SINGAPORE - The multi-ministry task force tackling the Covid-19 pandemic has warned that an Omicron wave is imminent and that Singapore needs to be prepared.

Meanwhile, the daily number of new Covid-19 cases globally topped 1.6 million for the first time on Dec 29, and numbers have remained above a million a day since then. They crossed the two million mark on Wednesday and hit 2.5 million on Thursday (Jan 5 and 6).

Even though Omicron is believed to cause a much milder illness than Delta, some places seeing a surge in cases are finding their healthcare systems stretched to breaking point.

So where does Singapore stand today, and what can we expect in the coming months?

Health Minister Ong Ye Kung said Omicron now accounts for almost 20 per cent of all new community cases here, so it is likely to become the dominant strain in circulation fairly soon.

Covid-19 cases have been rising here, with more infections in the last three months of the year than the total number of people infected in the previous 20 months.

There were close to 100,000 infections here between the first case in January 2020 till the end of September 2021, with more than half the cases coming from the foreign worker dormitory outbreak that started in April 2020 .

But by year end, the number of people infected with Covid-19 had jumped to just under 280,000 cases - almost tripling in just three months. This was before the advent of Omicron and this number does not include people who are asymptomatic or are mildly ill but tested positive through self-administered antigen rapid tests.

The experts all agree that the year-end surge is the result of Singapore relaxing measures and opening up.

Associate Professor Alex Cook, vice-dean of research at the National University of Singapore's (NUS) Saw Swee Hock School of Public Health, said the upswing followed "the relaxation of social measures after National Day, which led to enough socialisation to push the R (reproduction) value above 1and spark the beginning of the wave".

"Then, when measures were tightened again, the epidemic continued to grow because of the switch to home-based isolation and quarantine, which is inherently more 'leaky' than institutional isolation measures," added Prof Cook.

Professor Leo Yee Sin, executive director of the National Centre for Infectious Diseases (NCID), said the surge in the last quarter "was largely contributed by the Delta variant which arrived in Singapore in April 2021".

This variant spreads far more easily than previous variants, she said, adding: "There is also a longer duration of viral shedding among the unvaccinated."

Prof Leo said that at the height of the spread, the effective reproduction number was estimated to be 1.4 - which means one infected person would spread the disease to 1.4 other people.

Infections started to fall last month as community immunity went up through a combination of high vaccine coverage and infection, as well as some tightening of safe measurement measures.

However, just as Singapore was getting a handle on Delta infections, Omicron is now in the community and experts foresee a tsunami of infections. The infection rate is again above 1 this week, indicating a growth in numbers.

Said Associate Professor Hsu Li Yang, an infectious diseases expert at the NUS' Saw Swee Hock School of Public Health: "I believe there will be an Omicron wave. We have started to see the beginnings of this here, and nearly every country so far has had a similar experience once Omicron started spreading in the community."

Prof Leo added: "Many affected regions have reported a sharp increase in cases, higher risk of reinfection, and vaccine breakthrough. Despite high local vaccine coverage, we anticipate likewise that we will experience a sharp rise of cases."

This is because the Omicron variant "is even more transmissible than the Delta variant, has a shorter incubation period, and quicker doubling time of around two to three days", she explained.

Said Prof Cook: "Probably, once Omicron is really established, we'll see another wave, as other countries are experiencing. However, because most of our immune systems have been primed by vaccination, or even infection, this might not lead to a similarly large wave of severe cases."

Prof Hsu agrees that while there might be a surge in cases, it will be different from the Delta wave, without hospitalisations and deaths surging in tandem.

Associate Professor David Allen, an infectious diseases expert at NUS, also says that an Omicron wave is likely to result in fewer cases of serious illness. And if it has less impact on the healthcare system, Singapore will likely see further relaxation of measures.

He added: "If and when there are spikes in cases requiring hospitalisations, the population will alter their behaviour to decrease risk and the Government will slow the step-wise relaxation (or consider a brief period of a moderate increase) of measures - both of which independently will lead to a drop in cases."

According to international data, the Omicron variant does not appear to infiltrate and do damage to the lungs, unlike earlier variants where many seriously ill patients required oxygen supplementation.

Said Prof Leo: "So while we brace ourselves for a sharp and ferocious Omicron wave, we hope that it will cause less lung damage where many may require mechanical oxygen support in intensive care."

Minister Ong said at the press conference on Jan 5 that Singapore has seen a total of 2,252 cases, of which three required oxygen supplementation.

"All have been taken off oxygen within three days. So all three are now recovering. None has required ICU (intensive care unit) care as yet. So, if these same 2,252 infections had been caused by Delta, based on our experience, we would expect about 30 individuals to require oxygen supplementation, ICU or die."

But the vast majority of these Omicron cases are vaccinated travellers, who tend to be younger and healthier than the local cohort hospitalised with the Delta variant.

Prof Leo is concerned about Omicron's effect on older people and those with underlying medical conditions, especially if they are unvaccinated, since the majority of cases reported so far are in younger people, those who have been vaccinated or have had prior infections.

While more data is urgently needed, she said early observations suggest that although vaccines appear less effective at preventing infection, "the effectiveness against severe illness appears relatively less affected".

But there are still 38,000 seniors in Singapore who remain unvaccinated.

Another possible piece of good news is that reinfection appears to be a one-way road with people previously infected remaining at risk of getting Omicron. But those infected with Omicron appear relatively immune to earlier variants.

Said Prof Leo: "Some early data suggested that Omicron cases have neutralisation ability against Delta and that will likely prevent infection in the reverse direction. It is too early to determine whether Omicron would be a milestone towards virus attenuation and broaden neutralising ability."

So what does the rest of the year hold in store?

There will be no changes before Chinese New Year next month. But beyond that, things might start looking up.

Prof Cook said: "Obviously we can't foretell the emergence of new variants, especially curveballs like Omicron, and whether they will set us back further on the return to normalcy.

"Singapore's high vaccination rates and growing booster rates position us well for the Omicron wave and we ought not to be overly cautious about reopening."

Prof Allen expects that travel restrictions will gradually decrease in the coming months and the size of gatherings will increase step-wise, though masks will still be routinely worn.

Prof Hsu also expects to see more people travelling. He said: "There may be more new variants of Covid-19, but probably no new variants of concern as alarming as the Delta variant."

As the economy opens and normal travel resumes, Prof Leo urged everyone to continue taking personal responsibility because the steps taken to prevent Covid-19 have helped reduce respiratory illnesses as a whole. "Good habits borne out of Covid-19 are to be kept and not just hard-wired into policies or law," she said.