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  • Writer's pictureDr. Ursula Pomeroy-Arthur

The Dark Side of Disease Eradication: Hidden Complexities and Pandemic Preparedness




Following the Covid-19 pandemic, extensive efforts have been made in the way of pandemic preparedness. At some point since then, most of us have heard that we will likely see another pandemic within our lifetimes.


The vast amount of research and funding in the biotech industry to produce vaccine pipelines and therapeutics should give us some comfort in the hopes of disease eradication. With our eyes now so widely open, why is it that we should still be worried?


 

The Red Queen Hypothesis


It is estimated that 75% of infectious diseases emerging into humans originate in animals ¹. Factors such as human activity in wildlife habitats, intensive farming, illegal wildlife trade, and consumption of wild animal meat has resulted in the emergence of new pathogens over recent years ².


When a disease-causing pathogen has been dealt with and eradicated, it is of course cause for celebration. However, the absence of this pathogen means that a ‘niche’ or space has been created in the ecosystem for another pathogen to take over. With some critical mutational changes, a pathogen can evolve and adapt to infect new host species.


This has been likened to the ‘Red Queen’ hypothesis created by Leigh Van Halen, inspired by the story of Alice In Wonderland. In the story, Alice finds herself in a race with the Red Queen. Despite running as fast as she can, she stays in the same place. This hypothesis describes how a species must constantly evolve to keep up with their enemy ³.


In this instance, humans are quickly tackling disease, but pathogens evolve so they can keep up.  Pandemic preparedness is the action station we take to be ready for this event inevitably occurring.


 

Of Monkeys and Men


Let’s take the example of Smallpox. The Variola virus which caused Smallpox was declared globally eradicated in 1980 by mass-vaccination of people. This was a huge success and undoubtedly saved millions of lives worldwide. In recent months the Monkeypox virus has been increasingly observed in human hosts.


Monkeypox was first diagnosed in the Democratic Republic of Congo in 1970, with sporadic outbreaks occurring solely in people who had direct contact with wildlife reservoirs of the disease ⁴. This was evidence that the virus could infect people opportunistically, when they came into close contact with the source, and person-person spread was limited, meaning that the virus was not yet able to efficiently infect humans ⁴.


The absence of Smallpox in the environment created a niche for a similar, related virus to take over and emerge fully into humans. With evidence that Monkeypox could already opportunistically infect humans by undergoing a series of amino acid mutations, it makes sense that this virus has since adapted to infect more efficiently and rapidly between humans. Since May 2022 there are approximately 300,000 reported cases globally, although this figure is likely to be underestimated ⁴.

 


 

Peste Control


We have all learned of the impact that emerging diseases can have on humans in the last four years, but disease emergence is also increasing in animals. For thousands of years, the Rinderpest virus of cattle devastated livelihoods of people across Europe, Africa, Asia, and the Middle East ⁵. With the advancement of international trade, the disease spread around the globe and had a mortality rate of 80-90% ⁶. The saviour of this economic burden was the Global Rinderpest Eradication Program, which declared the disease officially eradicated in 2011; a saving grace for millions of people in the livestock industry.


This, however, created a niche for a similar virus to take advantage of the situation, such as Peste des Petits Ruminants virus (PPRV). Traditionally a deadly disease of sheep and goats, there is a wealth of evidence which shows the virus can now infect cattle without symptoms ⁷.


The jury is out on whether this will cause complications in the battle for PPRV eradication, but it serves as an example of how viruses evolve to take advantage of a vacant host.


 

A Measley Situation


As we move forwards as a society, the World Health Organisation aims to eradicate the measles virus. This would be a significant milestone, as measles caused approximately 2.6 million deaths globally each year before the widespread vaccine was rolled out in 1963. Eradicating the disease would, of course, be a good thing for humans.


The running theme here is that there is always a caveat to be aware of when dealing with viruses. Measles is related to the Canine Distemper Virus (CDV), which sounds like it only infects dogs. In actual fact, CDV has evolved to readily infect species across the animal world including non-human primates, our closest relatives. The connection here is that the measles vaccine offers some protection against CDV, shown in many studies on macaques ⁸.


This is because the two viruses are closely related, so the antibodies produced against one can offer some protection against the other. If we eradicate measles, it raises the issue of a niche being created for a similar virus to take over. Considering the genetic similarities between measles and CDV, it is entirely possible that CDV could eventually move into humans.


 

Conclusion


These examples show the importance of pandemic preparedness and need for industries to come up with contingency plans and work together so that we can tackle emerging threats to our health. Vaccines are wonderful, but thanks to evolution, this is the dark side of disease eradication.


It is imperative for key players in the biotech, medtech, agriculture and food sectors to work together to give us the best chance of preventing the next pandemic. That is why I am committed to ensuring the best people deliver on their operational strategic goals in these sectors. From animals to people, having an impact on the future of global health is truly my passion. 


If you would like to chat more about this, you can reach out to me at ursula@cranmoreltd.com. You can also read more about this topic in my PhD thesis, available upon request.



References

1.         Cleaveland et al, 2007. Cons. Biol. 21(3), 612-622.

2.         Tenorio et al, 2022. J. Live. Dis. 13, 76-79.

3.         Van Halen, 1977. The Amer. J. 111(980).

4.         Thornhill et al, 2022. New. Eng. J. Med.

5.         Pastoret et al, 2006. Virus Pla. Lar. Sm. Rum. VI, 86-104.

6.         Barrett & Rossiter, 1999. Adv. Virus Res. 53, 89-110.

7.         Pomeroy-Arthur, 2023. PhD Thesis.

8.         De Vries et al, 2017. PLoS Path. 13(5).




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