Reacting quickly to outbreaks of Covid-19 is key to stopping its spread. China’s success in seeing off the disease has been evident in the western city of Kashgar in the Xinjiang Uygur autonomous region with mass testing of 4.7 million residents and the quarantining of scores of identified cases, all in a matter of days. The flare-up is now claimed to be under control, but there are uncertainties as to its origin and an unusually high proportion of asymptomatic patients raises further questions. It is further proof that while much is known about the coronavirus, there is still a deal to be learned. Beijing’s strictly enforced Covid-19 measures ensure affected communities can quickly return to normal life. While most of the world is still battling the pandemic with surging numbers of cases and economies suffering, China’s cities are bustling. In the wake of the outbreak that began when a 17-year-old girl who worked in a garment factory tested positive, Kashgar was in lockdown. But prompt tracing and testing quickly identified those afflicted and at risk and the city was able to reopen. China’s scientific and medical prowess has enabled effective preventive strategies and put it in the forefront of development of treatments and vaccines. Further timely response by authorities was on show recently after scientists, while tracing the source of an outbreak in the northeastern port city of Qingdao, found live samples of the virus on imported packets of frozen cod and determined it could be infectious. Authorities have reacted promptly; the State Council has issued technical guidance aimed at plugging a perceived loophole by requiring cold chain products shipped from high-risk regions to have outer packaging disinfected and for health checks and registration of people handling them Questions abound about the high number of asymptomatic cases found in Kashgar with speculation that there could be a new Covid-19 strain or that those who have tested positive could yet develop symptoms. The finding adds to a list of unknowns about the disease that casts doubt on how effective a vaccine will be, should one that is safe and has proven efficacy be developed. Among the findings of recent studies are that one in five asymptomatic cases can still spread the virus and that the virus can, in certain conditions, stay on common surfaces for as long as 28 days. What Covid-19 immunity means and how long it lasts are still unclear. What we do know is that effective protection lies in wearing face masks, frequent washing and sanitising of hands and surfaces, and social distancing. Coupled with swift tracing, testing, quarantining and treatment, communities can remain safe while further research is carried out with an eye on eventually banishing the virus or at the least, keeping it at bay.