The Covid-19 infection clusters at two Hong Kong wet markets have not just sounded the alarm bell for many who regularly patronise such outlets. They may further strain the public health care system if the premises become breeding grounds for a wider outbreak. While an investigation is being carried out expeditiously, environmental and personal hygiene must also be stepped up with the same sense of urgency to help curb transmission. The situation is a disturbing reminder of similar outbreaks in Wuhan and Beijing during the initial stage of the pandemic. Here, at least seven cases are linked to fish stalls in the To Kwa Wan and Hung Hom markets, the latter of which also saw 10 infections involving cleaners and workers at frozen meat and dry goods stores earlier. Several possible ways of transmission have been suggested, including poor hygiene or fishmongers gathering inside the complex during rest periods. It is believed that the new coronavirus can survive on icy surfaces for days. The risk is further compounded by contaminated money changing hands between stall keepers and customers, as few wet markets have installed cashless payment systems. The closure of the two markets for sanitisation is a right response amid growing worries over the resurgence of local infections. Some wet markets have suffered a 20-30 per cent drop in business as a result. While some market-goers have stepped up precautions, such as avoiding direct contact with cash when receiving change, it is business as usual for others. The risk is real and vigilance is key. Call for ‘quantum leap’ in bat virus research to avoid new pandemic The fall to double-digit new infections each day this week is no cause for complacency. Given that mitigation measures take time to be effective, we are still far from the 17-day stretch of zero local cases a month ago. If there is any good news, it would be the fact that the ongoing tests of environmental samples from the two wet markets have so far been negative. But as cautioned by a leading microbiologist, wet markets are indeed a common source of infections. With at least 11 of the 73 government-run outlets having recorded infections, extra vigilance is needed for those who visit wet markets or work there. The authorities must not rule out further action if the outbreak spreads.