A variant of the coronavirus omicron may have acquired at least one of its mutations by collecting a fragment of genetic material from another virus - probably the one that causes the common cold - present at the same time in infected cells, say US scientists.

This genetic sequence does not appear in any previous version of the coronavirus, called SARS-KOV-2, but is present in many other viruses, including those that cause colds, and also in the human genome, scientists say.

By incorporating the clip into its own structure, the omicron could look "more humane", which would help it avoid an attack by the human immune system, said Wenky Soundararayan of the Cambridge-based data analysis company.

The results of his study are published on the website OSF Preprints.

This may mean that the virus is more easily transmitted and causes only mild or asymptomatic disease.

Scientists still do not know if omicron is more contagious than other variants, if it causes more severe disease, and if it will suppress the delta as the most common variant.

These questions may take several weeks to resolve.

The mutation could occur in a person with both viruses

According to previous studies, cells in the lungs and gastrointestinal tract can simultaneously host the SARS-KOV-2 virus and the common cold virus.

Such co-infection creates the conditions for viral recombination, a process in which two different viruses in the same host cell interact with each other to copy each other, creating new copies that have the genetic material of both "parents".

The new mutation could first occur in a person infected with both pathogens when a variant of the SARS-KOV-2 virus "assembles" the genetic sequence of another virus, Soundararayan and colleagues said in a study that has not yet been fully explored.

The same genetic sequence occurs many times in one of the human cold-causing coronaviruses - known as HCoV-229E - and in the human immunodeficiency virus (HIV) that causes AIDS, Soundararayan said.

"We probably overlooked a lot of recombinations"

South Africa, where omicron was first identified, has the highest HIV rate in the world, which weakens the immune system and increases a person's susceptibility to infections with cold viruses and other pathogens.

There are many people in that part of the world who may have had a recombination that introduced that ubiquitous set of genes into the omicron, Soundararayan said.

"We have probably neglected the many recombinations that have occurred over time that have led to the emergence of omicrons," Saundararayan added.

More research is needed to confirm the origin of omicron mutations and their effect on virus function and transmission.

There are other hypotheses that the latest variant omicron may have spent some time developing in the host animal.

Meanwhile, according to Soundararayan, the new findings underscore the importance of people receiving currently available coronavirus vaccines.

"You need to be vaccinated to reduce the chances of other people who are immunocompromised getting the SARS-KOV-2 virus," Soundararayan said.