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Knowing the origin of omicron can help us understand how long this pandemic will last and where other variants lurk. Omicron is in at least 77 countries.

How did omicron evolve for over a year without our noticing? Researchers have three theories.

Researchers around the world are busy trying to identify the specific characteristics of the omicron variant of coronavirus and its origin — its viral heritage, if you like.

That may sound academic. But knowing that will help scientists get a better understanding of when this pandemic might end and how we can best protect ourselves against future variants of the virus.

There's not a lot of data (at time of writing), but we do know that omicron is dangerous.

It is spreading fast, internationally. On December 14, 2021, the World Health Organization said 77 countries had reported omicron cases.

The variant has more than 50 mutations, with a majority of them in the virus' spike protein, which it uses to infect human cells.

Existing vaccines are less effective against omicron. Even vaccinated people can get infected with it. It can "evade" or escape our immune response.

The variant appears to be more infectious or transmissible than other variants of coronavirus, and some experts are concerned that many more infections in a short space of time may push health systems beyond their limits.

It's possible to have a severe infection with omicron — the WHO has warned against thinking it is milder than other variants. Some omicron patients are already being treated in hospitals. And the UK reported the first person to die with omicron.

The UK has raised its coronavirus alert level with the number of omicron infections increasing rapidly

That's why it's so important to get first, second and booster vaccines. Experts say omicron is likely to continue spreading quickly and may soon supersede delta, which currently remains the dominant variant in many parts of the world.

We're unlikely to eradicate the world of this novel coronavirus in the near future.

SARS-CoV-2 is more likely to become endemic. That's when a virus is no longer a worldwide pandemic, but one that crops up from time to time, locally, such as the seasonal, common flu. We protect ourselves against influenza with an annual flu jab and we may then do the same with COVID.

Scientists say the sudden emergence of omicron is interesting because the variant seems to have evolved in parallel to other variants — that is, it's not necessarily a straight evolution of the alpha, beta, gamma and delta variants.

That's one possible reason why omicron is so different from the other variants, and why it will probably be hard to predict its next evolution. That's according to Emma Hodcroft, a virologist at the University of Bern, who spoke to DW's COVID-19 Special.

Sequencing information hosted by the international "Nextstrain" database suggests that omicron may have started its progression in mid-2020 — and we still didn't see it coming.  

Researchers have so far come up with three theories to explain how "weird" omicron evolved.

Farmers culled millions of minks in Denmark in 2020 when they were diagnosed with a mutated version of the coronavirus

It's possible that omicron evolved in a population of living people among whom the virus had circulated for some time. Those people may have become infected and recovered without its being detected or diagnosed, and without any testing or sequencing of the strain of the virus that had infected them.

Christian Drosten, a virologist at Charité University Hospital in Berlin, told Science magazine that he thinks omicron "evolved not in South Africa, where a lot of sequencing is going on, but somewhere else in southern Africa during the winter wave. There were a lot of infections going on for a long time and for this kind of virus to evolve you really need a huge evolutionary pressure."

But Andrew Rambaut at the University of Edinburgh is not convinced. He told Science: "I'm not sure there's really anywhere in the world that is isolated enough for this sort of virus to transmit for that length of time without it emerging in various places."

It's possible that omicron developed in a person whose natural immunity was suppressed, such as someone who was chronically ill or whose medication weakened their immune system.

That could be someone with a form of cancer or HIV. A suppressed immune system needs longer to fight viral infections. That in turn gives the virus more time to evolve and mutate in order to evade the person's immune response and defense.

Richard Lessells, an infectious disease researcher at the University of KwaZulu-Natal, supports this theory.

Lessells cites a young woman in South Africa who had an untreated HIV infection and carried SARS-CoV-2 for more than 6 months.

Science quotes him as saying: "The virus accumulated many of the same changes seen in variants of concern, a pattern also seen in another patient whose SARS-Cov-2 infection persisted even longer."

But Drosten says there's clear evidence, observed in people with HIV when they fight other viruses like influenza, to counter the theory. Drosten told Science that while those viruses developed mutations to evade the person's immune response, they also evolved to reduce their ability to transmit from person-to-person.

And compared to other coronavirus variants, omicron is significantly more infectious.

It is also possible that the virus hid itself in an animal host, evolved into omicron, and then transmitted back to a human host. 

Kristian Andersen, an infectious disease researcher at Scripps Research, and evolutionary biologist Mike Worobey of the University of Arizona, Tucson, support that theory.

The theory is further supported by the fact that we know that animals are susceptible to coronaviruses, such as SARS-CoV-2.

That's also why many researchers still believe that the first version of SARS-CoV-2, detected in Wuhan, China, over two years ago, originated in an animal.

In 2020, farmers had to cull millions of minks when a mutated version of the coronavirus was detected among them. Veterinary experts suspect the virus jumped from humans to the minks. There were then concerns that the "mink mutation" could jump back to humans again.

Experts say the virus experiences a totally different evolutionary pressure in animals (compared to human-animals) and that that could explain some of the unique mutations found in the omicron variant.

This article was translated from German

That's how to do it: If humans have COVID-19, dogs had better cuddle with their stuffed animals. Researchers from Utrecht in the Netherlands took nasal swabs and blood samples from 48 cats and 54 dogs in 2021 whose owners had contracted COVID-19 in the last 200 days. Lo and behold, they found the virus in 17.4% of cases. Of the animals, 4.2% also showed symptoms.

About a quarter of the animals that had been infected were also sick. Although the course of the illness was mild in most of the animals, three were considered to be severe. Nevertheless, medical experts are not very concerned. They say pets do not play an important role in the pandemic. The biggest risk is human-to-human transmission.

The fact that cats can become infected with coronaviruses has been known since March 2020. At that time, the Veterinary Research Institute in Harbin, China, had shown for the first time that the novel coronavirus can replicate in cats. The house tigers can also pass on the virus to other felines, but not very easily, said veterinarian Hualan Chen at the time.

But cat owners shouldn't panic. Felines quickly form antibodies to the virus, so they aren't contagious for very long. Anyone who is acutely ill with COVID-19 should temporarily restrict outdoor access for domestic cats. Healthy people should wash their hands thoroughly after petting strange animals.

Should this pet pig keep a safe distance from the dog when walking in Rome? That question may now also have to be reassessed. Pigs hardly come into question as carriers of the coronavirus, the Harbin veterinarians argued in 2020. But at that time they had also cleared dogs of suspicion. Does that still apply?

Nadia, a four-year-old Malaysian tiger, was one of the first big cats to be detected with the virus in 2020 — at a New York zoo. "It is, to our knowledge, the first time a wild animal has contracted COVID-19 from a human," the zoo's chief veterinarian told National Geographic magazine.

In early December 2021, two hippos at Antwerp Zoo in Belgium tested positive for coronavirus. Both animals, mother Hermien and daughter Imani, had a cold. Otherwise, they were doing well. The zoo had to close temporarily and quarantine the hippos.

It is thought that the virus originated in the wild. So far, bats are considered the most likely first carriers of SARS-CoV-2. However, veterinarians assume there must have been another species as an intermediate host between them and humans in Wuhan, China, in December 2019. Only which species this could be is unclear.

This racoon dog is a known carrier of the SARS viruses. German virologist Christian Drosten spoke about the species being a potential virus carrier. "Racoon dogs are trapped on a large scale in China or bred on farms for their fur," he said. For Drosten, the racoon dog is clearly the prime suspect.

Pangolins are also under suspicion for transmitting the virus. Researchers from Hong Kong, China and Australia have detected a virus in a Malaysian Pangolin that shows stunning similarities to SARS-CoV-2.

Hualan Chen also experimented with ferrets. The result: SARS-CoV-2 can multiply in the scratchy martens in the same way as in cats. Transmission between animals occurs as droplet infections. At the end of 2020, tens of thousands of martens had to be killed in various fur farms worldwide because the animals had become infected with SARS-CoV-2.

Experts have given the all-clear for people who handle poultry, such as this trader in Wuhan, China, where scientists believe the first case of the virus emerged in 2019. Humans have nothing to worry about, as chickens are practically immune to the SARS-CoV-2 virus, as are ducks and other bird species.

So far, 18.7 million people have received COVID-19 vaccine boosters in Germany. Will this help against the new coronavirus variant omicron? Will regular boosters be needed for full immunization? DW explores what we know.  

Rights in Germany, Sweden and New Zealand held up well during COVID, a new study has found. Meanwhile, India has no plans to offer booster shots just yet. Follow DW for the latest.  

Researchers in South Africa say there appears to be evidence that the omicron strain of coronavirus is less virulent than delta. In the US, New York state is to reintroduce its mask mandate. Follow DW for more.  

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