Viral Spillover Risk: Meaning and how it could lead to new Pandemics?

Context

Recently, proceedings of the Royal Society B, the biological research journal of the UK’s The Royal Society, published a new research that climate change in the High Arctic lake sediments, increases the Viral spillover risk.

Probable Question

According to new research, yet another effect could be the increased risk of “viral spillover” in some regions that could cause new pandemics over the next few years. Comment.

About Spillover

• It is also known as pathogen spillover and spillover event.
• When a reservoir population with a high pathogen prevalence comes into contact with a novel host population,spillover occurs.  
• The pathogen is transmitted from the reservoir population and may or may not be transmitted within the host population. 
• Due to climate change and land use expansion, the risk of viral spillover is predicted to significantly increase.
• Spillover is in fact, more than 2/3rd of human viruses are zoonotic. 
• Most spillover events result in self-limited cases with no further human to human transmission, as occurs, for example, with rabies, anthrax, histoplasmosis or hidatidosis. 
• Other zoonotic pathogens are able to be transmitted by humans to produce secondary cases and even to establish limited chains of transmission. 
• Some examples are the Ebola and Marburg filoviruses, the MERS and SARS coronaviruses or some avian flu viruses. 
• Few spillover events can also results in the final adaptation of the microbe to the humans, a new stable reservoir, as occurred with the HIV virus resulting in the AIDS epidemic.

Also read: What are Satellite Phones?

About Viral Spillover

• Viruses are some of the most abundant entities on earth, but they need to infect a host’s cell in order to replicate. 
• According to the research, these virus/host relationships seem relatively stable within superkingdoms, the major groupings of organisms. 
• However, below this rank, viruses may infect a new host from a reservoir host (in which it usually resides) by being able to transmit sustainably in a novel host, a process that is defined as ‘viral spillover’.

The New Research

• To study the possibility of a viral spillover, researchers from the University of Ottawa collected sediment and soil samples from Lake Hazen in Canada.
• Lake Hazen is the largest High Arctic lake by volume in the world, and the region’s largest freshwater ecosystem.
• Then they undertook DNA and RNA sequencing to reconstruct the lake area’s virus composition. 
• They estimated the spillover risk and found that the chances of a virus moving to a new host increases with runoff from glacier melt, treated by them as a proxy for climate change. 
• As temperatures increase, the melting of glaciers increases as well, and there is a greater possibility for previously ice-trapped viruses and bacteria to find new hosts.

Effects of Climate Change

• The effects of climate change range are being witnessed across a range of environments from changes in crop yields due to unreliable weather conditions to the extinction of species. 
• Climate change could shift the species range of certain viral vectors and reservoirs northwards, and the High Arctic zone could become fertile ground for emerging pandemics.
• Climate change also leads to shifts in new associations that can emerge, bringing in vectors that can mediate viral spillovers.

Outcome of the Study

• The risk of viral spillovers increases with changes in the environment at a particular location, driven by global warming.
• This does not guarantee a higher possibility of a pandemic occurring via viruses here. 
• The study provides a novel approach to assessing spillover risk.
• However this is not the same as predicting spillovers or even pandemics because there is another important link in the process. 
• As long as viruses and their ‘bridge vectors’ acts as hosts and lead to their spread are not simultaneously present in the environment, the likelihood of dramatic events probably remains low. 
• However, that also does not signal relief. 

News Source: The Indian Express

https://indianexpress.com/article/explained/explained-sci-tech/what-viral-spillover-risk-means-how-it-could-lead-to-new-pandemics-8223753/

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