Study suggests testing, contact tracing and population behavioral changes can meaningfully control COVID-19 without resorting to a total lockdown that can have a more disruptive social and economic impact
No country has been able to beat the coronavirus as yet.
That said, Hong Kong appears to have averted a major COVID-19 outbreak up to March 31 by adopting far less drastic control measures than most other countries, reveals a new study published in The Lancet Public Health journal.
It did so with a combination of border entry restrictions, quarantine and isolation of cases and contacts, together with some degree of social distancing.
Tackling second wave ably
Hong Kong seems to be doing reasonably well even now. Right now, for instance, you can enter Hong Kong only if you’re already a resident. And even if you are, you’ll have to turn over your saliva for a coronavirus test.
This is one of the measures the Hong Kong government has adopted–including banning non-residents from entry, and giving tracking bracelets tied to an app to those arrivals who are allowed in.
All these are the new steps to try to control a small wave of new coronavirus cases that arose in recent weeks.
Hong Kong ordered bars and pubs to close for two weeks from 6pm local time on April 3, 2020. The measure came as the city stepped up social distancing rules to combat the coronavirus pandemic.
The Centre for Health Protection (CHP) of the Department of Health announced that as of 4pm on April 18, there were 1,023 confirmed cases and on probable case in Hong Kong.
Measures during the first wave helped
The Lancet study estimates that the rate at which the virus is transmitted has remained at approximately 1 in the eight weeks since early February (after public health measures were implemented from late January onwards), indicating the epidemic in Hong Kong is holding steady.
An effective reproductive number of 1 means that for every person who is infected, another one becomes infected. And as the first one recovers or dies, the second one replaces them.
At an effective reproductive number below 1, the epidemic will fade out; above 1, it will grow.
As of March 31, Hong Kong had 715 confirmed COVID-19 cases including 94 asymptomatic infections, and 4 deaths in a population of about 7.5 million.
“By quickly implementing public health measures, Hong Kong has demonstrated that COVID-19 transmission can be effectively contained without resorting to the highly disruptive complete lockdown adopted by China, the USA, and Western European countries,” says Professor Benjamin Cowling from the University of Hong Kong who led the research.
“Other governments can learn from the success of Hong Kong. If these measures and population responses can be sustained, while avoiding fatigue among the general population, they could substantially lessen the impact of a local COVID-19 epidemic.”
Intense surveillance worked
The control measures implemented in Hong Kong in late January included intense surveillance for infections, not only for incoming travellers, but also in the local community, with around 400 outpatients and 600 inpatients tested every day in early March.
Extensive efforts were also made to track down and quarantine all close contacts an infected person had seen two days before becoming ill, and holiday camps and newly built housing estates were repurposed into quarantine facilities.
Additionally, anyone crossing the border from mainland China, as well as travellers from infected countries, were required to undergo 14 days of quarantine at home or in designated facilities.
The government also deployed measures to encourage social distancing including flexible working arrangements and school closures, and many large-scale events were cancelled (figure 1).
Study methodology
In the study, researchers analysed data on laboratory-confirmed COVID-19 cases in Hong Kong between late January and 31 March, 2020, to estimate the daily effective reproductive number (Rt) for COVID-19, and changes in transmissibility over time.
Researchers also analysed influenza surveillance data in outpatients of all ages and influenza hospitalisations in children, as a proxy for changes in COVID-19 transmission–assuming a similar mode and efficiency of spread between influenza and COVID-19.
The researchers also conducted three cross-sectional telephone surveys among the general adult population (aged 18 and older) of Hong Kong. They did so to assess attitudes to COVID-19 and changes in behaviours on January 20-23 (1,008 respondents), February 11-14 (1,000), and March 10-13 (1,005).
Further analyses suggest that individual behaviours in the Hong Kong population have changed in response to COVID-19.
In the most recent (March) survey, 85% of respondents reported avoiding crowded places, and 99% reported wearing face masks when leaving home–up from 75% and 61% respectively from the first survey in January.
This compares to reported face mask use of around 79% in similar surveys during the SARS outbreak in 2003, and 10% during the influenza A (H1N1) pandemic in 2009. These changes in behaviour indicate the level of concern among the population about COVID-19, researchers say.
While unlinked COVID-19 cases–with no identified source of infection–have been detected in increasing numbers since early March, the Rt remains around 1 (figure 2).
Increases in these cases could be the result of imported infections, highlighting the importance of border control measures including careful monitoring of arriving travellers, and testing and tracing efforts to maintain suppression–although these measures will be increasingly difficult to implement as case numbers increase, researchers say.
Study limitations
The authors note some limitations in the study, including that while school closures can have considerable effects on influenza transmission, it is still not clear whether or how much children contract and spread COVID-19, so the role of school closures in reducing COVID-19 transmission is not known.
The authors also note that the major impact of control measures and behavioural changes on influenza transmission might not have a similar impact on COVID-19.
Finally, experience of avoidance behaviours was based on self-reported data and might have been affected by selection bias, away from adults who might have been working. However, surveys were also done in non-working hours to reduce this bias.
