Experts warn that restrictions may have to be reimposed if the "exuberance" of the first weekend of phase two of the post-circuit breaker reopening continues.
In the light of second waves of Covid-19 infection seen in other countries that have eased lockdown measures, experts have expressed concern over the way people have been going out and about since last Friday, behaving as though the pandemic is over.
It is definitely not yet safe for people to mix and mingle, experts whom The Straits Times spoke to emphasised.
Professor Dale Fisher, who chairs infection control at the National University Hospital, had noticed the crowding at some places.
He said: "New clusters will appear very quickly with the lack of distancing I noticed. Exuberance is natural, but the community needs to not crowd."
"Deeply concerned" about the reported crowding, Professor Teo Yik Ying, dean of the National University of Singapore's (NUS) Saw Swee Hock School of Public Health, said: "The public is behaving as if the outbreak no longer exists.
"While it is understandable that people want to return to some degree of normalcy in their lives, the reality is there is a much higher risk of being infected when people mingle in crowds."
He added that should such crowding continue this week and the number of infections rises, restrictions may have to be reimposed.
Other countries that have eased lockdowns have seen new clusters emerging - such as at the market in Beijing and nightspots in South Korea - and had to quickly reimpose strict measures to prevent the resurgence of Covid-19.
Associate Professor Hsu Li Yang, an infectious diseases expert and epidemiologist at the school, said the crowding "could potentially lead to a rise in community cases in a week or two".
Many people see the outbreak here as being predominantly in the foreign worker dormitories, with very low numbers in the community, and so see little danger to themselves, especially if they continue wearing masks when out.
But the experts also stressed that wearing masks does not mean people are protected from getting infected by the coronavirus.
Dr Asok Kurup, an infectious diseases doctor in private practice, said: "I do not think that wearing masks alone is a panacea. It may give a false sense of security - hence the pockets of crowds."
Masks can reduce the viral load transmitted by someone who is infected, but do not stop the virus from being breathed in, as the virus is small enough to pass through porous masks such as the fabric ones that most people wear.
Prof Fisher said masks do help reduce transmission, but the best way to prevent large clusters of infections is by avoiding crowds.
He said that even though restrictions have been lifted, "it is better to stay home, but if you need to go out, then well-ventilated and uncrowded places are best".
Prof Teo was in full agreement. He said: "Mask wearing is a poor substitute for safe distancing and staying home unless necessary.
"It is important to remember that going out is a privilege that we shouldn't try to abuse, and mask wearing is what we have to do as a last resort. The first resort must still be to stay home if possible, or to practise safe distancing."
This is because the authorities are identifying people who are infected through their surveillance testing - indicating that there are people out in the community who have and are still spreading the disease, but do not feel sick enough to seek medical care.
They form hidden reservoirs of the virus that can erupt as people interact more freely with one another.
The situation in the community today reflects what happened here in February - before the explosion of cases in the dormitories - when a handful of cases led to many more due to people gathering in large groups, such as the large Safra Jurong cluster emerging from a dinner.
Prof Teo had previously warned that although the authorities have said people may meet in groups of five, it does not mean that "they can take advantage of this and start to meet multiple disparate groups of people" as such actions will clearly increase the person's risk of being infected.
Dr Kurup's advice is to be "less of a social animal" at this time and not to "have multiple dining sessions with different groups on consecutive days".
Companies, too, are encouraged to have employees work from home where possible, to reduce interaction among staff as well as to keep travel on public transport down.
Every bit of social distancing helps. Associate Professor Alex Cook, vice-dean of research at NUS' Saw Swee Hock School of Public Health, said: "People might think that a bit of transmission is okay as long as it doesn't threaten the health system. That is not entirely true and is a dangerous train of thought."
In countries like the United States and India, the easing of measures has resulted in thousands of new cases a day - more than 26,000 in the US and 15,000 in India on Sunday alone - and 267 deaths in the US and 426 in India the same day.
All the experts are confident that the Singapore authorities will not allow any resurgence of cases to overwhelm the healthcare system, which will result in more deaths.
Keeping the numbers low so all patients can get the best care possible could spell the difference between life and death for patients who get more severe illness requiring intensive care.
"If the healthcare system cannot cope with the number of people needing intensive care, then the number of deaths could rise precipitously," said Prof Cook, adding that the risk extends to the infected person's family and friends.
So far, 26 people here have died from Covid-19, out of more than 42,000 who have been infected.
Prof Cook said: "The low number of deaths so far does not mean this is a trivial disease; it just means we are lucky that so many cases were in fit, young men."
The million or more people in the population who are older people or have underlying medical conditions such as heart disease or cancer are at higher risk of severe illness.
Even people who have recovered from Covid-19 may face longer-term repercussions on their health, and at least a few have died from lingering effects of the illness, such as damage to their organs or clots in their blood.
Dr Kurup said any rise in unlinked community cases or new community clusters will be telling, and appropriate measures will have to be taken again before healthcare systems are challenged.
Prof Fisher said: "We can tolerate small clusters, especially if they are linked to each other.
"If the healthcare system is threatened, I am sure social restrictions would again be rapidly reimplemented. Singapore knows exactly how to prevent being overwhelmed, and I can't see that happening."
Prof Cook agreed. "I don't think it will threaten the healthcare system because we will be back in lockdown before that happens."
But how people behave in the coming days and weeks will decide if the greater freedom of movement allowed under phase two of the reopening will continue, or be curtailed to prevent a major spike in cases and deaths.
Greater cooperation from everyone will mean a better and freer life for all, though nowhere near a return to the pre-Covid status quo.
Re-emphasising the need to "rein in the crowds where feasible, however challenging", Dr Kurup said: "It is not, and should not be, life as before."