Hong Kong rode out the first and second waves of the Covid-19 pandemic without a catastrophic outbreak because the government acted quickly and decisively to suppress contagion. Now, without a resolute display of a comparable sense of urgency, the city is at risk of being overtaken by a third wave. To head off a major outbreak, it may even prove time to consider reversing recent relaxation of some radical social-distancing measures. Fears of a new wave rose when 24 people returned preliminary positive tests , of which an extraordinarily high 19 were locally transmitted and linked to an elderly care home and two restaurants. This was a day after news of 14 new infections, including nine locally transmitted cases with similar links. Five that could not be traced added greatly to worries. The government has undertaken a fresh review of its coronavirus policies, after health minister Professor Sophia Chan Siu-chee had already unveiled a number of new measures. These include the requirement that domestic helpers return a negative test result before flying to the city and be quarantined in hotels for 14 days at their employers’ expense. Others include control of the flow of people returning from high-risk countries, virus tests for ships’ crews ahead of visits to the city, and deep throat saliva sampling for aircrew on arrival at the airport. These steps are the least to be expected, given that Dr Chuang Shuk-kwan, head of communicable diseases for the Centre for Health Protection, has expressed worries about a potential “massive community outbreak” implicit in so many sources of infection. The latest breakouts of the virus send a very loud wake-up call. Unless they are controlled, we stand to waste the sacrifice of months of social and economic shutdown that arguably saved us from a worst-case scenario that befell many countries. These new cases did not just come about this week. The victims were probably infected 10 to 14 days ago. The restaurants are potential hosts of super-spreaders. We should brace for more positive tests. Some will strongly debate the need for a sledgehammer approach. There are steps that can be taken without the reimposition of a general lockdown at a social and economic cost borne by the entire population. They include an intensified regime of testing, tracing, and tailored risk-mitigation measures, as with domestic helpers. An enhanced community-wide testing regime should involve coordination with the private sector facilitated by targeted subsidies to stimulate demand. Testing on its own will not stop the spread of the disease in its tracks. But at least, while other anti-infection measures are applied, it will instil a sense of awareness and shared responsibility for health and welfare.