Q&A with HK microbiologist Yuen Kwok-yung who helped confirm coronavirus' human spread

Prof Yuen Kwok-yung shares how local officials dealt with the experts who tried to find out the truth at the very beginning of a public heath crisis. PHOTOS: THE HKU SCHOLARS HUB, AFP

HONG KONG (CAIXIN GLOBAL) - Sixty-three year old microbiologist Yuen Kwok-yung, a giant among Hong Kong's infectious disease experts, accompanied high-profile Sars researcher Zhong Nanshan and China Centres for Disease Control head George Gao on an exploratory mission to Wuhan on Jan 17 on behalf of the National Health Commission (NHC).

It was this "third expert group" that would sensationally confirm the new coronavirus was spreading between people.

Upon returning from Wuhan, the group recommended to the NHC that the city of 11 million be placed under lockdown.

Known for his outspoken personality and rich experience in public health, Prof Yuen tells Caixin what he saw and heard in Wuhan, and how local officials dealt with the experts who tried to find out the truth at the very beginning of a public health crisis.

A professor at Hong Kong University's medical faculty, Prof Yuen leads the university's research into infectious diseases, and he was a key figure in identifying and arresting the spread of the Sars pathogen that ravaged Hong Kong in 2003.

He is also on a four-person team advising the Hong Kong government on how to tackle Covid-19. He told Caixin how learning the lessons of Sars, and by acting early and decisively, the special administrative region has been able to keep its caseload to around 100.

He also reveals that eight of the nine Hong Kong residents who tested positive after disembarking the Diamond Princess cruise ship did not have symptoms of the disease, and says he helped spark Hong Kong's early emergency response after hearing from Chinese mainland researchers in late December their suspicions about the outbreak of a Sars-like virus.

He believes Hong Kong's health authorities were brave to declare an emergency as early as Jan 4, with the only flaw in their response being deferring the decision to close borders with the mainland.

He also wonders whether the Covid-19 outbreak was spread between different locations by wild animals, as well as by human transmission.

Here's our interview with Prof Yuen:


Tell us what you saw in Wuhan.

Let me tell you what I think is the truth. All the places we visited in Wuhan looked like they were putting on a show. Whatever we asked them, they answered as if they had prepared hard with well-thought-out replies. However, Zhong Nanshan was extremely sharp - he kept asking follow-up questions, like: "Is there anything else?" "Are there any more cases?" "Is it really like you're saying, just that many cases?"

They kept saying they were still testing, as the Hubei Provincial Centre for Disease Control and Prevention only received testing kits from Beijing on Jan 16.

Eventually, under pressure, they relented and told us it seemed that there was one patient in the neurosurgery department who had infected 14 medical workers. But they also said those medical staff had not had their diagnoses confirmed.

Microbiologist Yuen Kwok-yung in his office at Hong Kong's Queen Mary Hospital. PHOTO: CAIXIN GLOBAL

Who were "they"? When your group inspected Wuhan's hospitals, who was there?

People from the Wuhan Municipal Health Commission, the Wuhan Centre for Disease Control and Prevention, the Hubei health commission, and local hospitals in Wuhan.

Do you feel like they were hiding things from you?

While we were eating a meal, I remember seeing a deputy mayor (of Wuhan) sitting at the same table as Zhong Nanshan, looking very solemn. They probably knew something big was going on, because we were the third batch of experts who were sent. I believe that if they were hiding things previously, there was not much they could hide by that point, even though they kept emphasising the testing kits had only just been delivered to Wuhan, and no diagnosis could be confirmed without them.

After you flew to Beijing from Wuhan, what did you report to the authorities?

We met a deputy-level national leader and officials from the National Health Commission. They were all quite frank. Our expert group reported that the situation was severe, and there must have been cases of human transmission, and that preventive measures needed to be taken immediately.

I made two suggestions at the time. One was that the window left for us to prevent and control the spread was very small. If strict measures were not taken in the following days, the situation would further deteriorate. Another was about management and control of the wildlife trade and eating wild animals.

Biosecurity regulation has not kept pace with the development of China's food and drug industry. The desire to eat wildlife has caused large-scale infectious disease outbreaks over and over, while the rapid growth of the global population has accelerated the emergence and spread of infectious disease.

In 2007, I published a retrospective paper on Sars. The article mentioned that bats carry a large number of coronaviruses, and the Chinese cultural obsession with eating wild animals was time bomb for the next infectious disease outbreak.

(Editor's note: On Feb 24, the 16th meeting of the Standing Committee of the 13th National People's Congress stepped up enforcement of a ban on the unregulated wildlife trade, and a ban on eating wild animals, in order to protect the public health. The decision was put into effect on the date of announcement.)

So you were the ones who suggested Wuhan be locked down.

It was one member of the expert group who suggested Wuhan should be locked down. He is a professional, top-tier scientist in the field of epidemiology.

Did you visit the South China Seafood Market (linked to the early spread of the disease)?

The market was already closed by then, and I sat in the car with a bunch of people including Zhong Nanshan, Li Lanjuan, Zeng Guang, (China CDC head) George Gao, and so on. We drove around the market a few times, but one of the people accompanying us said we would not be able to see anything even if we got out of the vehicle.

I asked them what the market was like previously. George Gao said it was very dirty, surrounded by trash and rats. A really bad environment.

I was shocked that the market was right next to a very busy commercial centre. Although they were separated by a street, it was like a line between heaven and hell. Therefore, in addition to controlling the consumption and trade of wildlife, I also proposed when I was in Beijing that the environment and hygiene of food markets be better managed. In fact, every time I visit the mainland, I go take a look at local food markets, but the markets even in many big cities are still dank and smelly. They are very likely to become the origin of infectious diseases in the future, and therefore need to be cleaned up.

In fact, many of the wild animals sold in the South China Seafood Market before it was closed may have already entered different places around the country. Everyone thinks that the new coronavirus was spread to other provinces through human transmission. But who knows if it was carried around by wild animals before it was transmitted to local people? These questions cannot be answered at the moment.

The third group of experts confirmed the new coronavirus was spreading between humans, which became a turning point in the fight against the disease. What was the evidence underlying that judgment?

Scientists will not draw conclusions based on just one piece of evidence. At that time, there was a case in the Shenzhen Hospital affiliated with HKU where six members in a family of seven were infected with Covid-19, and one of them had never visited Wuhan. We admitted the patients to hospital on Jan 10, and basically confirmed the cases on Jan 12 using our rapid testing kits. After that, we went ahead to inform the disease and control centres of all levels in Shenzhen, Guangdong and Beijing.

That case of a family cluster, plus the case in Wuhan of one patient infecting 14 medical staff - together they were evidence of human transmission within hospitals, within families, and between cities. That was sufficient to say that the new virus was capable of spreading from person to person.

(Editor's note: By Jan 10, Yuen Kwok-yung's team had invented a rapid testing kit to test zoonotic coronaviruses within about six to eight hours. However, as Caixin previously reported, on Jan 3 the National Health Commission ordered institutions not to publish any information related to the unknown disease without authorisation. The first case in Shenzhen was not evaluated and confirmed by China's top health body until Jan 19.)

Zhong Nanshan once publicly said that the status of the China Centre for Disease Control and Prevention (China CDC) was too low, as the centre had only the right to make policy suggestions, and no administrative powers. Do you think Hong Kong has any experience to share for the mainland in the field of public health?

I think doctors in the Chinese mainland need to have professional qualifications that are reviewed by their international peers. This would mean that their proficiency was recognised in the international community, instead of just by a small circle of insiders.

An internationally recognised qualification would inspire trust from citizens and administrative institutions. If public health specialists made recommendations about the prevention and control of an epidemic, but the government ignored them and caused a major outbreak, the administrative organs would be responsible. If the doctors were the ones who told a lie, there would be a medical board or an academy to stand up and question them, possibly even revoke their licenses to practice.


As early as Jan 4, the Hong Kong government declared the epidemic an emergency, even though the cause of the pneumonia was not clear at that time, and there were no confirmed cases in Hong Kong. Why did the Hong Kong government respond like that so early?

We scientific researchers have our own circles where we exchange information. On Dec 31, 2019, I heard from some mainland researchers that a new virus had emerged, and it was suspected to be a Sars-like virus. It sounded like trouble.

I notified the Hong Kong SAR government as soon as I got the word. On that day, the Wuhan Municipal Health Commission announced a total of 27 patients were infected with pneumonia of unknown cause. By the evening, the Hong Kong government had already convened a small group of experts, after which the Department of Health asked the hospital authorities, customs and family doctors to step up health surveillance with a raft of measures.

We did not know how serious the virus was at that time, nor did we know it was a new type of coronavirus, but because the virus appeared in the winter season and we were told it was related to Sars, we decided to be very cautious, and the Hong Kong government took our opinions seriously. As scientists we should never neglect "soft intelligence", because this kind of information can sometimes be more timely than official warnings, like animals who can sense the coming of earthquakes and reacted ahead of time.

The Hong Kong government stipulated that patients with fever or pneumonia symptoms should be considered suspected cases if they had visited Wuhan within the previous 14 days. As a result, there were more than 100 suspected cases in Hong Kong before the first confirmed case. Why did Hong Kong adopt such a broad inclusion criteria for suspected cases?

Because this is a novel infectious disease, and no one knew enough about the transmissibility of the virus or way of spreading. We had to set the standards broad enough to ensure there were no fish slipping through the net to cause larger-scale spread in the community. In the early stages, there were many suspected cases in Hong Kong, but none of them were confirmed cases. Many people criticised the Hong Kong authorities, saying they were too jumpy and were creating panic. The head of the Food and Health Bureau, (Sophia) Chan, took a lot of flak for setting the response level to "emergency" at that time.

Hong Kong has a population of 7.4 million, and hundreds of thousands of them travel between the city and the mainland every day. An outbreak on the mainland is very dangerous for Hong Kong. Thanks to the strict prevention and control from the early stages, there are just over 100 confirmed cases in Hong Kong, even less than Singapore.

But there were still quite a number of locally transmitted cases in Hong Kong. Does that mean there were still loopholes in the containment?

The only issue was the timing of controlling flows coming in from the mainland. The Hong Kong government was indeed a bit slow in doing that.

In the beginning they limited the inflow from Wuhan and Hubei, but did not consider restricting inflow from the whole mainland. The first 10 confirmed patients in Hong Kong were all imported cases from the Chinese mainland, but after that there were only local cases. It was clear that the virus spread in the community because some infected people brought it across the border, hence if they did restrict the inflow from the mainland earlier, there would be fewer local transmissions. But nevertheless, the epidemic is currently under control in Hong Kong.

People wearing facemasks eat at a street stall during the evening rush hour in Hong Kong, on March 4, 2020. PHOTO: AFP

Unlike Sars, for which we could find very clear transmission chain, there have been many untraced cases of community transmission of this time. Why is the transmission chain so unclear?

Because many Covid-19 patients only have mild symptoms, whereas Sars could be easily identified once it infected someone. For example, among the 225 Hong Kong residents recently picked up by the Hong Kong government from the Diamond Princess cruise ship, nine were confirmed by diagnosis, but only one of them had clear symptoms before they were tested, and the other eight did not present with symptoms before their cases were confirmed.

Based on that proportion, if 100 symptomatic patients were found in Hong Kong, there could be 800 infected without showing symptoms, and they may not get a test because of that, hence would never have been confirmed. In fact, many patients with mild symptoms have healed on their own, but they may have transmitted the virus to others already, making it very difficult to track the transmission chain this time around.

Given this novel coronavirus is so "cunning", with probably many infected but asymptomatic people moving around in communities, how should ordinary citizens protect themselves?

We can only rely on telling everyone to wear a mask, wash their hands frequently, use alcoholic sanitiser. I had called for everyone to wear a mask when I was in Beijing, but many people disagreed, saying that the World Health Organisation (WHO) said healthy people don't need to wear masks unless they go to crowded places. Nevertheless, if people wear masks only when they feel sick, then the eight infected people on the Diamond Princess would have transmitted it to others because they were not feeling uncomfortable. Wear a mask to protect not only yourself but also others, because if you are infected but asymptomatic, you could still stop the spread by wearing a mask.

In our experiments previously, we found 100 million virus strands in just one milliliter of a patient's saliva. Therefore, scenarios with the potential for exchanging saliva are generally quite dangerous. The temporary success of virus control in Hong Kong this time is not only due to population controls, but also contributed by the early advocacy for mask-wearing, hand-washing, and social distancing. Otherwise, with such a dense population in Hong Kong, the epidemic would very likely have spread the same way as in Italy or Daegu in South Korea.

Schools in some areas of the Chinese mainland are preparing to reopen, but primary and secondary schools in Hong Kong are set to wait until after April 20. Why so late?

Because in schools, especially kindergartens and primary schools, children tend to grab each other when they play together, which would make it easy for the virus to spread. Their parents might not find out easily, since kids tend to have very mild symptoms after infection, probably only a minor cough and not even a runny nose. These kids may then pass the virus on to people who take care of them, such as their domestic helpers, parents and grandparents. That would cause the epidemic to break out in the community.

There have now been new cases imported from other countries to China, and we don't think the epidemic will end soon. Therefore, sending students back to school is a difficult decision.

Starting from March 2, 180,000 civil servants in Hong Kong have been returning to their offices. How should the city balance virus control and maintaining normalcy?

When the epidemic first started to surge with the number of new cases increasing exponentially, the most stringent measures had to be taken to cut off viral transmission as soon as possible. But after its growth slowed, with only one or two new cases a day, those strict controls can be gradually loosened.

So that's what Hong Kong is doing now, relaxing things one step at a time. First we put government workers back in the offices, after that, we will wait for 14 days to see if there will be an exponential increase during the incubation period. If there's no new outbreak after 14 days, universities could reopen, gradually followed by secondary schools, primary schools, and then kindergartens, slowly relaxing until society returns to normal.


As of now, there are confirmed cases on every continent except for Antarctica. Respiratory disease expert Wang Chen previously said the new coronavirus may never be completely eliminated. What do you think?

It's very clear that the epidemic is global. Sars in 2003 lasted for six months, with about 8,000 people infected and over 700 deaths. It has only been more than two months since the Covid-19 outbreak, but more than 100,000 diagnoses have been confirmed around the world, and more than 3,000 people have died of it. The novel virus has developed into a global epidemic in such a short time, which indicates that this epidemic is far more severe than Sars.

If Covid-19 adapts more and more to the human body, it will become increasingly difficult to keep track of. It is possible that the epidemic will not completely go away even when summer comes. But when the temperature gets higher, the condition of Covid-19 patients will become slightly milder, with more implicit transmission by asymptomatic virus carriers. I believe the temperature will have certain impact on the toxicity of the virus because, for example, when we do animal experiments on influenza virus, its toxicity in animals placed in 15 degrees Celsius (59 degree Fahrenheit) will be 10 times higher than in those in 25 degrees Celsius.

However, note that the epidemic has already spread to the southern hemisphere which is about to enter winter, and that could allow the virus to survive and thrive. The virus could wait for the northern hemisphere to enter winter later in the year, and come back from the southern hemisphere again. If that happens, the transmission of Covid-19 will continue.

Women with face masks are seen in Galleria Vittorio Emanuele II, after the Italian government imposed a virtual lockdown on the north of the country, in Milan, Italy, on March 8, 2020. PHOTO: REUTERS

Compared with Japan, South Korea and Italy, the situation in Indonesia, Philippines, India and some other countries seems to be well under control. Why do you think there is such a difference?

I believe it is probably on one hand related to temperature. Respiratory viruses such as influenza are usually less active in the hot summer. The other countries hit most by the epidemic, such as northern Italy, South Korea and Japan, have all been experiencing relatively low temperatures. Singapore's epidemic prevention measures are far less stringent than Hong Kong's, because it's hotter in Singapore, and the transmissibility of the virus is much lower when it gets to areas where the temperature is over 30 degrees Celsius.

However, on the other hand, we don't know for sure what the situation is like in many places. It is also possible that the low number of confirmed cases is related to less testing, because in many countries it's quite expensive to do the test, and some people can't even afford to see a doctor.

Take India as an example. Only three confirmed cases were reported in India before March 1, but there have been quite a number of cases in Hong Kong of our local residents who came back from India and got infected, therefore we do not really know whether the epidemic has broken out in the country.

People wearing face masks wait inside the terminal at Hua Lampong railway station in Bangkok, on March 9, 2020. PHOTO: AFP

Many countries such as Thailand, Japan, Australia and other places have proposed that residents or visitors who return from virus-hit areas should be quarantined at home or in designated places for 14 days. How did Hong Kong come up with such a measure in the first place?

Now it seems that many countries are learning that "trick" from Hong Kong. At that time, many people proposed shutting borders, but Hong Kong's economy is export-oriented, and if entries and exits were all banned, there is no way society could function. Therefore, my advice to the Chief Executive (Carrie Lam) at that time was to minimise the exchange of people to and from affected areas. The 14-day quarantine measure did not ban entries, but it managed to reduce many unnecessary exchanges. After the measure was taken, cross-border traffic went down by more than 90 per cent in a short time. And the measure also has some exemptions - for example, truck drivers who transport daily necessities. If every truck driver needs to be quarantined for 14 days each time they cross the border, most deliveries will end up suspended.

Despite multiple different virus outbreaks in recent years, there has never been a measure taken that was strict or long-lasting as the Wuhan lockdown. Was it necessary?

This lockdown method is quite a primitive containment measure for infectious disease. It was used when the bubonic plague broke out hundreds of years ago, and has not been used in centuries. When the epidemic in Wuhan entered a stage of exponential increase, the most stringent control measures had to be taken. This was a last resort, but the new coronavirus is too infectious, and transmits too quickly, and there are no drugs or vaccines available yet. We were not even clear exactly how to prevent it.

Actually, if the lockdown of Wuhan took place a bit earlier, the ultimate outcome would have been very different, because every day of delay resulted in many more new cases. From Jan 1 to the lockdown on Jan 23, there were roughly 1.6 incubation periods. Infectious diseases spread among human beings exponentially, which has created a lot of fear.

Therefore, we were all very concerned whether there was any person-to-person transmission in the early days, because human transmission raises the stakes and means transmission chains should be cut off promptly. In the beginning, the Wuhan Municipal Health Commission only said that it was transmitted from animal to human - if that was the case it was only necessary to shut down the seafood market to cut off the source of transmission.

I suppose the officials in Wuhan thought the same at the beginning, because the H7N9 bird flu and H1N1 swine flu in the past were just like that - once the market was closed, it was all right. Nobody expected the disease could be transmitted from human to human, until it quickly broke out in communities and hospitals.

Your team is also doing research on vaccines. How's it going?

We are currently in the phase of mouse trials, and have passed the safety test. There were no side effects in the medicated mice, and they produced antibodies. Now we are testing whether the amount of antibodies can provide sufficient protection, and whether those immune cells will attack cells infected by the new virus. After that we are going to do some virus-attacking experiments. But I estimate that it will take at least one or one-and-a-half years for the vaccine to be ready for clinical use.

This story was originally published by Caixin Global.

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