In the past, coronaviruses that circulated in humans caused only mild infections. This changed in 2002, when the SARS-CoV virus presented itself in humans as the disease we now know as SARS. In 2020, SARS-CoV-2–a relative of the same virus–has presented itself in humans in the disease we now call COVID-19.
Bernard Bett leads research on neglected and emerging infectious diseases at the International Livestock Research Institute as part of the research portfolio under the Improving Human Health flagship. His studies of zoonoses–diseases that are transmissible between animals and humans–informed the UNEP Frontiers 2016 Report and drew attention to the issue that now concerns just about everyone. In this interview, Bett discusses the delicate relationship between humans, wildlife and the pathogens that circulate among them.
COVID-19 seems to have caught much of the world by surprise. What is your reaction?
I’m not surprised by its emergence. Many emerging diseases have been reported in the last 10 years but we haven’t seen anything like COVID-19, which has affected nearly every country in the world. What is surprising is the rapid spread of this virus across the world.
Zoonotic diseases seem to occur more frequently than before. Why is this?
Zoonotic diseases are increasing. A review of the global trends of emerging infectious diseases since 1940 confirms that their outbreaks have been increasing with time. About 60 per cent of these diseases are zoonotic and slightly over 70 per cent of the zoonotic infections are caused by pathogens that originate in wildlife. Some of the reasons why the frequency of the diseases is increasing is because of the increased close contacts between wildlife and humans, encroachments of lands, urbanization and socio-economic development. As the human population increases and economies develop, the demand for food and other goods increases. Industries like agriculture are intensified. Land use, climate change, economic development, population growth and people living in densely populated areas are all contributors for zoonotic emergence, making it easy for diseases to spill over from animals to humans.
Can you break that down? Exactly how do pathogens merge?
Emerging diseases occur due to changes in the biological structure of a pathogen, the ability of hosts to resist infection and/or the ability of environment to control outbreaks.
A virus that might be harmless today could evolve into a much more pathogenic form, either through genetic mutations or recombination with other organisms that carry critical pathogenic traits. Small mutations often occur as viruses multiply, or as a mechanism to enable these viruses to survive better in their hosts. Read more…
