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Opinion | How Hong Kong can avert a fourth wave of Covid-19 infections

  • Studies show that infection transmission can vary widely depending on the primary setting. An understanding of the different risks involved would help policymakers maintain control even as containment measures are relaxed

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How Hong Kong can avert a fourth wave of Covid-19 infections
In this Covid-19 pandemic, understanding the transmission dynamics of infection is key to controlling it. Following our success in containing the second wave of infections originating from returning Hongkongers, social restrictions were relaxed in stages, but this was followed by another resurgence that reached alarming levels.
Resolute government decisions to impose correspondingly restrictive social-distancing measures have led to a gradual decline in local transmissions, from the peak of 149 cases of infections to single digits. Of greater significance than the number of infections was the incidence of chains of infection across different settings, most notably in bars, restaurants and eateries, markets, workplaces, places of worship, container terminals and homes for the elderly.

Understanding the variability of infection transmission, as inferred from global molecular epidemiological studies, is increasingly recognised as paramount to controlling the pandemic. Mathematical modelling estimated that 10 per cent of Covid-19 cases might have accounted for 80 per cent of transmissions worldwide. Studies in Hong Kong have also found that 20 per cent of cases were responsible for 80 per cent of local transmissions.

In Hong Kong, the largest cluster of 103 cases emerged from a bar-and-band setting. Globally, massive outbreaks have been reported from “superspreading events”, including mass religious gatherings and entertainment and sports events.

Understanding the risks for transmission in these clusters which could lead to large outbreak of infections is critical for maintaining control, as social-distancing measures are relaxed. The viral load or infectivity of the human source is one key determinant of transmission risk. The other is the type of setting in which cluster transmission takes place, which can be controlled.

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