The recent sharp resurgence in local infected cases has again pushed the normalisation of life and business in Hong Kong beyond reach. The cluster outbreak of unknown origins in densely populated parts of the city is particularly alarming. Classes are suspended again while social distancing measures get tightened again. What next? Covid-19 has clearly accelerated its spread in the community, making an exponential increase of local case count very likely in the coming weeks. Seven million citizens have not seen their government take decisive action, though, other than resorting to its old, small policy toolkit of social distancing , travel bans and dissuasion. Making public policy in Hong Kong is never easy. Declining trust in government and rising community defiance have made it even tougher since the rise in protest movements last year. From a strategic point of view, Hong Kong’s response to the pandemic is constrained by its low testing capacity . When a pandemic begins, the ideal response for government authorities is to begin testing early because it enables rapid identification of cases, quick treatment for infected patients and immediate isolation to prevent further spread. However, ordinary testing of suspected cases is no longer sufficient. Numerous asymptomatic carriers can easily spread the virus unwittingly, igniting outbreaks in their wake. Instead of waiting for all infected individuals to voluntarily seek care and be discovered, or the virus to die out – neither of which is likely to happen – some forms of mass testing have become imperative in Hong Kong. This is the practice of South Korea, Germany, Iceland and some cities on the mainland, all of which have tested a significant proportion of their population. Badly hit by the outbreak, France is about to launch a large-scale testing of those who live close to Covid-19 risk zones and identify asymptomatic individuals. South Korea has been relatively successful in containing the pandemic as it has significantly curtailed large community outbreaks without extreme interventions such as aggressive lockdowns. Widespread preventive testing in the community helped the government quickly isolate and treat infected patients, some of whom were asymptomatic. Changes in your voice could reveal if you have the coronavirus Reports suggest that as of June 30, around 1.27 million tests had been conducted in South Korea. Innovative drive-through and walk-through test kiosks were installed to facilitate mass testing. In the aftermath of the outbreak in Wuhan, Hubei, the local government there performed citywide testing of all residents. It found a small number of asymptomatic patients and ruled out the possibility of subsequent outbreaks. Similar large-scale testing was also conducted in Beijing from mid-June. While mass testing appears to be an appropriate solution for Hong Kong in light of the recent resurgence in cases, testing capacity is low – a maximum of around 7,000 tests per day. Government and private clinical laboratories together are far from able to conduct testing at meaningful scales. Given the constraints, it is perhaps a good idea to seek help from the mainland, which has excess capacity. Reports suggest Beijing has a daily capacity of more than 230,000 nucleic acid tests. Neighbouring Shenzhen alone can perform more than 10,000 tests per day, far exceeding Hong Kong’s capacity. Hong Kong could launch a larger-scale testing campaign with significant resources from across the border. What does a ‘third wave’ of Covid-19 infections mean for life in Hong Kong? Testing the whole population at frequent intervals is expensive, impractical and difficult to achieve. Instead, Hong Kong’s government should focus on targeted, complete and rapid turnaround testing for key groups such as taxi drivers, flight crews, nursing home residents and carers, restaurant workers, border control staff and public transport workers. If the local outbreak escalates, compulsory residence-based testing may become necessary, given that public housing estates have been heavily hit. As per the practice in Beijing and South Korea, the government could consider converting open-door public facilities such as sport stadiums into temporary testing stations . Additional voluntary testing programme could be introduced for low-risk groups on a self-paying basis or through government vouchers. Social distancing alone is evidently unable to contain the new outbreak in Hong Kong. Before the spread gets out of hand, the Hong Kong government must stop shying away from launching a mass testing campaign. Alex He Jingwei is associate professor at the Department of Asian and Policy Studies, The Education University of Hong Kong. He specialises in health policy and welfare governance