Zoonosis, and Immune Function

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“Our ability to mitigate disease emergence is undermined by our poor understanding of the diversity and ecology of viral threats.”

Whilst the burden of non-communicable disease (NCD) dominates health and disease globally, its progress through the population is slow, providing opportunity to intervene, reverse and restore health in many cases.

Infectious disease rarely provides such a time related opportunity and depending on a variety of factors can induce rapid local, national or as we have all seen international responses, that we would never see regarding NCDs. For most of us, witnessing the political, economic and societal strains brought about by this recent event can promulgate anxiety, and varying opinions. Yet zoonotic infections on a global scale have been predicted for many years by infectious disease specialists (which has included Disease X), but mostly ignored by governments and the public.

Disease X

Disease X said the WHO in 2018 would be caused by a pathogen never seen in humans, would emerge from animals somewhere in a part of the world where people had encroached on wildlife habitats. Would be more deadly than seasonal influenza but would spread just as easily between people. By hitching rides on travel and trade networks, it would journey beyond its continent of origin within weeks of its emergence. It would cause the world’s next big pandemic and leave economic and social devastation in its wake. (sound familiar?)

Sars-Cov-2 will not be the last zoonotic event (think Disease Y and Z…), and whilst we look to our political leaders to operate planning for such experiences on a national and international scale, we are still required to mitigate the virus risk at a personal level.


Sars-Cov-2 is a zoonotic virus, one of some 25 viral families that emerge from their animal reservoir and through various engagements find a home in other animals and sometimes our human cells. Some create mayhem, others co adapt and most simply discover that there is no future in their new host and die out. These spillovers are increasing exponentially as our voracious ecological footprint brings us closer to wildlife in remote areas and the subsequent wildlife trade brings these animals into urban centres.

It is the unprecedented roadbuilding, deforestation, land clearing and agricultural development, as well as globalised travel and trade taking place internationally that make us supremely susceptible to exposure to pathogens like coronaviruses. Their subsequent impact on our survival is then mediated by a variety of factors, the top of which is an effective immune response.

Almost two-thirds of human diseases originate in animals. Measles, first described in the ninth century, is thought to have come from cattle. HIV most likely leapt into our world via monkeys and apes in the 20th century. The most terrifying epidemics of the past generation—West Nile virus, SARS, MERS, and Ebola all began when an animal pathogen found its way into a human.

By one estimate, 1.6 million animal viruses are yet to be discovered in mammal and bird populations, and there is currently no way to focus in on the estimated 827,000 of them that could cause disease in humans. For a century, approximately two new viruses per year have spilled from their natural hosts into humans.

The first thing to understand is that whatever future threats we are going to face already exist; they are currently circulating in wildlife. Think of it as viral dark matter. A large pool of viruses are circulating and we are unaware of them until we see a spillover event and people fall ill.

As explained by numerous commentators, the disturbances in their environments that create spillover risk are created by us. We have penetrated deeper into ecozones we have not occupied before.

EcoHealth Alliance, an NGO, and others, have looked at all reported outbreaks since 1940. They concluded that there is an elevation of spillover events, two to three times more than seen 40 years earlier. That continues to increase, driven by the huge increase in the human population and our related expansion into wildlife areas. The single biggest predictor of spillover events is land-use change—more land going to agriculture and more specifically to livestock production.

Science, Policy and Conspiracy

As this frequency of occurrence increases there is a tendency, from politicians to the public, to treat pandemics as a ‘disaster-response’ issue: We wait for them to happen and hope a vaccine or drug (with all of their associated risks and complications) can be developed quickly in their aftermath. But even as Covid-19 continues to expand its footprint (over 40 million cases), there still is no vaccine available for the SARS virus of 2002-3, nor for HIV/AIDS or Zika or a host of emerging pathogens.

The virus behind Covid-19 has also become the centre of conspiracy theories, some of them promoted by political leaders. These theories include the contention that the virus was not part of a natural spillover, but a bioweapon created in a Chinese lab. On April 30, the U.S. Office of the Director of National Intelligence tried to put the matter to rest: Still, politicians continued to express suspicion toward scientists in Wuhan, China, where the pandemic originated.

Whilst the development of scientific rationale is based in challenge and test, this normally takes place in the academic environs more used to the questioning of data than the average politician, driven at times by the fear of loss of political authority, rather than the progress of scientific clarity.

Our personal choices

Therefore the recent production of nutrition focussed reviews and studies on the role of vitamins, minerals, fatty acids, foods and bacteria on the generation and support of the immune system, whilst late to the story, represent a material shift from reaction to prevention.

Age appears to be a defining risk factor for adverse responses to Sars-Cov-2 and age associated nutrient deficiency is well known. It appears that whilst there is a reduction in immune cell generation as we age, there are lifestyle changes, from food choice, exercise, sleep, stress management and nutrient supplementation that can restore immune capability to that of someone many years younger.

Whilst we may feel that stopping significant environmental insults is outside of our easy mitigation, lifestyle management for most remains in the realm of ‘possible’ – let’s promote this to family, friends and patients as much as the other mediating proposals are being, and generate a healthier outcome.

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