What the world learned from Sars stands us in good stead to curb Covid-19

Far from a gloomy observation, the fact Covid-19 behaves like Sars should give us hope. After all, we now know about how coronavirus infections cluster, where the hotspots are, and what public health measures are likely to prove effective

Anson Au

Published: 6:30am, 27 Feb 2020

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The Covid-19 epidemic sweeping through the Asia-Pacific appears to be heading inland towards Western Asia and Europe. This past week has witnessed the first major outbreaks outside the Asia-Pacific, in Iran and Italy, prompting temporary lockdowns on schools, museums, universities and cinemas, as well as bans on public gatherings.

With a climbing death toll and infections diffusing through the continent, Covid-19 takes on new meaning as it reopens the scars left by the severe acute respiratory syndrome, parallels that pundits have been eager to point out.

Yet, this comparison is our compass for navigating the way ahead. We have learned from Sars in ways that allow Hong Kong and other global cities to better prepare to curb the spread of Covid-19.

Cutting-edge network science research including the latest simulations over the past few weeks on the Covid-19 epidemic, as well as evidence on how Sars diffused in cities worldwide, help us to infer what to expect from Covid-19.

First, we can observe how and where respiratory viral epidemics are most likely to be transmitted. Sars revolutionised how we thought coronaviruses spread. Where before, our models assumed that everyone had an equal chance of getting infected, Sars showed that people have vastly unequal chances of infection because comparable coronaviruses tended to cluster.

The clustering patterns debunked the widespread myth that person-to-person contact on the streets was actually the most likely form of transmission. Disease transmission and contact rates are disproportionately higher in specific types of sites than anywhere else.

These hotspots are hospitals, which accounted for 50 per cent of Sars infections, and crowded residences occupied by a larger number of people who make contact on a regular basis, such as the Amoy Gardens complex in Hong Kong. At that private housing estate in Kowloon, more than 100 cases were reported in one block and experts concluded the killer virus had spread through sewage pipes outside the building, and water traps connected to bathroom floor drains.

For Covid-19, this clustering pattern is likely to be intensified because it has a low case-fatality rate of around 3 per cent. Coronaviruses with lower fatality rates are predisposed to spreading to a wider population because infected people have a greater likelihood of coming into contact with other people before the onset of serious symptoms.

To illustrate, Sars, which had a fatality rate of 10 per cent, and the Middle East respiratory syndrome (Mers), with a fatality rate of 34 per cent, each had progressively lower absolute numbers of cases, around 8,000 and 2,500 respectively – because serious symptoms manifested among infected people before they had a chance to spread the disease.

We are already beginning to see some of the same clustering patterns in Covid-19 that we did with Sars, which explains why the Diamond Princess cruise ship, for instance, was a hotbed of disease transmission. Knowing where and how Covid-19 is likely to cluster helps us know what prevention measures to devise and which sites to target.

As a result, secondly, we are better poised to assess the efficacy of different policy measures and what measures should be adopted. Much public discourse has centred on toughening up travel restrictions. However, the latest simulation models on Covid-19’s diffusion across different Asian countries show that the Wuhan travel ban itself will only be temporarily effective.

It delays the onset of transmission in international cities for weeks, but Covid-19 will pick up its growth afterwards from cases originating in places other than Wuhan.

Public health interventions and behavioural changes are where we should focus to curb the spread of Covid-19. We should implement mandatory prevention measures, such as setting up many more handwashing and hand-sanitising stations in hospitals, residential complexes, malls and restaurants.

Given that hospital resources are being stretched, we should also consider altering the way treatment is administered to reduce the number of fatal cases, such as prioritising patients with pre-existing conditions for treatment compared to other patients at the same level of disease progression or with similar symptoms.

For work and public policy, we should implement pre-quarantine measures more widely, such as permitting workers from as many sectors as possible to work from home or at a distance. Community organisations should also postpone community services and gatherings.

The jarring case of South Korea’s recent spike in infected cases, mostly tied to membership participation in services at a single organisation, the Shincheonji Church of Jesus, reminds us how important it is to reduce contact in large clusters.

Yet, hope remains. Many evocative parallels are drawn between Sars and Covid-19 to paint a portrait of gloom, but the same comparison actually highlights the ways in which governments in Hong Kong and worldwide have learned considerably from Sars. Public health measures have evolved drastically since 2003.

Entirely new public health research centres were created in the wake of Sars both locally, such as the School of Public Health at Hong Kong University, and in global cities abroad where Sars hit, such as the Dalla Lana School of Public Health at the University of Toronto.

The uptake of public health measures has been felt even in the Chinese government, which swiftly quarantined Wuhan, dispensed public updates, built impromptu hospitals, and shared genome sequences for Covid-19 early on, earning praise from leaders at the World Health Organisation.

We have learned, we are adapting and we will continue to perform better than we would have under our old ways.

Anson Au is a visiting professor in the School of Humanities, Social Science and Law at Harbin Institute of Technology and a PhD student in sociology at the University of Toronto

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