Interview with physician epidemiologist Menno Bouma

Viruses are like burglars. You have to stop them at the front door.

Physician, epidemiologist and emeritus professor Menno Jan Bouma lived in East for many years. As a guest lecturer he gave lectures at the Tropical Institute in East. He now lives in Ireland, but still likes to come to East regularly. He devoted his life to researching the ecology and spread of viruses and other pathogens. In this time of the coronavirus, I would like to know more about viruses. So I talk to him about that.

Interview |Ruby Tilanus

You worked at the Tropical Institute in London, but came back to teach at our Tropical Institute in East. What was that like?

Terrific. There are only a few places in the world with an enormous amount of knowledge about infectious diseases. The Royal Tropical Institute in East was one of them. Unfortunately, in the 1960s, many thought that we had mastered infectious diseases, and in and after the 1980s, the Tropical Institute was largely cut back. The library has been closed. Specialists, collections and books disappeared. As a result, a lot of knowledge has been lost. And where knowledge is lacking, fear lurks.

That knowledge could now have come in handy in tackling the coronavirus.

Indeed.

Fortunately, you are still here, and you want to share your knowledge about viruses with us. First of all, tell us: what is a virus anyway?

A virus is not a 'living' being like you and I are. A virus does not 'live'.

A virus consists of genetic material (DNA or RNA) surrounded by a package (a shell). Without a 'host' or 'hostess', a virus cannot do anything at all. It's as dead as a piece of plastic. It does not show any sign of life.

But if a virus is lucky enough to penetrate cells of a host's body, it will behave like a bear coming out of hibernation.

The virus uses the building blocks of its host to reproduce itself. That is the only thing a virus can do and a piece of plastic cannot. That is also the only thing that a virus itself, actively, can do: reproduce itself. Although: self, actively... To do this, a virus does need a host.

What happens to a virus after reproducing?

After reproducing, the new, young viruses start looking for a new host.

That's where such a young virus has to travel and penetrate. That is quite difficult for the virus, since it cannot do anything itself, except reproduce itself. He has to travel passively or try to hitch a ride somewhere, and then try to get in somewhere. If that is successful, the virus party of reproduction can take place again. So the virus cycle is: travel, invade, reproduce itself, travel, invade, reproduce itself and so on. A virus cannot or does not do anything else. Because a virus is not 'alive'.

How do viruses do that: passive travel and passive entry? A virus has no wings, no legs and no webbed feet to travel, does it? And a virus can't just enter through your skin, can it?

True! A virus has no wings, no legs and no webbed feet to travel from one host to another. And indeed, a virus cannot just enter through your skin. Your skin is literally an impenetrable barrier for a virus.

Viruses have developed various strategies in the course of evolution, to travel and to be able to penetrate their hosts. The way a virus travels is directly related to the way in which the virus enters the body of its host after its journey. So you always have a way of traveling and a way of entering that are linked to each other. Each virus species specializes in at least one of these strategies. Based on this, you can divide all viruses that exist into roughly three different main groups.

Please tell me a bit more about those different main groups of viruses...!

You can give the main groups the following names:

– 'Opportunists': they enter the body through damage such as a wound or a blood transfusion (think of the AIDS virus);

– 'Survivors': they follow the path of food (think of diarrhoea viruses);

– 'Kites': they hitch a ride with the air that is inhaled (think of flu viruses and corona).

You first mention: Opportunists (such as the AIDS virus). What is the strategy of Opportunists?

An opportunist waits until he finds an opening somewhere in the skin of the new host, a wound for example. Then he waits until his old host makes direct contact with that wound with his blood or with his sperm. And then he enters the body of the new host through that wound. Opportunists can also enter through an insect sting (sting).

And Survivors (such as diarrhoea viruses)? What is their strategy?

Survivors are resistant to the extreme acidic gastric juices and the extreme conditions of the intestines, and can survive there. They reproduce in the intestines. If an old host does not wash his hands after defecating, a minuscule amount of faeces can get on the hands of the old host, and that can then end up on, for example, a table, an elevator button or another surface. If the new host touches that surface, or shakes hands with the old host, the Survivor can land on the hands of the new host. If the new host then licks his fingers and does not wash his hands before eating, the Survivor can enter the stomach and intestines of the new host through the mouth.

Of course, what interests me most in this corona time: what is the strategy of Vliegers (such as flu viruses and corona)?

Kites have a strategy: hitch a ride with small droplets that the old host lets out through the mouth. When the old host exhales, talks, sings or coughs, all kinds of small droplets come out of his mouth. Kites try to hitch a ride with those small droplets. A lucky kite leaves the body of the old host in a small droplet. It then travels through the air to a new host, and enters the body along with the inhaled air. There he tries – still packed in a droplet – to hitch a ride up to the alveoli, deep in the lungs. Deep in the lungs, the lung wall is very thin: only one cell layer thick. Our immune system is weak there: far fewer virus particles are needed to make you sick.

How small are those droplets really?

The droplets are all small. But some droplets are many times smaller than other droplets. The smallest droplets are called 'aerosols' and they can fly.

Fromlarger dropsdo not float in the air for long. They fall to the ground within a few seconds due to gravity. They cover a distance of about half a meter when breathing normally to a few meters when coughing vigorously. To reach the new host, the Kites must be at nose or mouth height of the new host. However, the larger droplets soon bend towards Earth due to gravity. Theaerosolsfloat in the air for a very long time. If there is no proper ventilation, they can continue to circulate in the air for hours. They can travel enormous distances.

Okay, this is the story from the side of the viruses. But what about our side of the story? What is our defense against viruses?

Humans have been living with viruses since their inception. We and our distant ancestors in the animal kingdom have evolved together with the viruses, as it were. There are many forms of innate and acquirable defenses that have developed over time. Antibodies are just one of them. For each of the different strategies of viruses for survival (Opportunists, Survivors and Flyers) we have developed appropriate defense strategies.

Tell us: what is our defense strategy against Opportunists (such as the AIDS virus)?

Our oldest defense may have been developed against Opportunists. We have a skin. Our skin stops almost everything harmful that wants to penetrate our body. If we have a wound, our body is very capable of healing that wound very quickly.

And what is our defense strategy against Survivors (such as diarrhoea viruses)?

For them, we have developed an incredibly acidic stomach, among other things. Our gastric juice damages almost all viruses, so that they can no longer reproduce. Most Survivors don't survive our gastric juice either – only the few who do get the chance to reproduce.

And now the most important thing: what about our defense against Flyers (such as flu viruses and corona)?

To get deep into the lungs, a Kite must first pass through the mouth or nose. We all have several defense mechanisms in our nose and in our mouth and throat, including immune cells. An entire army with a vanguard, a rearguard and many layers of commanders is ready to stop the Flyers.

Most intruders get stuck in the labyrinth of mucous membranes and small hairs in your nose and are rendered harmless here. The mouth and throat also participate in the defense against the Flyers. If they do end up in the stomach, they don't stand a chance there.

Does it matter whether a Kite enters via a large or a small droplet (aerosol)?

Yes. If a Kite hitches a ride with a small droplet (aerosol), the chance that it will break right through the defense line is much greater than with a large droplet. Just like small fish have a much greater chance of slipping through the meshes of a net than large fish. Together with the inhaled air, the Kite can also – if he is lucky – fly deep into the lungs. After all, the droplet is so small that – with a bit of luck – it can go directly into the lungs. The Kite virus then hitches a ride with the aerosol.

If a Kite hitches a ride in a large droplet, it has a much harder time when the new host enters. The chance that he will be stopped at the gate (in the nose, mouth or throat) is then maximum.

What exactly happens in the nose?

Everything in the nose is aimed at preventing viruses, bacteria and other germs from entering our body. In addition to the nose, the mouth and throat are also extremely adept at this. Our immune system is ready to deal with intruders. In most cases, we succeed in effectively stopping intruders (such as viruses and bacteria) in the nose and making them harmless. In the meantime, we have 'met' the intruder. This means that the next time the same intruder shows up at our front door again, we can intervene all the faster and more effectively. You can compare that to a kind of standing and getting acquainted at the front door: our body is introduced to the hitherto unknown virus, and can start to build up defenses and make antibodies against the virus.

You have researched the role of the seasons and the weather on the spread of infectious diseases. Does that also play a role in the spread of corona?

Yes, most infectious diseases are seasonal diseases. For Vliegers, this is mainly due to temperature and humidity. Flyers such as flu viruses and corona thrive in cool, dry air, while Survivors dehydrate and die faster in dry air. It is not yet entirely clear whether the humidity is bad for the virus itself, or for the lifespan of the aerosol. In humid air, aerosols may deflect quickly towards the earth. In dry air, aerosols can continue to circulate much longer. In the summer, we have seen many corona cases worldwide in the meat processing industry: there, the air is kept cool and dry and, to save costs, it is insufficiently refreshed with outside air: a 'Valhalla' for Flyers (aerosols). In the winter, we heat our homes and spend more time indoors. The air dries out and we live together in a smaller space. You can then ingest a larger dose of viruses into the lungs, your most vulnerable spot. That makes flu and corona real winter viruses. Savings on heating (from draught protection to intelligent systems that only supply fresh air when it is really needed) usually come at the expense of fresh and more humid outdoor air. So we have to be careful with that!

With the winter season approaching, I advise everyone to ensure good humidity in the house. By putting a bowl of water on several radiators, for example.

Do you think it is wise to meet people outside?

Meeting outside is indeed wise. The behaviour of aerosols can be compared to the behaviour of cigarette smoke. If you smoke a cigarette outside, your smoke evaporates quickly and others are not bothered by it, except when you blow them in the face. It is the same with aerosols. If you carry the coronavirus and you meet people outside, they will not be bothered by your aerosols. Except when you blow them in the face.

And what exactly about ventilation? Does that make sense?

Yes, that certainly makes sense. Compare it again with cigarette smoke. If you go to smoke a cigarette in my living room and I don't ventilate well, well, I can still smell your cigarette days later. But if I open the windows opposite each other for a while, the smell disappears in no time.

It is the same with aerosols. If you ventilate well and open the windows against each other, they will be gone in no time. Especially in winter, the peak season for the virus, fresh air is very important.

What else can we do to contain Kites like the coronavirus?

Very important in the fight against all infectious diseases is: make sure that your natural immune system can function properly. Think of healthy food, sufficient exercise and sufficient sleep. To strengthen your body, take an extra dose of vitamins C and D every day: these vitamins help your immune system.

Also take care of psychological well-being. We call this 'vitamin P' where the P stands for pleasure. Do things that make you happy. Dance, make music, meet up with friends, go out.

And always avoid super spread events.

Why superspread events? Tell us more about that...

The coronavirus can spread super fast during so-called 'superspread events'. These are events in which many people are together for hours in a poorly ventilated room. Think, for example, of après-ski bars or carnival cafes. Only one person needs to carry the coronavirus. That one person blows many aerosols into the air unnoticed. Probably some coronavirus carriers do this more intensely than others. All those present then inhale these aerosols for hours. The virus has a very good chance of penetrating many people, in numbers that our immune system cannot handle.

I don't hear you talking about washing hands, disinfecting, keeping your distance, not shaking hands, and not hugging...!

These measures are perfect for tackling Survivors such as diarrhoea viruses. Survivors travel from host to host through hands, through surfaces and through touch. If you want to tackle these viruses, it is indeed very good to disinfect everything and to keep your distance and not touch each other.

But now we know that corona is a Kite. Kites have a different strategy for traveling from host to host, and for invading hosts.

As said: Kites spread mainly through the air. Compare it again with cigarette smoke: it spreads little or not at all through hands or surfaces. Just go and blow cigarette smoke against your hands, and then shake hands or hug someone else. The chance that your cigarette smoke will end up deep in the lungs of the other person in this way is minimal. Kites need a lift from aerosols, in order to be able to get deep into the lungs where our body has less resistance. The measures to wash hands, disinfect, keep your distance, do not shake hands and do not hug are therefore hardly effective when you want to tackle Flyers such as flu viruses or corona.

But Menno, that goes directly against what Mark Rutte asks of us, doesn't it?!

Partly yes. But Rutte has also asked us several times to use our common sense...

I've heard you say: 'Viruses are like burglars. You have to stop them at the front door.' What exactly do you mean by that?

There is a big difference between a burglar who is stopped at the front door, and a burglar who enters your house for a while and then moves out again, and a burglar who settles in your house and lives there. It is the same with viruses. If you stop a virus at the front door, or if you stop a virus in your nose, mouth and throat and make it harmless there, then you are doing well. You literally get to know the virus up close, so that you can react even faster next time. If you inhale a virus for a while and then breathe it out again, there is not much to worry about. But if a virus settles deep in your lungs and starts reproducing there, yes, it can make you very sick.

We are currently seeing a huge increase in the number of corona infections. Also here in East. How do you feel about that?

The infections are now measured with the so-called 'PCR test'. This test examines whether you have the coronavirus in your nose, mouth or throat or remnants of the dead virus if the infection has already passed. Many people who have the virus in their nose, mouth or throat are busy 'getting to know each other and stopping at the front door'. As I just said: in normally healthy people with a normal immune system, there is a whole army of immune cells ready in your nose, mouth and throat. That army gets to know the virus, makes the virus harmless, and at the same time has learned about the virus and so it can react even better next time. I personally think that the word 'infection' is therefore not so well chosen. I would prefer to speak of 'acquaintance'. Yes, it is true that the number of 'acquaintances' with the virus is increasing (enormously).

But isn't it very bad that the virus is in the nose of more and more people?

Yes and no. People who have learned about the virus and managed to stop at the front door function as a kind of 'living shield' for all vulnerable people in our society. I am talking about the famous 'herd immunity'. As a community, you need some time to build up herd immunity. Young, vital people are generally not or hardly affected by corona. For them, it almost always remains with a little sniffling. In the Netherlands, the sense of togetherness is great, and the care for the elderly is wonderful. A nice slogan could be: 'Take good care of your grandmother: make sure you have had corona.' The more young, vital people have become acquainted with the coronavirus and have stopped the virus at the front door, in other words: have become immune to corona, the more beneficial that is for our fellow human beings with a very weak immune system.

That brings me to the question: how deadly is corona really? Do virologists and epidemiologists have a standard yardstick for this?

In the Netherlands, there are 17 million people. Every day people are born, and every day people die. That is a natural process. If more people die than average, we speak of 'over-mortality'. If fewer people die than average, we speak of 'under-mortality'. In the Netherlands, we had excess mortality in the months of March and April 2020. After that, there was a months-long period of under-mortality in our country.

We express the lethality of a virus with the IFR, the Infection Fatality Rate. That is the percentage of people who have been in contact with the virus who die from the virus. Corona has an estimated IFR of 0.5 percent or lower. This can be compared to the IFR of a medium to severe flu.

Yes, corona is a new virus. But I want to argue for moving from fear to trust. We count the brothers and sisters of the coronavirus under our 'medium winter flu'. There is no need for global panic. People generally deal with the much more serious infections that you see in the tropics much more rationally.

But in the US, a lot of people die of corona, don't they?

True. In areas with a high mortality rate, it is striking that it is mainly the socially deprived part of the population that dies. This part of the population has an increased risk for a serious course of the disease, such as obesity and diabetes. Bad food, bad air, bad housing, poor (clean) water supplies all contribute directly or indirectly to a weakened immune system.

At the moment there is a lot of fuss about face masks in schools. What is your opinion on that?

Perhaps face masks can help somewhat to prevent you from passing on the virus to others if you have the COVID-19 disease. In schools, however, the advantages seem to be smaller than the disadvantages: risk of shortness of breath, concentration problems, headaches and perhaps brain damage.

How do you think corona will continue in the coming months and years?

It is to be expected that we will have an increased risk of aerosols in the months of November to April. If we protect the vulnerable in society well, and if we ventilate well, the second wave will not be as severe as the first wave. After all, many people have already become acquainted with the virus. In the future, corona will continue to come back in the winter months. But it never has to be as severe as it was last spring, when the virus was completely new to everyone.

You have dedicated your life to studying the approach to infectious diseases. What do you notice worldwide in the approach to the coronavirus?

The cuts in care and the slimming down of the hospital bed stock has contributed significantly to the fear and panic measures to prevent us from being overwhelmed by the volume of patients. Unfortunately, this does not only apply to Amsterdam East and the Netherlands.

Unfortunately, because the benefits of austerity are often not evenly distributed, a large part of the world's population has become even more vulnerable in terms of following a healthy lifestyle.

As far as the approach is concerned, I think that a study of the older literature and targeted research on the basis of this can contribute to an effective policy. A policy stripped of fear, panic and the need to sacrifice personal freedoms.

Robijn Tilanus is improvisatiecoach en componiste. Daarnaast schrijft ze als freelance journalist voor oost-online over onderwerpen die haar raken: natuur, muziek, gezondheid en markante mensen met een missie.

Thanks to https://oost-online.nl/