The spike in Covid-19 cases globally is concerning, said public health experts who warned that the same resurgence of cases could happen here, if people are not cautious.

Australia, South Korea, Japan and Hong Kong are experiencing new waves of infections, despite having good health systems and robust strategies to combat the virus, they stressed.

Singapore's advantage is its strict enforcement measures, but the next few weeks could see case numbers rise as a result of crowds and poorer safe distancing during the general election period, as well as the reopening of cinemas and other local attractions.

Professor Teo Yik Ying, dean of the National University of Singapore's Saw Swee Hock School of Public Health, told The Straits Times: "As to whether it (resurgence in cases) will happen during these few weeks, we will have to wait and see. Singapore has much stricter enforcement of the rules around mask wearing, and I believe this may make the difference."

His colleague, Associate Professor Alex Cook, vice-dean of research at the school, said a concern was whether transmission rates would rise sharply as Singapore continues to gradually reopen its economy and allow for more work and social activities.

He said: "We can see the effects of this in other countries. When lockdowns end, the epidemic resurges, unless there are adequate measures such as mask wearing and contact tracing in place."

Covid-19 community cases here dropped to single digits by the end of the circuit breaker, which was lifted from June 2.

Since then, infections have risen gradually. As of Sunday, the number of new community cases had increased to an average of 16 per day in the past week, from an average of 10 cases per day in the week before.

The number of unlinked community cases also went up; from an average of five to eight cases a day in the same period.

On whether people should be concerned about reports of localised crowds during the recent general election, Prof Cook said: "It was a one-off event, so even if there were some additional risks from the voting process, the impact on the epidemic would be limited."

Infectious diseases expert Leong Hoe Nam, who expects a spike in cases in one to two weeks, said it would be "a miracle" if this did not happen.

"The virus is like a predator searching for the weakest link," Dr Leong cautioned, calling on Singaporeans to be more vigilant, avoid crowds and maintain safe distancing as much as possible.

With Covid-19 here to stay, a sustainable and effective testing strategy is paramount, the experts said.

Even as more tests are done, it is important to do so in a targeted way, to proactively pick up suspected infections, especially among those working on the front lines or those who have regular contact with a diverse and large number of people, Prof Teo said.

"Singapore can certainly increase the number of tests, so it is not a matter of capacity. I hope we can move towards both increasing testing capacity, and also the clever deployment of the available tests to perform forward surveillance, in addition to identifying the infected cases."

Forward surveillance, he explained, is to assess situations and circumstances, so that cases can be picked up early and possible outbreaks averted.

This includes, for example, the testing of sewage.

An example of efficient testing is to pool multiple samples from suspected cases into a single polymerase chain reaction (PCR) test.

"The strategies in the use of PCR tests are constantly evolving, and we have to identify the strategy that is most efficient and sustainable," Prof Teo said.

With the global situation remaining in a state of uncertainty and flux, Singapore should also tread cautiously when it comes to air travel, the experts added.

The country can cautiously open for business travel with specific countries which have adequately controlled the outbreak with strict measures, but mass market tourism which will involve a lot more traffic would be harder to regulate, Prof Teo explained.

Ultimately, Singaporeans will have to adapt to a new normal to keep the economy moving, with cases popping up here and there, and sudden periodic surges, Dr Leong said.

"We cannot expect zero cases. Look at Hong Kong and Beijing - even with a good mask culture, and an early lockdown, they still had spikes in cases," he said.