ویروس کرونا - حیات وحش و بیماری انسانی

This is another in our series of coronavirus episodes of Scientific American’s Science Talk, posted on March 19, 2020. I’m Steve Mirsky.

In early March, the prime minister of Vietnam directed the government to draft a directive to prohibit wildlife trade and consumption, to be submitted to him by April 1, 2020. In February China took similar actions.

To find out more about the wildlife trade and its relationship to the current coronavirus outbreak, I called Christian Walzer. He’s the executive director of global health at the Wildlife Conservation Society. We both live in the Bronx, but due to the current situation, we spoke by phone.

Tell me about the situation in Vietnam where the wildlife outdoor markets or wildlife markets for food consumption are apparently going to be banned and what’s the situation elsewhere, where such markets have traditionally existed?

Yes of these markets which are really very unique, even on a global scale just by the sheer size and diversity of species, which are traded each markets have already been bands beginning of February in China.

So this can opponent ban on any kind wildlife trade BH for consumption medicine focuses even prefers any any kind while electronics is prohibits that most of the movement trade sale and consumption is temporarily abandoned, China has moved on to now permanently band any wildlife trade and related with consumption, so that was the big first step and down there working on legislation right now to get lockdowns, and then Vietnam just followed a few days ago with a statement that they were similarly close down markets and the trade of wildlife related to consumption, and we do assume that it will be a knock on effect on on the bordering countries like Lows and Cambodia.

And what is the problem with these markets? Why are we so concerned about it?

So this markets are Just a quick picture so you can imagine what they look like. It is areas where a large number of different species from rats and any other different species of filed rats what they call field rats in Southeast Asia studies a larger rat species which they which they capture and breed on farms, together with bats, squirrels, porcupines mean a non-elite illegal and pangolin illegal primates and then all that is mixed together with domestic livestock so you have a lot of poultry.

There you will have pigs and then of course you have a lot of humans and I’m putting all the species together and you know that there also, additionally extremely stressed and captured many of them recaptured in the wild are in terrible conditions, holding conditions, severe stress and shutting viruses in the experiment able to excrete these viruses on the imaginary stacked on top of each other, so you will have excessive squirrels excreting virus which will drop down onto a porcupine below them and that porcupines may be above some chickens and so on.

So you have great possibility for the exchange of virus in viral components and then you have the whole processes preparing the food so you actually in the same place where you basically creating the environment for new viruses. You’re also going to be slaughtering so you will have blood mixed, you will be handing that off to humans who will be in direct contact with the expense of the blood, possibly none will take that product.

So it is really you really couldn’t design spillover interface in any better way than this. This is the main concern. Large diversity of species is obviously unknown viruses which they naturally host being mixed together under small tight area.

And they use the word spillover that has a particular meaning in this context right?

Right a spillover event, you have to say, I think the best way to imagine his you know Each animal is a container and within that container it it carries and hosts viruses and bacteria and fungi, which are to not cause it anyhow and similarly we as humans, we host viruses and bacteria, which do not cause any harm.

And as we move about which carries with this this when these containers are able to share these viruses. So basically you get a virus moving from one container, let’s say some wildlife species moving into the container of the human and then sometimes and it’s a rare event, these viruses can actually move that safe from something that looks a bit very different a porcupine definitely different in human can move across into human action get into us human self and start to replicate and then on a much much rarer occurrence. Thankfully, then transmitted from human to human first-quarter achievement for a viruses estate actually managed to jump from one species to the other and then actually be able to transmit within this new species.

But it’s sort of a slot machine with the a lot of the dials and every once in a while they all come up and you do get this event.

exactly it’s really a numbers game and I think this the way I would see these markets are just increasing your chance of avoiding substantive losing in this case just pipe you know having a lot of species on every day of the year, you’re actually stressing them so that you will get more what viral shedding, and then you you put in the humans in as well because consumption of course increases the interface because you as a city in contact with the blood you’re ingesting it’s it’s really just a numbers game as I said.

why do you think this particular coronavirus outbreak has had such a dramatic effect on policy because we’ve had other coronavirus outbreaks, we have had the ever present threat of flu where these markets would serve a similar kind of role in the transmission of a possible new flu variation.

So what’s what’s different now, other than the obvious in all millions of people are being affected?

So the main issue with these spillover events is there unpredictability. So with flu which is no when it gets cold in late fall, the influence of cases, riots of our medical systems and infrastructures prepared for that. When a spillover event happens like this new coronavirus it’s completely unpredictable where it’s going to go how how infectious it. What’s the you know the community attack level.

What are the clinical symptoms how much resource are you going to need to treat the population, and so on… And this is Unprotected predictability, which is always so difficult for society at large base to grasp and to react to and I think this is because of this is the main reason for the, the economic downturn the very divergent responses to this virus and at least in the first few weeks and that is causing me. The anxiety is with no one is particularly anxious about the flu.

So I think we really saw it that West Nile outbreak some time ago a really conscious and for the first time and in my memory anyway. A conscious working arrangement between physicians and veterinarians and animal researchers, wildlife researchers and do you think that’s the case and and why is it so important that the lines of communication are open between traditional physicians who treat humans and other doctors who treat animals.

So you know what is known as the one health approach in its real meaning, that means working together amongst human animal and environmental health while also integrating social, economic, social, cultural and basic the social sciences into the mix is really really essential in this type of outbreak and the collaborations ongoing really demonstrate how well that is work in this the virologist has come from the animal health side of wildlife self outside who are you know I’m sharing massive amounts of data on coronavirus is collected in the past 10 to 15 years, you have the wildlife veterinarians throughout sampling markets.

You have the human and veterinary epidemiologists working on the Howie disease progresses in the dynamics and then obesity on therapeutic society as shipment helps addressing the clinical disease there is. This is outbreak really shows how important it is to integrate the main reason is the actual outbreak in spillover event is driven by enough with ecological and market factors. So if you just looked at it from human health perspective. Once the virus is in human population wouldn’t miss really really important factor in this outbreak and its progression.

So we need to address this together in a multidisciplinary way and it is really heartening to see that is working very very well at the moment.

That’s it for the Seventh Circuit or science news at our website www.scientificamerican.com, the latest news and insights about the coronavirus outbreak, all of which is available free and as always there’s other science news on the site for your edification and enjoyment. Follow us on Twitter will get a tweet whenever new elements of website twitter name is@M scientific American science talk, I’m Steve Mirsky. Thanks for clicking on us.