I'm recording this video on April 1, 2020. There have been 73,217 reported cases of coronavirus in Germany; 802 have died. Daycares, schools, and stores have been closed; social contact reduced to a minimum. Many have lost their jobs or are out of work, others are running themselves ragged to keep our country going. These measures are to stay in place until just after Easter [=Apr. 12]; after that, officials say we'll just have to see. But frankly, how long can our society go on under these conditions? I'm afraid we'll need perseverance...and quite a bit at that. As long as there's no vaccine, the pandemic will only end when 60-70% of the population has been infected. Or more precisely, when 60-70% have been infected, recover, and become immune. Then we will have "herd immunity," which means enough people are immune for the outbreak to sputter out. In Germany, 60-70% of the population means between 48 and 56 million people. Let's do some quick math: We have 73,000 reported cases in Germany. If we assume the number of unreported cases is 10 times as high (in other words, that for every reported case, there are 9 undetected cases) then we'd have 730,000 cases. Only 730,000 of 48 to 56 million cases. This means that we probably have just a little more than 1% herd immunity. This means: the corona crisis has only just started. So how long do we have to keep this up? So far, officials have been saying things like: "It's still too early to say." "We'll have to see how effective our measures are." "Only time will tell." There are a few things we really must talk about in depth and look at numbers we probably don't want to. So, make yourselves a tea, get comfortable, because this is going to take a while. First of all, it is of course appropriate to wait for the data about the efficacy of our current measures. We'll know in 2 to 3 weeks time, and I'd rather not make any guesses. With the path ahead unclear, it's best for us to move one step at a time; but it'd be great to know about how long this odyssey is going to be. ...and that experts already know a good deal about. With all of the media coverage of the corona crisis, this is the precisely the point I think has been discussed too little. So to begin, here is an introduction to the fundamentals of handling an epidemic. The phases of controlling an epidemic Phase 1: Containment This means restricting the spread of the sickness. Ideally, this means exterminating it before it even takes off. Containment measures include isolating the infected, finding and isolating their contacts, testing, keeping close track of the virus and preventing its spread. But things can easily go wrong, like in Hainsberg where one infected couple celebrated Carnival with 300 people, which of course quickly escalated the spread of the virus. Eventually, tracking the infected and each of their contacts exceeds our administrative capabilites. Begin Phase 2: Mitigation In other words, damage control. When it's no longer possible to know who's infected, isolating only a select few no longer works. Now all of us have to become involved: physical distancing, home office, cancelling events, and so on. You've all been there. In this phase, we've already given up on our attempts to contain the virus, instead we're trying now to slow its spread. You've probably already heard why this is so important. Since basically everyone has been talking about "flatten the curve," the basic principle of mitigation is probably clear to everyone; however, this purely qualitative understanding can be misleading. So to recap: The slower the virus spreads, the fewer the people who have the sickness simultaneously and therefore simultaneously need medical treament. By doing so, we prevent our overwhelming our hospitals, the horrors of which we are currently watching unfold in Italy, Spain, and New York. When the ICU doesn't have enough beds for their patients, impossible decisions have to be made about who lives and dies. We cannot allow this to happen. The problem is that many seem to think, "The lockdown is rough, but we're doing our best, "and hopefully we'll be able to make the curve so flat that "we'll all be able to put this behind us by Easter, maybe a little bit later." This is unfortunately... ...quite far from the truth. We can understand why when we look at the numbers. Let's look at an important variable: the reproduction number. The basic reproduction number R0 specifies on average how many people an infected person will infect when no one is immune and no measures are in place. For the SARS-Coronavirus-2, R0 is estimated to be 2 to 3. That means each infected person infects 2-3 other people. When the reproduction number falls under 1, which means each infected person infects less than 1 additional person, then the outbreak will come to a halt. All of the measures put in place the last few weeks from washing hands to tracking contacts to the lockdown were meant to reduce the reproduction number, that is, the effective reproduction number. Visually speaking, the smaller the reproduction number, the flatter the curve. But how flat is flat is flat enough? The German Society for Epidemiology provided an answer to this question in their statement about the spread of the new coronavirus. Here, we find models for different scenarios. It must be noted that these models are not predictions. Every epidemic is unique, which is why researchers are working tirelessly to understand this particular virus better. However, models can illustrate various plausible scenarios, providing a framework for understanding what the future could look like. Using these scenarios, we can deduce how each measure would affect the spread of the virus. So: How would the effective reproduction number affect the course of the epidemic? Or rather: How low does the effective reproduction number have to become in order for the curve to become flat enough— that is, flat enough for our health care system to handle? For this, we first need to know how much the German health care system can handle. This is dependent on a number of factors: ventilators, protective equipment for the staff, and of course the staff itself. But let's just take a single limiting factor we can work with, namely the number of beds in the ICU needed to treat the severe corona cases. In Germany, there are approx. 30,000 intensive care beds. But not all of these are free. Despite all efforts to increase our capacities, some of these beds will be needed by non-corona patients. But let's assume anyway for our calculations that we had 30,000 free beds. How many people will need an ICU bed due to the coronavirus and how long will they need it for? The German Society for Epidemiology estimates that 2-6% of those infected by the coronavirus will need an ICU bed. The length of hospital stay is relatively long: 10 to 20 days, depending on the patient. Here are the models of 9 different scenarios. With 2, 4, or 6% of cases needing intensive care and 10-, 15-, or 20-day hospital stays. Let's look at the best-case scenario, in which only 2% of the cases need intensive care and each only for 10 days. In this scenario, if we had a reproduction number of 1.5, so the green curve, we'd greatly exceed our health care capacities for a very long time. Even with a reproduction number of 1.25, we would be closer to the 30,000 bed limit, but we'd exceed it during the peak anyway. And if it's not just 2% but 4%, then twice as many patients will be in need of intensive care. In most of these scenarios, the reproduction number has to go down to 1.1, or at least close to 1.1, in order to not overwhelm our health care system. And in the worst-case scenario, even with a reproduction number of 1.1, we have during the peak 10,000s of people every day who cannot get treatment. In summary: In order to not overwhelm our hospitals, we need measures that will push the effective reproduction number down to a value between 1.25 and 1.1. This is only possible with strict physical distancing. But let's look at the timeline: with these rigorous measures, the epidemic would be over in a year at the earliest, in most of the cases, much longer. The flattest curve, in dark blue, it's even cut off. That one lasts more like two years. Bottom line: To avoid our health care system from breaking down, we have to keep strict measures in place for 1 to 2 years. And that...won't...work. We are already beginning to see the havoc it's wreaking on our national economy. There are livelihoods, and thus also human lives, on the line; not to mention the impact it'd have on our society at large, on our psyches... we can't even fathom these things at the moment. I know that for these models assumptions and simplifications were made, and I also know that there are parameters about COVID-19 that we do not yet know but are not unsignificant, such as the precise role of weak or asymptomatic cases, but just think about the order of magnitude. If our understanding of the magnitude isn't completely off, then flattening the curve until herd immunity is not doable. This view is not entirely new. It was published the day of Chancellor Merkel's speech and updated a few days later. But when I look at the media coverage, the message still seems to be that flatten the curve is still the master plan. How can that be if it is so obviously not going to work? I also talked to Prof. Mikolajczyk, one of the co-authors of the joint statement, to make sure we haven't completely misunderstood the situation. Thank you for the very informative off-the-record conversation. So, as it stands, there is no other way to interpret the findings. The answer to the question, "How much do we have to reduce the reproduction number "for the curve to be flat enough?" is that the reproduction number must drop to below 1, because the flattening itself would take too long. We have to stop the curve. We need to do a hard reset. The number of cases must become so low for our health departments to be able to target and track individual cases. Then we'd be able to effectively isolate the sick, track whom they've contacted, and break chains of contact to contain the virus. This means, when the number of cases don't just increase more slowly, but begin to fall, then we'll eventually come back to a point where we can use the measures from Phase 1, Containment, again. And then—that's when we could return to something that resembles normalcy for many people because then the strict measures would apply only to the infected and those they've come into contact with. The only thing is: the way back to Phase 1 is only possible if the rigorous measures are held by everyone. Again, this means an infected person must infect less than 1 other person in order for this to work. Think of how easy it is to get 2 others infected, especially when you're not worried because your symptoms are mild. Or if one person infects 10 people at an event, then 9 other infected people "can't" infect anyone. So, are the current measures sufficient to push down the reproduction number that low? This is precisely the assessment we're waiting for. But we can say this much: It was without a doubt the best course of action for the lockdown to be put in place. If we really want to get back to Phase 1, then what we are doing now is by no means excessive or too severe. But we can say already that we are quite far from a sufficiently low number of cases. Let me show you why: There are a number of online epidemic simulators that you can play around with. Just to illustrate: (I like this one) you can adjust the parameters like contagiousness, hospitalization rate, and so forth, to set it up with the working values that the German Society for Epidemiology used and see how long it will take until we can revert to Phase 1. For this, I have to assume how low the number of cases has to drop, or at which case count containment would again be possible. The actual number is heavily dependent on our testing capacities, on how many resources and staff we can allocate to the respective administrations, how good the infrastructure is, etc. But let's just use as an indicator the day Jens Spahn [Germany's Secretary of Health] declared events with over 1000 participants should be cancelled, because keeping track of the cases apparently became a problem by that day at the latest. On that day, there were about 1000 cases in Germany. So let's assume that 1000 is a case count where the sickness could still be contained without everyone needing to practice strict physical distancing. Sp today, we have about 17,000 cases. Here we can adjust the model so that the day it reaches 17,000 cases, the reproduction number drops from 2.0 to 0.5. Reproduction number 0.5 is really giving it all we've got. Think of it as Wuhan-style lockdown. With these basic assumptions, it'd take 56 days until we'd have less than 1000 cases, so almost two months. This is not meant to be a prediction, but an example scenario to get a good feeling for how long this could take. Please don't get the wrong impression: if we are able with rigorous measures to get back to Phase 1, the epidemic is still not over. It only means we are merely returning to a state in which our health care system as well as our economy can function again— a state our society can at least bear until the epidemic is finally over. Quick sidenote: There are are a few unknown characteristics of the virus that could help end this more quickly. For example, seasonality: it could be that the virus *might* be less contagious in the summer. Or that part of the population *could be* innately immune to the disease. The Robert Koch Institute has generated models for this. You can find a them and other useful links in the video description. But it wouldn't change anything about our strategy. It would be wrong for us to loosen the measures based on a faint, unverified hopeful idea because at the end of the day, the faster we are back in Phase 1, the better. This all sounds like extremely hard work only to get back to where we were a month ago. But you must know: we're not just taking a step back, It will be better the second time around. The containment phase at the beginning of an epidemic is posed with this dilemma: The earlier you impose measures, the more effective it is; but since the beginning of an epidemic doesn't seem so bad, the threat is not recognized until it's too late. Many people here didn't take the coronavirus seriously first. Lawmakers are only one part of the puzzle; without cooperation from the population, it is virtually impossible to cancel Carnival in a democratic society. But when we again return to containment, we'll all know what to do. By now, all of us are experts at washing hands, coughing into your elbow, and physical distancing and even take measures of our own like sewing our own face masks. Our health care system and our research have made great progress. We are currently we are expanding our testing capacities. The administrations are boosting its manpower, and so on. Let me be clear, I believe that Germany reacted reasonably to the coronavirus. But if we were to repeat Phase 1, we would do all manner of things much better, simply by virtue of knowing some things we didn't before. I should emphasize that we are striving to loosen the measures and win back some hint of normalcy. But we *will* still have tp sacrifice a great many things for a long time to come. This includes avoiding groups of people like concerts, crowded stadiums, popular outing locations, conferences, etc. You can forget all of that for this year. It would be too risky in the containment phase. A single outbreak could eliminate all of our hard work. Ski parties this coming winter? I don't see it happening because I have one more timeline for you: When will the epidemic end? I gave a basic answer to this at the beginning: the epidemic will only end when we've achieved herd immunity ...but that's just in theory. In reality, we can essentially forget ever achieving herd immunity. There is no scenario in which we can reach 60-70% herd immunity without inconceivable damage to society as a whole. Either we would completely overwhelm the capacities of our health care system, resulting in an appalling number of deaths, Or we'd work to achieve herd immunity without without overwhelming the health care system, but this process would take so long that it would be neither socially nor economically feasible. So I can only conclude that this epidemic will only end when we have a vaccine. Or with medication that would replace most of the hospital treatment, but that is unfortunately unlikely. This means we have to tough it out until there's a vaccine. Its development takes time; some optimistic estimates project spring 2021. And in order for us to get through all this with relatively little damage, we *must* implement rigorous measures *now* so we can return to the containment phase, a state in which we can at least get by and live with relative normalcy. I know that many of you were probably discouraged by what you heard here. I see it this way: I'd rather have a realistic idea as to how this will all end, even if it's hard to hear, than having to live in uncertainty. Knowing our end goal, we can get there more quickly. We can already start implementing new measures: expanding home office infrastructure where possible and think now about how we're going to try to get through this period. It'll be a marathon of endurance, but even though I can't understand how humans can run 42 kilometers, somehow they do anyway. So keep fighting, my Friends of the Sun, and if you have any motivating thoughts or ideas how we can hold out longer, please leave them in the comments. I hope you're all healthy and keeping your spirits up through this surreal time. I'm doing well. My baby has arrived! It's a very, very cute Friend of the Sun and thankfully all of us are healthy. But my heart goes out to everyone who have been affected by COVID-19, either personally or their loved ones. To all of you who are giving it your all to keep our country going, be it in health care or our infrastructure, and also to all of you who aren't able to work or aren't getting paid: this is an unspeakably difficult time. I'm fortunate enough to be able to produce maiLab from home, even if our team needs a little more time than usual since both Lars and Melanie have toddlers at home. This is why Melanie wasn't able to make graphics for this episode. But—perhaps you noticed that she's made a new channel design that I think is really cool. We hope you like it, too. Physical distancing has taken a huge psychological toll on us all. If you're also struggling, I can recommend a video by my dear colleague Pia. Pia's started her very own FUNK channel: psychologeek. Check it out and send her my regards, aka. cookies from me. And finally, we'd like to give a belated—but all the bigger—THANK YOU for your amazing support. First of all, thank you for the very sweet comments on our last video. I was deeply moved. You all made it both very easy and very hard for me to go on maternity leave. And thank you to everyone who sent me messages during my break the last few months. I read them only sporadically, since I not only took a break from YouTube but also from social media and email. But I'm happy to be back, also on Instagram and Twitter. Share this video with anyone who could be interested and tell your friends that maiLab is back! We'll bring you a new video every other Thursday so we'll see you again in two weeks. And until then— and there's no time more appropriate to say it— stay safe.