Singapore has yet to detect any Covid-19 cases associated with the XE recombinant strain as at last Tuesday, the Ministry of Health (MOH) said.
This strain is a hybrid of the two predominant Omicron sub-variants, or strains: BA.1, otherwise known as the original Omicron strain, and BA.2.
The Straits Times answers some questions on it.
Q What is a recombinant strain?
A A Sars-CoV-2 recombinant strain emerges when one Sars-CoV-2 strain picks up some genetic material from another Sars-CoV-2 strain.
Besides XE, there are other BA.1-BA.2 recombinant variants, such as XR, XJ and XM.
Another previous recombinant variant known as "Deltacron" was a combination of the Omicron and Delta variants.
Q Should we be worried?
A A recombinant strain is not necessarily more dangerous.
In earlier reports, health experts said that there was no cause for panic as recombinant variants are a common feature of viruses, and that while they crop up quite frequently, they usually disappear on their own.
The World Health Organisation (WHO) also said that more due diligence is required before XE should be labelled as a variant of concern.
Q What strains are currently circulating in Singapore?
A MOH said the BA.1.1 strain used to be the predominant one until BA.2 became the predominant strain from February.
Since March 15, more than 98 per cent of local Covid-19 cases have been infected with the BA.2 sub-variant, MOH said.
"The Ministry of Health is constantly monitoring information about new strains and prevalence of circulating variants in the local community and will provide updates should there be significant developments," it said.
Q How did Omicron sub-variant BA.2 end up causing the vast majority of Singapore's recent Covid-19 cases?
A Preliminary studies suggest that BA.2 is more transmissible than BA.1, even though all the Omicron sub-variants are highly contagious.
However, the chances of becoming severely ill, being hospitalised or dying are significantly lower with the Omicron variant than the Delta or earlier variants.
So far, research indicates that BA.2 is no different from BA.1 in this regard.
Vaccination as well as infections from earlier Covid-19 variants have given many people a certain degree of immunity.
BA.2 does not seem to change what is currently known about the Omicron variant. It is known that Omicron is somewhat more likely than other variants to cause breakthrough infections of vaccinated people, which is one of the factors behind the surge in infection numbers to record highs.
However, Covid-19 vaccines do continue to provide substantial protection against infection, and especially against severe disease.
Booster shots make the protection even more robust.
Q Is Deltacron still a concern?
A There is no need to be worried and it is unlikely to represent a new phase of the pandemic. Based on reports, the gene that encodes Deltacron's surface protein - known as the spike protein - comes almost entirely from Omicron. The rest of the genome is from Delta.
The Deltacron variant was first detected in Covid-19 samples collected in France in January, and has not been moved up the risk classification beyond a "variant under monitoring" by WHO since early last month.
The coronavirus' spike protein is the most important part when it comes to invading cells. The spike protein is also the main target of antibodies produced through infections and vaccination. This means the immunity that people have acquired against Omicron should still continue to work against Deltacron.