No time? Short version at the end of the article!

Joël Mossong, you are an expert in modelling the spread of viruses. A very direct question right at the beginning: how long will this situation last here in Luxembourg?

That is difficult to say. It’s a new virus and there are new developments every day. We have to learn that we cannot make long-term plans and forecasts in the current situation and that we have to re-evaluate them from day to day, from week to week. At the same time it is important to inform people transparently and honestly. If I were now to give an estimate, despite all the uncertainties, I would say that this situation must be maintained in this way for at least another six to twelve weeks. It would not surprise me either if the schools were to remain closed until the summer holidays. That is certainly a possible and perhaps necessary scenario. But there could also be positive surprises - and then everything could go faster.

What would those positive surprises be?

For example, the rapid discovery of a vaccine. Usually, this takes time. I estimate three to six months would be realistic. But maybe a vaccine will be available earlier – that is however not very likely. Or researchers may discover that an already approved or new drug has a prophylactic effect, as it was the case with swine flu. For the flu, for example, the drug Tamiflu can be given as a preventive measure, which is particularly appropriate for older people in CIPAs and people with risk factors. This would particularly help to reduce the crowds in the clinics.

So many months of near standstill... The question arises whether it could not somehow get resolved faster? What if the virus could just be spread in an unlimited way?

Or a similar argument: According to some experts (and also according to the German Chancellor) about 70% of the population will be infected with the virus sooner or later. From then on, society would be sufficiently immunised and the virus would be under control. So why shouldn't the virus simply spread quickly so that we can get to this point faster - and the spook is over?

That would be catastrophic! You can quickly work it out. In that case, some 450 000 people would be infected in Luxembourg within a short space of time, three to six months. If one assumes a mortality rate of 1%, about 4,500 people would die of Covid-19 in this period. This is close to the number of people who normally die in Luxembourg over the course of one year. In addition, the health system could collapse - because one would have to expect a few thousand people who would need intensive medical care within a short period of time. Even though Luxembourg is currently working hard to organise more beds, breathing apparatuses etc: that would be just too many patients. A terrible scenario. Doctors would probably have to decide who to admit and who not to admit (which, by the way, is currently the case in Bergamo, Italy). The selection criterion is determined by who has the best chance of survival - that is, people with other complications or chronic diseases would risk not being able to be treated. But, very importantly: we are not yet on this path! Decision-makers and politicians in Luxembourg and Europe have reacted quickly and very far-reaching measures have been taken.

Do you think that Luxembourg has reacted well?

Yes, I think that our government and other key decision-makers reacted very quickly. And I am positively impressed with how well people are reacting to the situation. Surely there are still some who do not follow all restrictions. But many have understood the gravity of the situation and that everything depends on how we act now. It is impressive to see that we have built up a system here in an extremely short time that is almost as restrictive as the system in Wuhan. But there, people were forced to do so much more. A lot of things also work for us because of a high willingness to cooperate as a society. In any case, it is right and necessary that we all avoid physical contact as far as possible. This is the only way to reduce the rate of infection. The key thing is to keep the infection rate as low as possible so that the health systems do not collapse. This must be our top priority! And this can only be done when there is hardly any physical contact, otherwise too many people will simply become infected and it will get out of hand. Or, to put it in more scientific terms: ...we need to get the rate of dispersion of the virus below 1. On average, each infected person may infect less than one other person - then the spread decreases and the virus is under control. If the distribution rate is above 1, the number of newly infected people increases steadily and sooner or later the health system risks collapse.

Is it sufficient to keep the virus under control? Wouldn't it be better to try to kill it completely?

That's a theoretical possibility. But then you would need a much stricter restrictions than the current measures. We would have to close the borders and put Luxembourg under a near total quarantine for six to eight weeks (for which we would then lack the nursing staff). That would be the time it would take for the new infections to terminate in the households as well.

But Luxembourg is right in the middle of Europe. The virus could easily be carried back into the country and everything would start all over again.

Exactly. Luxembourg cannot be considered in isolation. Nor do I think that option is realistic. I prefer what I call the "seeping fire scenario": In this scenario, we try to keep the number of new infections under control by using restrictive measures like avoiding physical contacts. We have to keep this number low so that not too many patients need intensive care and thus our health system does not collapse. This scenario is very similar to the principle "flatten the curve" (see infobox at the end of the article).