Monday, 20 April 2020

Corona Virus Update: the German situation improved, but if we relax measures so much that the virus comes back it will not be just local outbreaks (part 32)

The state of the epidemic has improved in Germany and we now have about half number of people getting ill compared to the peak we had a month ago. This has resulted in calls to relax the social distancing measures. The German states have decided that mostly nothing will happen the next two weeks, but small shops will open again (and some other shops) and in some states some school classes may open again (although I am curious whether that will actually happen, German Twitter is not amused).

An estimate of the number of new cases by the date these people got ill. Similar graphs tend to show the new cases for the date they were known with the health departments, by looking at the date people became ill, which is often much earlier, you can see a faster response to changes in social distancing. In dark blue you see the cases where the date someone got ill is known. In grey were it was estimated because only the case is know, but not when someone became ill. In light blue is an estimate for how many cases will still come in.

So in the last episode of the Corona Virus Update science journalist Korinna Henning tried to get the opinion of Christian Drosten on these political measures. He does not like giving political advice, but he did venture that some politicians seem to wrongly think measures can be relaxed without the virus coming back. The two weeks that the lockdown continues should be used to prepared other measures that can replace the lockdown-type measures, such a track and trace CoronaApp and the public wearing everyday masks.

Another reason it may be possible to relax measures somewhat would be that the virus may spread less efficiently in summer. It is not expected to go away, but the number of people who are infected by one infected person may go down a bit.

When the virus comes back, either because we relaxed social distancing too much too early or because of the winter, it will look differently from this first wave. This first wave was characterized by local outbreaks. A second wave would be everywhere as the virus (and it various mutations) are spreading evenly geographically.

Korinna Henning asks Drosten to explain why it is easier for him to call COVID-19 a pandemic than for the World Health Organization. This question was inspired by Trump complaining that the WHO called the pandemic too late. Drosten notes that it has political consequences when the WHO calls the situation a pandemic, but that does not influence the situation in your country and what Trump could have done.

Really interesting was the part at the end on some possible (not guaranteed) positive surprises.

Prof. Dr. Christian Drosten, expert for emerging viruses and developer of the WHO SARS-CoV-2 virus test, which was used in 150 countries.

The situation and measures in Germany

Korinna Hennig:
What's your assessment, how long would [the reproductive rate] have to stay below one for it to have a really long-term effect and we're not going to say that at some point we have to close all the schools again.
Christian Drosten:
I believe there is talk of months [in a report by the Helmholtz Association]. I can well believe that this is the case. However, this is not the path that has been chosen in essence [by the German government], but rather - I believe - the idea has arisen that the intention is to keep it within the current range, perhaps by taking additional measures to reduce the pressure a little more.

That is an important point of view, and one that needs to be understood. It is not primarily a question of saying that we have now achieved a great deal, that the measures have already had a considerable impact. And now we are simply letting them go a tad, because we no longer want to. Then at some point we will have to take a look and then we will have to consider how to proceed, that is one view.

The other is that everything will work out fine. Sometimes you can hear that between the lines. I have the feeling, particularly among the general public, that many people, even in politics, are speculating that it will not come back at all, that it will not pick up any momentum. Unfortunately, that is not what the epidemiological modelers are saying, but it is generally assumed that, if nothing is offered as a counter-offer to this relaxation of measures, it will really get out of hand.

And the idea is, of course - and this is a very real idea in Germany - that people say that they are now relaxing these measures to a small extent, but to a really small extent. It is rather the case that corrections are being made in places where we think we can perhaps get away with it without the efficient reduction of transmission suffering in the first place. And now, in the time that has been gained by the decision, it is preparing to allow other measures to come into force. And this of course includes the great promise of automated case tracking.

The cell phone tracking ... doesn't have to do the job completely, but you can combine it. You could say that there is a human manual case tracking system, but it gets help from such electronic measures, while you introduce these electronic measures. After all, this is not something that is introduced overnight; there must be some transition. I believe that the few weeks of time that have now been gained once again can be used to introduce such measures, and that is where a great deal of faith comes from at the moment.

Of course, there are other things to hope for as additional effects, such as, for example, a recommendation on the wearing of masks by the public. That could have an additional effect. Of course there will also be a small additional effect on seasonality. We have already discussed this, and there are studies which say that, unfortunately, there is probably not a large effect on seasonality, but there is a small effect on seasonality.

That is where things are coming together, so that we hope that the speed of propagation will perhaps slow down again overall and that we will at least be able to enter an region over the summer and into the autumn, where we will unfortunately see the effect of winter coming again, a possible winter wave, but where we will then have the first pharmaceutical interventions. Perhaps a first drug, with which certain risk patients could be treated in an early stage. Maybe first use studies, so efficacy studies of first vaccines. This is the overall concept, which one hopes will work.
Currently one infected person infects 0.7 or 0.8 other persons (RO, the reproduction number). That is behind the decline in the number of new cases. Theoretically you could thus allow for 25% more contacts while still being in a stable situation. I would be surprised if the small relaxations decided for the next two weeks would do that. I do worry that these relaxations make people take to problem less seriously and that can quickly lead to 25% more contacts.

I would personally prefer this decline to continue until we get to a level where containment by manual tracking infected people and their contacts becomes an effective way to fight the epidemic; Mailab explains it well in German.

If we get the tracking of infected people with a CoronaApp working, it would matter much less at which level of contagion we start, but I do not expect that the CoronaApp will be able to do all the work, it will likely need to be complemented by manual tracking. With the current plans, according to rumours in the media, placing less emphasis on privacy of the users, I worry that too few will participate to make any kind of dent. An app were we can only hope and need to trust that the government keeps its side of the bargain and does not abuse the data would also be less useful in large parts of the world where you can definitely not trust the government.

That some states are already starting with opening up some classes is in principle a good thing. But it goes too fast, the schools are not prepared yet and I see quite some backlash coming. If done well, by opening a few school classes we could have learned how to do this before we do more and we could study how much this contributes to a higher reproduction number R0. If we are lucky maybe hardly; see the last section on possible positive surprises.


The flu normally goes away in summer, this is not expected for SARS-2, but the reproduction number could be 0.5 lower, that is that one infected person would infect half a person less. Without measures it is expected to be between 2 and 3 and we have to keep this reproduction number below 1 to avoid that the situation gets out of hand again. The summer may thus help a bit, which could mean less stringent restrictions.

It is not well understood what exactly makes the summer harder for the flu and even less for SARS-2. One aspect is likely that people are outside more and ventilate buildings more, which dilutes and dries the virus. Also when it comes to schools, it may be an option to do the classes outside, where the distancing rules could be less strict than indoors.

Museum could create large sculpture gardens outside for the summer. As the conference centres are empty and unused they could be used as social distancing museums. The empty hotels could be used to quarantine people who might otherwise infect other people in their households. We have to support the hotels anyway to survive until the pandemic is over.

I have often dreamed of conferences while walking outside in nature. You could transmit the voice of the speaker with a headset. The power points slides with Comic Sans would be missing. This may be the year to start this as alternative to video conferences. (Although there would still be transport.)

World Health Organization and Trump

Korinna Hennig:
Could you briefly explain again what the difference is when you say here in the podcast for example: Yes, we have a pandemic in an early phase. And the WHO is still hesitating for a very long time. What is the crucial difference when the WHO makes such an assessment?
Christian Drosten:
So I am only an individual and can give my opinion, which you can follow or not. You can take me for someone who knows what he's doing. Or you can say: He's just a fool and he says things here.

Of course, this has different consequence with the WHO. In the case of a UN organisation, this has certain consequences, not only when it comes to saying that this is a pandemic, but also, and especially, when it comes to saying that this is PHEIC, i.e. Public Health Emergency of International Concern. That is a term used in the context of international health regulations. This then also has consequences for intergovernmental organisations. This scope has certainly also led to delays in all these decisions by the WHO.

Of course there are advisory bodies. After all, the WHO is not a person, but an opinion-forming and opinion-collecting organisation. Experts are called together, committees that have to vote at some point and where there is sometimes disagreement. And then they say that we will meet again next week and until then we will observe the situation again. This then leads to decisions that are perceived as a delay by some countries. This is an ex post evaluation of the WHO's behaviour.

At the moment this is again all about politics. And it is about a decision by Donald Trump, who has now said that he is suspending the WHO payments, the contributions, because the WHO did not say certain things early on.

It was, of course, known relatively early on from individual case reports that cases had already been introduced in the USA. And now to say that it is a pandemic that is taking place in all other countries ... So the statement that this is a pandemic is to acknowledge the situation, that this is far is widespread. This has nothing to do with the assessment for your own country. Since you know, it is in your own country, you have to ask yourself: Will do I act or not?
Korinna Hennig:
And there are of course financial liabilities between countries that are linked to the WHO.

Local outbreaks in wave 1, everywhere in wave 2

If there is a second wave, it will not look like this first wave.
Christian Drosten:
What happened in the case of the Spanish flu was this: We also had a first wave there in some major US cities - that is very, very well documented - that caught our attention. However, it did not occur in all places, but was distributed extremely unevenly locally. It was conspicuous here and there, and elsewhere people did not even notice that this disease existed at all.

Even there, even at that time, people were already working with curfews and similar things. This was also happening in spring, by the way. Then it went into the summer and apparently there was a strong seasonal effect. And you didn't even notice the disease anymore. And under the cover of this seasonal effect - we can perhaps now envisage this as, under the cover of the social distancing measures that are currently in force - this illness has, however, unnoticed, spread much more evenly geographically.

And then, when the Spanish flu hit a winter wave, the situation was suddenly quite different. Then chains of infection started at the same time in all places because the virus had spread unnoticed everywhere and no one had paid any attention to it. This is of course an effect that will also occur in Germany, because we do not have a complete ban on leaving and travelling here, and of course we do not have zero transmission either, but we have an R, i.e. a reproduction number that is around or sometimes perhaps even slightly below one. But that does not mean that no more is being transmitted.
So you can look at our homepage, for example, at the Institute of Virology at the Charité - we have now published a whole set of [virus] sequences from Germany. You can see that the viruses in Germany are already very much intermixed, that the local clustering is slowly disintegrating and that all viruses can be found in all places. So let me put it very simply.It is slowly but surely becoming very intermixed. ...

We'll be in a different situation when winter sets in. ... Suddenly you'd be surprised that the virus starts everywhere at once. Of course it is a completely different impact that such a wave of infection would have.
What I find interesting to see it that there is nearly no difference in virus activity between cities and rural regions in Germany anymore. If anything, just looking at the map below, I have the impression that rural regions have more virus activity. On the other hand, in the beginning, I feel there was more activity in the cities.

Yesterday's map of the RKI, the German CDC, of the number of new cases over the last week per 100,000 inhabitants. The larger cities are denoted by a small red dot, the location of the smaller cities can sometimes be seen as a smaller region in a different colour. The darkest region is an outbreak, which was likely due to a strong beer feast.

Positive surprises

Christian Drosten:
It is also quite possible that there will be positive surprises. For example, we still know nothing about children. It is even the case that in studies that are very systematically designed, this effect is often still left out. We know from other coronavirus diseases, especially MERS, that not only are children hardly affected, but they are hardly ever infected. Now the question is, of course, whether this is also the case with this disease, that not only they do not get any symptoms and are therefore not so conspicuous in the statistics, but that they are somehow resistant in a certain way and that they do not even have to be counted in the population to be infected. So what is 70% of the population? Is it possible to consider the 20 percent of children as finished, because they do not get infected at all? In reality, only 50 percent of the population need to be infected? This is a big gap, which can also be interpreted as a great hope.

And there is something else - we are anticipating that, epidemiological modellers are doing that, and they are taking that into account: That there may be an unnoticed background immunity from the common cold corona viruses, because they are already related in some way to the SARS-2 virus. It could happen, however, that certain people, because they have had a cold from such a corona virus in the last year or two, are protected in a previously unnoticed way.

All I want to say is that we are currently observing more and more - and a major study has just come out of China in the preprint realm - that in well-observed household situations, the secondary attack rate, that is to say the rate of infected persons who become infected when there is an index case in the household, an infected person, is quite low. It is in the range of 12, 13, 14 percent. Depending on the correction, you can also say that it is perhaps 15, 16, 17 percent. But it does not lie at 50 or 60 percent or higher, where you would then say that these are probably just random effects. The one who didn't get infected wasn't at home during the infectious period or something.

How is it possible that so many people who were supposed to be in the household are not infected? Is there some sort of background immunity involved?

And there are these residual uncertainties. But at this stage, even if you include all these residual uncertainties in these models, you still get the picture that the medical system and the intensive care unit capacity would be overloaded. That is why it is certainly right at the moment to have taken these measures. We must now carry out intensive research work as quickly as possible, as we clarify issues such as: What is really wrong with the children? Do they not get seriously ill, but are they in fact infected and are giving off the virus and carrying it into the family? Or are they resistant in some way? The other question that we absolutely must also answer is: why do relatively few, perhaps even cautiously put, unexpectedly few get infected in the household? This is a realisation that is now maturing so slowly.

As I said, a new preprint has just appeared from China, and a few other studies suggest that this is the case. The Munich case tracking study, for example, has already hinted at this a bit. You have to take a closer look at that. Is there perhaps a hitherto unnoticed backgroundimmunity, even if only partial immunity?

That wouldn't mean that we were wrong at this point in time, and what we have done now was wrong. At the moment, even if you factor in these effects, you get the impression that it's right to stop this, that we're not getting into such a rampage that we can no longer control. But for the estimation of how long the whole thing will last, new information could arise from this. It could then be - and I would like to say this now, perhaps as a message of hope - that in a few weeks or months, new information will come out of science that says that the infection activity will probably stop earlier than we thought because of this special effect.

But I don't want to say that I can announce something now. These are not hints from me, or data that have been available for a long time, but that I wouldn't want to say in public or anything. Rather, they are simply fundamental considerations that we simply know too little about this disease at the moment. And that the knowledge, which is actually growing from week to week, will also influence the current projections.

Other podcasts

Part 31: Corona Virus Update: Don't take stories about reinfected cured patients too seriously.

Part 28: Corona Virus Update: exit strategy, masks, aerosols, loss of smell and taste.

Part 27: Corona Virus Update: tracking infections by App and do go outside

Part 23: Corona Virus Update: need for speed in funding and publication, virus arrival, from pandemic to endemic

Part 22: Corona Virus Update: scientific studies on cures for COVID-19.

Part 21: Corona Virus Update: tests, tests, tests and how they work.

Part 20: Corona Virus Update: Case-tracking teams, slowdown in Germany, infectiousness.

Part 19: Corona Virus Update with Christian Drosten: going outside, face masks, children and media troubles.

Part 18: Leading German virologist Prof. Dr. Christian Drosten goes viral, topics: Air pollution, data quality, sequencing, immunity, seasonality & curfews.

Related reading

This Corona Virus Update podcast and its German transcript. Part 32.

All podcasts and German transcripts of the Corona Virus Update.

1 comment:

  1. Germany is down from 5000 cases per day to 1000 cases per day. Figure 4:

    With a testing capacity of 800k tests per week we are getting in the region where testing and quarantining people can replace of lot of the lockdown.

    The mandatory lockdown was never very strict in Germany, but the population is well educated and well informed (thanks Prof. Drosten) and did a lot (and did this early).

    It is relatively easy to stay at home as we have paid sick leave. We have universal health care, so that people who loose their job do not lose their insurance.

    Also just 0.6% people lost their jobs since February, most workers are on “short work”, they work less hours and the salary difference is compensated partially by the unemployment insurance and their employer. This way it is much easier to get back to work, no time consuming hiring and training.


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