Singapore has seen an uptick in community cases 12 days into phase two of reopening the economy, which will be a concern if the trend continues, experts said.

More than ever, people need to be vigilant and cautious, despite a clear sense of "crisis fatigue", with many keen to return to their usual habits, said Professor Teo Yik Ying, dean of the National University of Singapore's Saw Swee Hock School of Public Health.

"This is when we need to be even more careful, when we collectively start to let down our guard," he told The Straits Times.

He stressed that the country is still very much in the midst of an outbreak and remains in Dorscon orange - signifying a disease situation with moderate to high public health impact.

This comes as cases soar worldwide, with over 10 million cases to date and many countries struggling with flare-ups as lockdowns are lifted.

"Globally the pandemic situation has only gotten worse, and not better," said Prof Teo on Sunday. "Certainly the situation in some countries looks like they are lifting lockdown even before they have properly contained their first wave of infections."

In Singapore, the number of new cases in the community has increased to an average of seven per day in the past week, from an average of four cases per day in the week before. The number of unlinked cases has doubled to four a day in the same period.

While the figures have been encouraging so far, with no significant spike in numbers, there is a long road ahead, said Associate Professor Josip Car, director of the Centre for Population Health Sciences at Nanyang Technological University's Lee Kong Chian School of Medicine, yesterday.

"The long-term impact of Covid-19... cannot and should not be underestimated; no one and no nation can afford to be complacent."

He emphasised the importance of scrutinising new unlinked community infections, which might indicate possible future trends the virus is taking; new clusters, as intermingling increases; and the profile of infected patients, which helps to identify at-risk groups.

Associate Professor Alex Cook, vice-dean of research at the Saw Swee Hock School of Public Health, said on Sunday that the country was now in a good position to handle any short-term resurgence in cases, given the low number of Covid-19 patients now needing critical care.

Noting that there had been no sustained upward trend so far, he said: "I'm very pleased with how the community cases have looked in June."

But phase two has not been without hiccups. The authorities have closed some outlets and meted out fines to those caught flouting the rules. All ActiveSG indoor sport halls were also closed on Sunday as a "time-out" after a Covid-19 patient and others played badminton in a large group - going against safe management measures. This suggests the need for more checks and enforcement, Prof Teo said.

"We should try to do better to identify such lapses in advance, and not wait until a case or, even worse, a super spreading event has occurred... As time passes, fatigue and hubris will set in... Checks and enforcement remind employers, operators and the public that we all need to continue to be on our guard."

Prof Car said such incidents will also teach the country how best to introduce more activities amid the pandemic, and whether Singapore can afford the potential risks such activities pose.