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Professor Wolfgang Preiser is one of South Africa’s leading specialists on zoonotic diseases – those, like Covid-19, that jump from animals to humans. The head of the division of Medical Virology at Stellenbosch University, he is an expert of global standing on zoonotic diseases. When the first SARS outbreak occurred in 2003, Preiser and his medical colleagues were among the first people to isolate the virus. The German-born professor served as an advisor to the World Health Organisation (WHO) on this outbreak. Here, BizNews editor Jackie Cameron talks to the professor about Covid-19, zoonotic diseases and how much of a risk animal-borne diseases are to humans. – Jarryd Neves
Professor Wolfgang Preiser is the head of the division of Medical Virology at the University of Stellenbosch, which is a division of the National Health Laboratory Services. Professor Preiser is a medical virologist with a global reputation and he has undertaken extensive research on the types of diseases that the coronavirus falls into, Professor, let’s just start with a look at Covid-19. What type of disease is it?
It is what we feared would be coming along at some stage. Obviously, we could not predict when exactly. But it is a viral infection that is transmitted quite easily through the air, more or less severe disease. We are still learning about how bad it is. We have learned that many cases are relatively mild, but we’ve also seen – particularly in predisposed patients – that it can be a devastating illness. That’s exactly what we’ve been predicting – to some extent – to happen for quite some time. It is not unlike the much feared and much prepared for influenza pandemic. But it is a different virus, obviously.
Did you say similar to the flu virus?
Logically speaking, coronaviruses and influenza viruses are different. They share certain characteristics but what they have in common is that there is a huge reservoir out there in the animal kingdom. These are both groups of viruses that quite easily change their characteristics and may occasionally become infectious to human beings. If there’s a sufficiently close contact between the source animals and humans, the virus can jump the species barrier and then cause human infection.
That probably happens quite frequently without many people taking notice because many of these infections are mild and many of these viruses will not be easily passed on from human to human. If we are unlucky – as we have been this time – the new virus then has the ability to be spread very efficiently from human to human and cause severe disease, at least in the proportion of those infected.
Then what happens is exactly what we’ve been dreading – a new pandemic. For quite some time we have known that these pandemics do happen and that even though we cannot predict exactly what type of virus is going to cause it – and when – we have known that it is something we need to prepare for. There have been quite some efforts in doing that, starting in the animal reservoirs. Looking at what viruses occurred there, what their characteristics are and how much they would have to change in order to pose a threat to human beings.
But also preparing the health system for such an eventuality. Looking back is maybe a bit premature seeing as the pandemic is still ongoing, but looking at the past nine months in global history, I think we haven’t done very well in either.
This is a virus which was actually more or less found a few years ago in animals. Once it had done that, many countries – including very advanced industrialised countries – found themselves quite unprepared to face the threat.
It’s not a wonderful moment in human history with regards to our ability to put what we know into practice.
Professor, that’s very interesting because the perception is that this disease was only discovered – at best – at the end of last year. But you’re actually saying we’ve known about this for a while and collectively the scientists haven’t done anything to find a solution to it?
I was involved in 2003 with the first SARS outbreak in East Asia. At the time I was working in Frankfurt and we happened to receive through a transcontinental flight, the first SARS patients. In that way also, we happened to be among the first groups to isolate the causative virus. At that stage, it was really a surprise that this was a coronavirus. Coronaviruses have been known for several decades, but haven’t received much attention by human virologists and doctors. The reason being, that the human coronaviruses – prior to this epidemic ones – cause typically mild disease (a common cold-like illness) and are also not very easy to work with in the laboratories. It has very little clinical consequences because we know the patient is going to recover within a week. It doesn’t really make them great targets for scientific efforts.
In 2003, we learned that we were wrong and that we should have taken cues from our veterinary colleagues who had known coronaviruses. I’m talking of different members of the coronavirus family here. In veterinary science, coronaviruses had been known for many years to be the etiologies of very severe diseases. Our veterinary colleagues had really investigated these properly, developed vaccines, diagnostic tests and so on.
Human virology only caught up in 2003 when SARS came along. We caught up quite quickly. We learned a lot. We have since understood that the likely original source of these viruses are bats. With a huge multitude of different coronaviruses living in bats, naturally, and as befits the natural host not known to us causing any ill effects in the natural reservoir. Occasionally these bat viruses may spill over into other mammals, including human beings. That is what happened in 2003 with the original SARS-CoV-1.
It then happened again in 2012 with MERS – the Middle East Respiratory Syndrome – which can infect humans from camels. But then subsequently – particularly if there’s poor infection control in health care settings – human beings can then infect one another. Luckily, neither SARS-CoV-1 nor the MERS coronavirus are very infectious, so they do not transmit that easily. The diseases they cause are quite devastating. The mortality with SARS-CoV-1 was about 10% and with MERS it was 30%. Luckily, both viruses were unable to establish themselves in a human population.
That was the situation until the beginning of this year. Obviously we’ve learned a lot since then. That close relative of the first SARS coronavirus has now emerged again. Being clinically less devastating, but being far more infectious. One of those features is that the patients are infectious prior to developing symptoms. The two days before you fall ill and can be diagnosed and should be isolating yourself, you’re already infectious. So the somehow less dangerous virus actually turns out to be more dangerous in the sense that we were unable to stop its spread through the human population. That is what ended up in the ongoing pandemic of coronavirus.
Just looking at the bigger issue of diseases jumping from animals to humans. How much of a problem is it in our daily lives? What other diseases are we contracting that are zoonotic and we don’t realise it?
There’s a multitude of infections that can be transmitted from animals to humans. In fact, a lot of the problems started when our ancestors started domesticating animals. Obviously, that improved their social and economic situation. They had a more stable food supply and they could settle. But the cost of the close interaction between these different species was that pathogens were traded either way. This is where we think diseases like TB, measles and others came from originally.
So it’s not anything new. It’s happened ever since. Whenever humanity takes another step, there is a risk that we open a new Pandora’s box and expose ourselves to new pathogens. While not new, things like rabies, a number of bacterial infections and parasitic infections all count among the zoonoses. What we are particularly concerned about are those viruses or other agents out there in the natural world with which we normally would not have much contact.
So there’s a forest species and a forest remains undisturbed. That agent/virus would be circulating in its natural host. Of course, we don’t leave them in peace. Also we are far more than we’ve ever been before. Our species has grown to shocking numbers. That means that density and the contact rate between people has also intensified massively. Taking all this together, the chances of such a spillover event happening increases massively.
We were shocked when, in West Africa, the Ebola outbreak not only spread to three countries but actually continued for more than two years. People said, well, they hadn’t known it in these parts of the world, but in the Democratic Republic of Congo, they have known about Ebola since the 1970s and have become very good at controlling it. But look at the outbreak in the Eastern parts of the Congo that also continued for up to two years. Had we not had a vaccine, it would probably still be ongoing. So it’s a very explosive mixture of us interfering more and more with the natural world, often causing changes in an unintended fashion.
I don’t think anybody does that on purpose. But by our intrusion into natural habitats and our interference – often in a destructive way – we are unleashing a whole Pandora’s box of agents that are otherwise sitting there very happily. Our own population density, economic activities and so on come to the fore and do the rest. I’m still quite convinced that many events never make it onto the global stage. There are probably a lot of mild infections happening. But the more you allow this to happen, the higher the chance that one or the other actually becomes a global event. That is what’s happened with the coronavirus. That is also what we have feared for a long time, that this can happen any time with a new strain of the influenza virus.
Are we fairly sure that bats were the primary source of the Covid-19 virus?
Ultimately, I think yes. But whether the virus was able to move from a bat to a human being or whether it went through an intermediary host is unclear. We haven’t worked that out yet. Investigations are ongoing. It’s not clear whether there will be a solution to that riddle. But what we do know – and this is what we found ourselves, studying bats in Southern Africa for the past eight years and what many other people have found in different parts of the world – is that bats harbour a huge variety of different coronaviruses, just like aquatic birds harbour a huge variety of different influenza viruses.
The vast majority of which do not pose a threat to any other species, including our own, but some of which may – if given the opportunity – possibly evolve into a form that may infect us, cause severe disease, be transmitted quite readily from human to human and thus cause the next pandemic. I really want to stress, it’s not a question of blaming bats and doing atrocious and – in most places – illegal things by destroying bats roosts and so on. The country is right. We know that by interfering with animals, you upset population structures and you normally make things worse.
We saw that in Central Europe, where for many years in the last century, people were actually hunting foxes very aggressively to combat rabies. What happens is, if you kill many foxes in a certain area, foxes from outside that area will now move in because there’s now mice in abundance, which may also carry certain infectious agents, so it may not be a good trade in any case. However, you also unsettle the population structure and cause migration. So my plea is to be kind animals, leave them in peace, do not interact with them in a nonsensical way or interact at all, unless you need to.
Rather get an animal handler if you find an injured animal, a wild animal. But don’t be afraid. If left undisturbed, these animals don’t pose a threat to us and they are to have many positive effects. Nevertheless, it is interesting to study the variety of potential pathogens that different types of animals carry, so that we can be better prepared. The next time something happens, we are quicker in developing diagnostic tests and we may also devise preemptive measures. We may be able to say, “This is the time of the year when the bats have their young. This is when there’s a lot of infections being passed among the bat roost, so stay away from it.”
Simple measures that might help. I must say, I am quite saddened to see that despite us and many colleagues around the world accumulating such a wealth of knowledge about coronaviruses in bats and other types of wildlife. Despite the risk factors being quite well known, nothing was done really about it to prevent the consumption and trade of these bats, which is the obvious way of preventing this type of spillover.
What do you think about tracing now? Do you think that will help curb the spread further?
I think it can contribute. I have now also installed the new South African contact tracing app. Within the limitations that these things may have, if a sufficient number of people use it, it will help. In fact, I am currently attending a workshop and one of the intended participants can’t make it. So, we are Zooming him in because he has been diagnosed with Covid.
He is coughing, but otherwise is not doing too badly. But, he does not know where he would have become infected. So the hope is that by more widespread use of these apps, he would have received a warning from somebody that he encountered who at the time, was very likely still feeling perfectly well. Then, a day later came down with a cough and a fever, went to have a test, got the results a day or two later, and then found that he had Covid and exposed others. I think this is where apps can really help. I’m all for it.
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