quickly enough, for a disease to spread rapidly in a population. Measles only became an endemic disease when man transitioned from living as a hunter gatherer to a pastoralist. This led to increased contact with animals who carried a related virus. The virus spread to man, mutated into measles, and then spread rapidly among the non immune farming community. Lyme disease is believed to have been present in the 18th century in New England. It receded when the trees were cut down and the environment no longer supported the disease carrying deer mice, and then recurred with the forest regrowth. 

COVID-19 initially spread in Wuhan because of high infectivity, high population density and easy accessibility of the intermediate host (bats) to humans. Had exposure occurred in a more rural community with a lower population density, it is unlikely that it would have become an epidemic.

 

So how does climate change play into this disease spread and the development ultimately of a pandemic? There does not seem to be a preferred climate for the COVID virus, so increasing warmth is not an issue. However, globally, climate change has led to local changes in population density and has caused a rise in air pollution. 

    Namely: 

• With increasing warmth comes aridization and movement of populations from rural to urban areas. Areas that were once wild are populated and we come into contact with disease carrying animals. The microbe jumps from the wild animal to humans, mutates and finds a welcoming environment in man. No one has any immunity to the microbe because we have never before been exposed. The disease affects us all and rapidly spreads to others because of the density of the population. Clear examples of this are Sub Saharan Africa and India. It does not yet seem to have happened in the Amazon.

• Scientists had also found that there is a polar migration of animals, particularly cold blooded ones; animals move northward as the climate in which they thrive becomes too warm. It is possible that the COVID carrying bats had previously been in a more rural and warmer area and then moved into the Wuhan area due to increasing average temperatures.

• Finally, urban environments with extensive air pollution create more susceptible hosts. Air pollution exacerbates underlying respiratory diseases such as asthma and causes damage to the respiratory system (lungs). 

It has been encouraging to see that there was an upside to COVID in terms of climate change. A major drop in CO2 emissions was noted during the first several months of the pandemic due to decreased use of automobiles and less airplane travel. But this is a short term gain which will reverse, as it did in 2008.

Climate change will continue to occur. Other diseases such as COVID will continue to emerge as the predisposing factors listed above continue. The pandemic will eventually ease but we, as humans, must remain vigilant and do our individual part to minimize these changes.

If you are interested in helping to do this work at a local level, please join Strafford Climate Action. We meet regularly by Zoom and are always looking for new inspiration!