Unnervingly nicknamed Deltacron, the strain is a hybrid of the Delta and Omicron variants that have caused huge waves of infection around the globe.

Experts, however, stress the variant does not necessarily pose any additional threat.

While researchers are still looking into its characteristics, the prevailing view is that it is something to watch, not a reason to panic.

Here are five things to know.

What exactly is Deltacron?

Deltacron is a combination or “recombinant” of two variants of Covid-19, delta and omicron.

Scientists say its emergence is no surprise.

The World Health Organization (WHO) explains that recombination happens when two viruses infect the same person or animal, which leads to an exchange of genetic information and the emergence of a new variant.

When multiple variants circulate simultaneously and widely, like Delta and Omicron did, recombination is to be expected.

The new variant has been dubbed Deltacron, or Deltamicron, mainly by the media.

Some scientists insist it is inappropriate to use such terms, which sound much scarier than the variant is likely to be in reality.

WHO says it is “aware” of the recombinant, which combines the delta AY.4 and omicron BA.1 strains.

But it has not adopted a formal name for it.

Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security, told Nikkei Asia in an email: “There’s not enough information on cases, or virologically, to know what traits recombinant Delta/Omicron possesses. Because these recombinant forms differ in their recombination, the term Deltacron doesn’t make sense (except as clickbait). Which genes are recombined differs in these hybrids.”

Where has it been detected so far?

A recombinant of Delta and Omicron was discovered in January by Cypriot researchers.

News of a supposed “super variant” spread rapidly.

But scientists were quick to downplay it.

Some argued that it was not a new variant at all, but simply the result of laboratory contamination.

Krutika Kuppalli, a member of WHO’s Covid-19 technical team, tweeted at the time that “there is no such thing as #Deltacron”, saying it was likely a “sequencing artifact” after Omicron fragments ended up in a Delta specimen.

However, a small number of recombinant cases have continued to turn up, from Europe to the Americas.

This week in Brazil, the governments of two northern states informed the health ministry that they had found cases of Deltacron.

According to local media, a 34-year-old man and a 26-year-old woman were infected.

The ministry’s investigation, however, appeared to find that at least one of the cases was not Deltacron but rather a “co-infection” by Omicron and Delta, Brazilian media said yesterday.

The investigation is ongoing.

According to Gisaid, an international database of Covid-19 genomic information, the hybrid variant has cropped up in France, Denmark, Germany, Holland and Belgium.

As of this week, France had found the highest number of cases, 38, followed by Denmark, with eight.

Cases had yet to be reported in Asia.

A paper suggesting that at least two cases have been found in the US was released on medRxiv, a website that publishes pre-peer-reviewed medical papers.

How worrying is it?

Not very, at least for now.

While WHO was quick to label Omicron a “variant of concern”, indicating a possible increase in transmissibility or virulence, or a decrease in vaccine effectiveness, it has yet to list the recombinant as even a “variant of interest”.

It is currently a “variant under monitoring”.

This group is reserved for strains showing “genetic changes that are suspected to affect virus characteristics with some indication that it may pose a future risk,” but for which evidence of the epidemiological impact is “currently unclear”.

Maria Van Kerkhove, WHO’s technical lead, stressed in a March 9 briefing that it had been detected only at “very low levels”.

“We have not seen any change in the epidemiology with this recombinant, we haven’t seen any change in severity, but there are many studies that are underway,” she added.

ajid Javid, the UK’s health secretary, said the new variant is “not of particular concern” during an appearance on the BBC.

He explained that Omicron was still the dominant strain in the country.

In the Philippines, where Covid-19 infections have plunged, infectious diseases specialist Rontgene Solante was doubtful the variant would have much impact.

“The information regarding the combination of Delta and Omicron is not yet substantial, but I believe that a combination will not affect much and will not increase its virulence,” he told a press briefing, according to local media.

Still, health experts say there is much to learn about the hybrid, and emphasise that Covid-19 itself remains a danger.

“We have known that recombinant events can occur, in humans or animals, with multiple circulating variants of #SARSCoV2,” tweeted Soumya Swaminathan, chief scientist at the WHO. “Need to wait for experiments to determine the properties of this virus.”

Will vaccines work against it?

With so few known cases, it remains unclear how effective vaccines would be against the new variant.

But scientists say they should work to an extent.

Thomas Peacock, a research associate at Imperial College London, tweeted that “current vaccines work mostly by generating antibody response” against the virus’s spike protein.

“In nearly all these recombinants the spike is taken from a single virus so don’t expect any/much difference from the strain (the) spike is taken from.”

Johns Hopkins’ Adalja agreed.

“I expect vaccines would be able to perform just as they have against Omicron, since the virus is a hybrid that has the spike protein from Omicron, to which vaccines are partially effective.”

In general, people who are unvaccinated or who have had only one dose tend to be at higher risk of serious illness or death than those who are fully inoculated.

The same is likely to be true when dealing with new variants.

Experts say it is especially important for older individuals, or those with existing medical conditions, to be vaccinated.

Pfizer, meanwhile, has said that a fourth dose of its vaccine will be necessary.

CEO Albert Bourla said in a recent US TV interview that his company was working on a vaccine that would protect against “all variants”, including Omicron, and remain effective for at least a year.

Do we need lockdowns to protect populations?

At this time, scientists and governments do not appear to be considering lockdowns in response to the new variant.

Speaking in general terms, WHO’s Van Kerkhove said that “we cannot allow (Covid-19) to spread at such an intense level”.

But she added that this “doesn’t mean locking people down, locking people in their homes. It means using simple tools in a layered approach”.

Countries that continue to insist on “zero Covid” strategies – China being the leading example – may continue to find lockdowns necessary.

China has imposed tight restrictions in cities including Shenzhen, Shanghai and Changchun to stamp out nascent outbreaks.

Irwin Redlener, founding director at the National Center for Disaster Preparedness in the US, told MSNBC that China was dealing not with Deltacron but with another variant of omicron, BA.2, sometimes referred to as “stealth Omicron”.

That nickname, too, is now considered something of an ominous misnomer.

Initially, it was difficult to tell the variant apart from Delta on positive PCR tests.

But now that Delta is rarer, it is easy to distinguish Omicron BA.1 and BA.2.

While researchers warn against hyping up virus mutations and stoking public fear, they also say it is crucial to keep an eye on how variants evolve.

WHO insists that a very strong, worldwide surveillance system for Covid-19 is necessary to guard against emerging threats.