Global epidemiologist sounds cautious note on COVID-19

By Wendy Haaf

Gabriel Leung

When Dr. Gabriel Leung speaks, the world listens.

The dean of medicine at Hong Kong University (HKU), Leung, MD’96, made international headlines in January when he announced that, based on modelling, the number of COVID-19 cases in Wuhan were likely dramatically higher than China’s official outbreak total.

But his introduction to novel viral pathogens started back in 2003 with a call from a fellow Western alumnus.

Leung had been conducting a series of cohort studies in non-communicable diseases in HKU’s department of community medicine when he received a call from Dr. Margaret Chan, BA’73, MD’77, DSc’99, Hong Kong’s then director of health and current head of the World Health Organization.

“(She) asked us to drop everything,” Leung recalled in a 2018 Lancet profile. Their shared emergency task: fighting what would become known as SARS.

It was an experience Leung has called his ‘baptism by fire’. He would go on to lead Hong Kong’s efforts against Influenza A (H1N1) in 2009 during a four-year stint in civil service, and conduct research that defined the epidemiology of two novel viral epidemics in addition to COVID-19: SARS-COV in 2003, and Influenza A (H7N9) in 2009.

Leung’s career trajectory as one of the world’s leading epidemiology and global health experts has been anything but predictable. He had been a piano prodigy in his childhood, then majored in chemistry and minored in music through Western’s then-new scholar’s elective program.

Initially, following his mother’s brain tumour diagnosis, he wanted to become a neurosurgeon. But, realizing he was more of a ‘people-person’, he switched to family medicine.

After completing a residency at the University of Toronto and a master’s in public health at Harvard, Leung joined HKU’s department of community medicine. He later received a research doctorate from HKU, and became a full professor in his early 30s, before his appointment as HKU’s youngest-ever dean of medicine in 2013.

Now, as dean, Leung has helped provide medical students at HKU with a well-rounded experience – similar to the one he received at Western – by incorporating humanities courses and events such as concerts and movie screenings into the curriculum.

His love for music meanwhile, has never waned. Today, he is also a chamber music pianist and has performed as a guest conductor with the HKU Union Philharmonic Orchestra.

Given his early, accurate, predications on the initial trajectory of COVID-19, where does Leung see the pandemic headed now? “The only way an epidemic with a completely novel pathogen – where there is no pre-existing immunity in the population – is going to die down, whether it’s going to become extinct, or, more likely, to become endemic, is for a sufficient proportion of the world’s population to develop immunity to it,” he explained.

“And there are only two ways for that to happen: through natural infection and then recovery, or through vaccination,” he said. “Given that a vaccine is not going to be widely available — I’m talking about having sufficient doses for sufficient numbers of people so it actually has a population effect — until probably nine to 12 months from now, we’re going to see continuing waves of flare-ups.”

Leung said the likelihood of future COVID-19 outbreaks is further increased as local outbreaks multiply in countries where restrictions are easing. “When you talk about travel bubbles, when you talk about reopening, you are increasing population mixing, both in countries and between countries.

“Secondly, the additional seasonal forcing in humidity and temperature that comes with autumn and winter in the northern hemisphere makes respiratory bugs much easier to spread, just like the flu,” he added. “A combination of those two things almost guarantees a second wave.”

That said, he is hopeful the second wave may not be catastrophic, or even substantial.

“It really depends on what we’ve learned from the first wave.”

Keeping it under control will require concerted efforts to protect those who are most vulnerable, which includes not only older individuals living in institutions, but those belonging to disadvantaged groups and those who live or work in crowded facilities.

“Appropriate physical distancing, that’s flexible and responsive to changes in transmissibility, is critical. Testing infrastructure needs to be massively ramped up, as a matter of routine. Making sure the contact tracing infrastructure is there, both in terms of the resources needed to do that, as well as any ancillary IT infrastructure.”

One day, perhaps Leung will address some of these topics in the lectures he gives to students on medicine and public health, medical ethics, humanitarianism, and palliative care.

In the meantime, there’s no question that applying one particular lesson from history could help lower the potential death toll from COVID-19.

“The precautionary note is very much reflective of the 1919 second wave of the 1918 (flu) pandemic, which actually killed a lot more people than the first wave,” Leung said. “That’s why we need to plan for the worst, and hope for the best.”


This article appeared in the Fall 2020 edition of Alumni Gazette