The ambush-style lockdowns in Hong Kong are being criticised as a violation of human rights. However, such sudden lockdowns may remain the most efficient way for the city to control the spread of Covid-19 (“ Hong Kong’s latest lockdowns uncover four Covid-19 cases in three buildings ”, February 8). To know the reason for this, we must know the answer to two questions: why a lockdown, and why ambush-style. Lockdowns are the most effective way known for tracing or eliminating the virus infection chain. Since people are not moving, authorities or health care workers can more easily identify possible cases. As a result, all people within the lockdown district or housing block can be tested, or treated if needed. It ensures control over disease in a single location, making it harder for it to spread to other communities. Three lockdowns ordered; pregnant woman who evaded quarantine may face legal action As for the ambush style adopted , the lack of notice is the only way to ensure that no one can escape the lockdown. Some people in the lockdown district or block, including those most at risk of contagion due to their close relationship with infected patients, might choose to leave the place if they were given prior notice. If that happened, the lockdown would be meaningless, and at worst see potential patients spread the disease to people in other districts. Covid-19 will not disappear by itself. To eradicate the virus, we must take a step further, in exchange for a disease-free Hong Kong and to ease the pressure on the city’s already heavily burdened health care system. Eric Lee, Tai Po