It would seem the fourth wave of outbreaks has finally arrived, with at least 20 preliminary Covid-19 infections of different origin detected across the city yesterday. The situation, as officials say, is highly worrying. Adding to the challenge is the travel bubble and the return of Hongkongers from the mainland under a new quarantine-free policy next week. The need to stay vigilant has never been higher. The government should not rule out tightening restrictions further in light of the circumstances. With nearly 9,000 citizens registered for the Return2HK scheme on the first day, the potential risk cannot be dismissed. Under it, Hongkongers with negative test results returning from the mainland and Macau need not spend 14 days in quarantine on arrival. The government is reportedly considering extending the same travel convenience to non-residents. Given the situation across the border is relatively stable, health risks are considered to be relatively low. But this does not mean we should lower our guard. After all, the summer outbreak was said to have stemmed from loopholes in quarantine exemptions for aircrew and seafarers. The demand from the public wanting to cross into the mainland appears to be just as high. The city’s four community Covid-19 test centres have drawn crowds over the past few days, with many keen to resume their routines across the border. Separately, the travel bubble that enables locals and Singaporeans to travel without quarantine is only days away. It would be wise to closely monitor the situation before further extending such exemptions. Compared to the United States and Europe, Hong Kong had fared reasonably well in curbing the epidemic until the third wave hit in the summer. Residents’ return scheme opens as Hong Kong confirms nine new Covid-19 cases Daily life for most people is now by and large back to normal, and the easing of restrictions may partly explain why the trend in infections is worsening again. The wide range of government responses to the epidemic, the latest being restrictions on staycations and visits to hotels used for those still in quarantine, underlines the need to make necessary changes. It would not be surprising to see social-distancing rules tightened again. Likewise, adjustments to cross-border travel may also be necessary in light of the latest circumstances.