News & Perspective

The importance of non-pharmaceutical interventions against COVID-19 and influenza in Hong Kong

Infectious Diseases
4 months ago, OP Editor

The COVID-19 outbreak is the most challenging widespread respiratory virus disease since the 1918 H1N1 influenza pandemic. As of May 4, 2020, Hong Kong had 1,040 reported cases of COVID-19, in a population of around 7.5 million. Given the absence of a COVID-19 vaccine, Hong Kong is at present adopting non-pharmaceutical interventions (NPIs) as an alternative approach towards the management of the COVID-19 pandemic.1 An observational study recently published in The Lancet Public Health, examined the impact of NPIs against COVID-19 transmission in Hong Kong.1

Hong Kong leveraged on their prior experience with the containment of severe acute respiratory syndrome (SARS) epidemic in 2003 to develop an effective strategy to control the COVID-19 outbreak. The SARS control measure consists mostly of tracing the source of infection, compulsory isolation, surveillance of contacts, and school closure.2

Notably, similar methods were adopted for the management of COVID-19. Primary measures implemented by Hong Kong to reduce local transmission of COVID-19 include two fundamental strategies: Suppression and mitigation. Initial suppression measures include intense surveillance for infections of both incoming travelers and the local population.1

In early March 2020, the Hong Kong Government tested approximately 400 outpatients and 600 inpatients. COVID-19 positive patients were isolated in the hospital until their viral loads were undetectable. Subsequently, contact tracing led to issuing quarantine orders to individuals who were in close contact with the population diagnosed with COVID-19 infections. Furthermore, travelers arriving from affected countries were imposed with quarantine orders. These individuals were isolated in specialized facilities such as holiday camps and newly constructed housing estates.1

Most importantly, mitigation strategies include social distancing, travel restrictions and bans, flexible work from home arrangements, school closures and cancelation of many events, such as conferences, religious services, and local gatherings.1

Recently, a study by Professor Benjamin J Cowling, WHO Collaborating Centre for Infectious Disease Epidemiology and Control at the School of Public Health, The University of Hong Kong, evaluated the importance of NPIs as health measures towards reducing the incidents of COVID-19 in Hong Kong.1 The primary purpose of this study was to quantify behavioral changes towards the transmission of both COVID-19 and influenza virus, given the shared similarity in infectivity mode and patterns.1,3

The information revealed that social distancing measures and changes in population behaviors in late January resulted in a significant decline in COVID-19 transmission. An estimated daily reproductive number (Rt) remained below 1 throughout February and early March. Moreover, school closures contributed to a marked reduction in COVID-19 cases, reflected in the decrease in Rt from 1.28 to 0.72.1,4

However, since early March, there has been an increase in unlinked COVID-19 cases due mainly to imported infection. Although the Rt value remained around the critical threshold of 1, travel measures and testing were essential for maintaining the suppression of COVID-19.

Behavioral changes in the Hong Kong population also played a key role. Results from three cross-sectional telephone surveys revealed that 71.1%, 92.5%, and 93.0% of the population reported washing their hands frequently; 61.3%, 90.2%, and 85.1% of individuals avoided crowded places; and 74.5%, 97.5%, and 98.8% of respondents wore masks when going out. In addition, surveys 2 and 3 reported that 88.0% and 83.8% of the population in Hong Kong preferred to stay at home.1,4

Following the analysis of surveys 2 and 3, 95.4% and 93.7% of respondents who were parents, agreed to school closure as a control measure for COVID-19 in Hong Kong. Due to school closure, 80.1% and 68.8% of the parents confirmed that their children had direct contact only with their household members.1,4

Similarly, a 33% decrease in transmissibility of influenza also occurred after school closure. The corresponding Rt calculated from influenza hospitalization data before school closure was 1.10 and subsequently declined to 0.73 after school closure.1,4

The outcomes of the study justified the benefits of NPIs in containing COVID-19 transmission. While the study was not able to identify the most effective NPIs, Prof. Cowling highlighted the significance of social distancing and behavioral changes by stating, “Our findings strongly suggest that social distancing and population behavioral changes have a social and economic impact that is less disruptive than total lockdown and is also able to meaningfully control COVID-19.”

In summary, the study illustrated the feasibility and effectiveness of Hong Kong’s strategy in reducing the spread of the COVID-19.

  1. Cowling B et al. Impact assessment of non-pharmaceutical interventions against coronavirus disease 2019 and influenza in Hong Kong: an observational study. Lancet Public Health. 2020.
  2. Hung L et al. The SARS epidemic in Hong Kong: what lessons have we learned? JRSM. 2003;96(8):374-378.
  3. Cowling B et al. Community Psychological and Behavioral Responses through the First Wave of the 2009 Influenza A(H1N1) Pandemic in Hong Kong. J Infect Dis. 2010;202(6):867-876.
  4. How Hong Kong contained COVID-19 without total lockdown. Science Media Centre Malaysia Accessed April 19, 2020.


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