Hong Kong Epidemiologist Warns Against Easing Lockdowns "You Need the Sledgehammer" To Bring Down Infections

In an interview, Hong Kong-based epidemiologist Gabriel Leung explains why he considers a rapid lifting of contact bans and social distancing measures to be irresponsible. The corona crisis, he believes, will be with us for a long time.
Interview Conducted By Marco Evers
Epidemiologist Leung: "The objective must be to make sure you are not overriding your health system."

Epidemiologist Leung: "The objective must be to make sure you are not overriding your health system."



Gabriel Leung, 47, is one of Asia’s leading epidemiologists. He serves as the dean of medicine at the University of Hong Kong and regularly advises the World Health Organization, the World Bank and the Hong Kong and Chinese governments on their response to the new coronavirus. He played a major role in the containment of the first SARS outbreak in 2003.

DER SPIEGEL: Professor Leung, a total lockdown brings down the coronavirus, but it also brings down the economy and people’s hearts and minds. How long can society endure this?

Leung: We have to be very clear: This will be a marathon, not a sprint. I think we are going to be in a three-way tug of war between health protection, economic preservation and social acceptance.

DER SPIEGEL: And how long will this tug of war last?

Leung: Until at least half of the world’s population has got immunity. And there are only two ways of getting immunity: One is through infection and recovery, the other by a vaccine. But we are at least 9 months and more likely a year and a half away from a widely available vaccine that is effective and safe.

DER SPIEGEL: Can we manage the pandemic more intelligently and in a way that prevents unnecessary collateral damage?

Leung: I think so. But the objective must be to make sure you are not overriding your health system. The surge capacity of the health system directly influences the death rate. If your surge capacity gets overwhelmed, you have a breakdown of your health and hospital system, and that’s when large numbers of people die unnecessarily. So, you must manage and mitigate and suppress the outbreak in such a way that the number of people who would require intensive care or a respirator are well within what your health-care system can afford.

DER SPIEGEL: Should we aim to eliminate the virus?

Leung: No, we are not talking any more about having zero cases. Containment has failed everywhere. What we need is suppression, or better: cycles of suppression and lift, probably many of them. Can we go a little less than total lockdown and allow the economy to come back a bit? The answer is yes. But there are prerequisites. No. 1: Your population is already at a low or acceptable baseline in terms of the daily number of new patients. Prerequisite No. 2: You would need to do a lot better on testing and tracing. That would allow you to quarantine the highest risk individuals and isolate the already infected. This is a bit of a seesaw: If you don’t do testing and tracing well, then you will have to do a lot more on physical distancing. If your testing and tracking is done well, you may be able to relax the physical distancing a little more.

DER SPIEGEL: You are advocating for nations to follow a structured approach to the crisis. What would it look like?

Leung: You have to figure out how many cases you can tolerate and then tune your intervention accordingly. This is first determined by the number of intensive care (ICU) beds you have and the number of doctors and nurses to take care of them. You in Germany currently have enough capacity to even look after other European patients, which is great.

DER SPIEGEL: Is the number of beds the most important factor?

Leung: No, there should be more criteria. What is society ready to accept in terms of the number of people infected and hospitalized and the number of people who need to be ventilated and may die? There has to be an implicit or implied social acceptance.

DER SPIEGEL: How do we decide that?

Leung: The population will tell you and will tell politicians how much they can tolerate. There are some places that, for whatever reason, have a very low tolerance for adverse outcomes. Other places have higher tolerance. It is contextually specific. I don’t think one size fits all.

DER SPIEGEL: Why should we tolerate calamity?

Leung: The baseline is: Every year, the flu kills a lot of people in Europe, thousands, even tens of thousands. But you don’t get a riot every year. So, it seems to be acceptable to people to deal with that level of morbidity and mortality. Nobody likes it, but it is tolerated. Nobody asks for zero flu deaths. But if you exceed the capacity of your ICUs, then you would be breaching a very red line. So, somewhere between what people tolerate by implication every year and having completely overwhelmed ICUs like in New York City, somewhere between these extremes lie your tolerance levels.

DER SPIEGEL: How do we bring down the epidemic to a manageable level?

Leung: If you have a sustained outbreak like in most of Europe, you need the sledgehammer to bring down the Rt to below 1. Rt is the virus’s actual transmission rate at a given moment. But you need to go much below 1 to bring the baseline level to a low enough level that you can accept.


Leung: Rt of 1 means status quo. For every person who gets infected and recovers or dies, you replace them with one new infection. If your base line is 1,000 infections a day, then you would keep having 1,000 cases a day ad infinitum. Here’s what you need to do: You need to reduce Rt to much below 1 for a long period, so you bring down the number of new cases to say 20 per day. Then you can have Rt of 1 and have 20 new cases everyday ad infinitum, which is what you can deal with. You have to find out at what level you want to maintain an Rt of approximately 1 or just under 1.

DER SPIEGEL: Germany has an Rt of close to 1 according to the Robert Koch Institute, the country’s center for disease control. Some politicians are already talking of relaxing the measures.

Leung: You need to be very careful in how you estimate the Rt -- it is not a trivial estimation. Assuming it is above 1, I think it would be very premature to talk about any kind of relaxation. What you need to do is bring Rt to way below 1, and then determine what number of daily new cases would be an acceptable level.

DER SPIEGEL: How can authorities gather data to get a realistic real-time perspective of how fast the virus spreads?

Leung: You guys have a lot of very good epidemiologists in Germany, I don’t doubt they can estimate the Rt. Usually the stumbling block in Rt is twofold: One is to get it in a very timely way. And second: To supplement it with social mixing and social mobility data from mobile phones, geolocation systems or whatever, at the aggregate level, so you don’t need to breach any privacy. Once you’ve solved the major technical issues, you need the authorities to use it to make decisions. That to me is the rate limiting step in most countries.

DER SPIEGEL: Will technology play a huge role in this crisis?

Leung: It could. You guys are leaders in technology. I don’t see an issue with the technical bit. It is changing the mind-set to rely on this more than you rely on the everyday reported case count.

DER SPIEGEL: The daily tally is unreliable?

Leung: You don’t know what you’re counting. There is a long time lag and you are never sure even how much of a lag. Also, you cannot try to supplement it and come up with a systematic, objective way of trying to see where the case counting is going. When the Rt is competently estimated, you could statistically reduce the time lag and supplement it with mobility data.

DER SPIEGEL: In a large country like Germany could you have different Rts in different cities and different approaches?

Leung: You definitely need to have a subnational estimate, but you will also have different Rts in your cities. Yes, you need much more nuance so that you can more precisely target the measures.

DER SPIEGEL: Could you have a situation in which one city has to lock down, but another can loosen restrictions?

Leung: If the epidemic dynamics tell you to do so, then yes. Frankfurt and Munich could very well have different policies because the epidemic in the affected locations demands more precise and targeted policies.

DER SPIEGEL: Is fairness an issue here?

Leung: No. It is about making sure that you have precise and targeted measures at different places and different points in the pandemic. The fairness is in the preservation of life. That is ultimately the true mark of equity.

DER SPIEGEL: Should young people be allowed to more exposure?

Leung: Trying to be too clever by half in terms of trying to expose people who are at lower risk in order that they could use herd immunity to protect other people at higher risk -- I think it is not going to work. Unless you have a very, very compliant population and you have a very targeted, almost military precision in how you think people are going to behave.

DER SPIEGEL: There are reports in Germany, especially among the younger population, that people are not socially distancing nearly enough. Should we be worried?

Leung: Of course, we should be -- especially when you are in the growth phase of an epidemic. It is absolutely mandatory that if you want to minimize the morbidity and mortality burden that the community-wide acceptance of physical distancing gets very high acceptance at all levels of the population, young and old.

DER SPIEGEL: So, let’s take a view on our future course of action. Is it suppress and lift, suppress and lift again?

Leung: Before a vaccine becomes available, I am afraid that is going to be the new normal.

DER SPIEGEL: Wuhan has ended its lockdown. Does that mean that the next lockdown is just around the corner?

Leung: No. You only need to do that when your epidemic is completely out of control. There are gradations of distancing measures, from as simple as school closures to all the way to locking down a city, basically not allowing anyone to leave the home. What we hope to see is that we would have much less drastic physical distancing measures because we would be able to pick up the first few new chains of transmission early enough so that we then catch them. That would allow us not to go into full lockdown. A low threshold switch between suppression and lift would allow us to impose less drastic measures.

DER SPIEGEL: How come Hongkong has kept up so well in this crisis?

Leung: I never like to tempt fate. I always remain very, very alert about our outbreak here. So far, we are maintaining control.

DER SPIEGEL: Have you been better prepared because of the historic experience of SARS in 2003?

Leung: Absolutely. That sociological imprinting is deeply, deeply seared in the Hong Kong psyche.

DER SPIEGEL: Did we lack it in the West?

Leung: I think everybody will be on a very high alert after COVID-19. When all is said and done, you’ll see an absolute revision of how we do infection control, public health, epidemic control. But that is quite a few more months away.

DER SPIEGEL: Will this end the cultural practice of handshaking?

Leung: I don’t think so. It will come back.

DER SPIEGEL: Is this a déjà vu for you yourself as an epidemiologist?

Leung: Well, we’ve had SARS in 2003, in 2009 we had the swine flu and in 2013 the H7N9-influenca on the mainland. Every epidemic is different. But for researchers: I think it is very important to be humbled by nature.

DER SPIEGEL: What do scientists need to prepare for to fight this pandemic?

Leung: You need to have resilience. And to carry with you as a scientist a sense of humanity. Making sure we do the best science and know that we do the best science to keep people safe. And: To be absolutely resilient to external pressures.



The article you are reading originally appeared in German in issue 17/2020 (April 18, 2020) of DER SPIEGEL.

DER SPIEGEL: What should scientists be vigilant about?

Leung: Pandemics is never just about science. It is as much about politics as it is about science. As scientists, we must tender honest, unbiased, robust advice to our political leaders. They will, of course, have more considerations than just medicine, health or science. I think it is that interplay and tension that some of my colleagues including myself find difficult and challenging at times.

DER SPIEGEL: Rich countries can probably fight this off one way or the other. What do we do about other countries?

Leung: That is what I mean by equity and fairness. Unless the richer countries of the world deliberately and consciously come together in a sense of global solidarity, you’ll see amongst the lower- and middle-income countries a gross massive inequity happening with COVID-19 by omission. That is: If we do nothing, we’ll see the number of lives lost track very closely with the availability of ICU beds and the availability of good health care. And that we must never allow to happen.

DER SPIEGEL: Is the world rallying?

Leung: I don’t know, ask politicians. We need global leaders who believe in and champion health and human rights. And you have a chancellor who is very noted for both.

DER SPIEGEL: The only real exit strategy appears to be a vaccine. Do we know whether one will be found?

Leung: There are well over 100 of these studies being done. So, we should be hopeful, but we are not sure yet.

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