Testing is an essential part of Hong Kong’s strategy to halt the spread of the novel coronavirus. With thousands of new daily cases and an alarming rise in the number of deaths as a fifth wave of the disease rampages across the city, quickly screening people who may have had contact with those confirmed as being infected is crucial. That is especially so with the highly transmissible Omicron variant driving the surge, many of those affected not even knowing they are carrying the disease and capable of passing it to others. Stopping the strain in its tracks requires everyone being tested. Chief Executive Carrie Lam Cheng Yuet-ngor on Tuesday laid out how that is to be achieved, the compulsory process starting next month. With an eye on three rounds of testing for each resident, daily capacity for screening and sample analysis will be boosted to about 1 million a day. Most social-distancing measures will be extended to the middle or end of April. School holidays scheduled for July and August will be brought forward to March and April, enabling smoother testing for children. Land is being identified for construction of temporary treatment and isolation facilities and buildings converted to make them suitable for quarantining. A citywide lockdown has been dismissed and understandably so – the logistics of screening and providing for the food and medical needs of every resident in so cramped and crowded a city for the day or more for each round of testing is too challenging. Instead, authorities have opted for an online booking system with those required to test being determined by their Hong Kong identity card information. Lam warned of tough penalties for people who do not comply, being mindful that mass screening will not detect hidden transmission chains unless everyone participates. Hong Kong for now lacks the personnel and facilities for robust mass screening. Existing testing centres and laboratories are already overwhelmed by the surge in cases and hospitals are also struggling to cope with the explosion in patient numbers. Mass screening would require thousands more trained people to take and analyse samples. The mainland’s expertise is essential and its teams of experts and skilled workers have thankfully already started arriving. Testing times, but Hong Kong needs a Covid-19 strategy that is sustainable Controlling Covid-19, and especially a variant like Omicron that has many asymptomatic carriers or people who have little or no apparent infection, depends on finding cases before the virus can be passed on. The rapid antigen test kits authorities are distributing will alert those with positive results to avoid activities that put others at risk and confirm whether they have the disease through accurate PCR tests. But only after large-scale screening will Hong Kong have a complete picture of the threat. At last, a strategy has been laid out.