Coronavirus risk increases up the wildlife supply chain
There are a few ways that viruses can jump from animals into humans. But the wildlife trade is still a prime suspect, because as wild animals are caught, shipped along to cities, and served at markets or restaurants, there are a huge number of opportunities for people to catch a coronavirus off the raw meat. And now, scientists at the Wildlife Conservation Society have shown that as you move along this supply chain, the number of animals infected with coronaviruses goes up, increasing the risk for humans as well. Eva Higginbotham spoke with lead researcher Amanda Fine...
Amanda - We looked at the live rodent trade - rodents that are collected by traders then moving through to large markets and to restaurants - to look at the prevalence and also the diversity of coronaviruses. We found significant differences. with traders, trackers, we had about 18% of those samples we tested were positive; and then as we got to large markets where you're bringing in animals from a lot of different sources, we were up to 32.8%. And then at the end consumer, primarily in restaurants, we had just over 50% were positive. What we're seeing is the result of animals with their coronaviruses coming from many different places, mixing, transmission occurring. Many of those animals in the trade chain are stressed and therefore more susceptible to virus, and potentially would shed more virus. As they go further to the end consumer, they're meeting more animals from different populations, and you get more transmission and therefore more samples that are positive when you test.
Eva - So the number of animals that have coronavirus goes up, but what about people?
Amanda - We would expect that the risk of one of those viruses moving from the wildlife to the people, the more there are, the higher the risk. How a human would become infected with a virus very much depends on the kind of contact they have. The more contact you have, the more potential there is for transmission; so definitely handling exposure to the virus in the environment, and direct contact through consumption of the wildlife as well.
Eva - Does that also increase the risk for making a virus that is going to be more of a problem for humans, because you have more mixing of more viruses, in more animals, in close proximity?
Amanda - We definitely think so. In this study, we show that you have an increase in the overall number of these coronaviruses, that is more opportunity for different individual viruses to recombine in an individual or for those to recombine and affect another. So that is the process through which a new virus emerges.
Eva - So it's kind of like a perfect storm for speeding up evolution of these viruses, in a way.
Amanda - Absolutely.