The coronavirus subvariant surging in China may be evolving to attack the brain, feel researchers, according to a media report.

The study challenges previous assumptions that viruses usually evolve to become less dangerous, South China Morning Post reported.

New research on the Omicron subvariant of the coronavirus has suggested the pathogen could be changing how it attacks the human body - shifting from infecting respiratory systems to increasingly targeting the brain.

Researchers from Australia and France found BA.5 - the coronavirus subvariant driving what is now the world's biggest surge of infections in China - did much more severe damage to mouse brains and cultured human brain tissues than the previous BA.1 subvariant, leading to brain inflammation, weight loss and death, South China Morning Post reported.

"Compared with BA. 1, we found that a BA.5 isolate displayed increased pathogenicity in K18-hACE2 in experimental models with rapid weight loss, brain infection and encephalitis, and mortality. In addition, BA.5 productively infected human brain organoids significantly better than BA. 1," a manuscript of the research said.

The manuscript has been uploaded to the preprint platform bioRxiv, and will receive peer review for publication.

"These results suggest that the Omicron lineage is not evolving towards reduced pathogenicity," wrote the team, which was led by virologist Andreas Suhrbier from the QIMR Berghofer Medical Research Institute in Queensland, Australia, South China Morning Post reported.

However, other experts have sounded a note of caution, noting that a major limitation of the study was the experimental model it used, which they said probably did not apply to human beings.

"They showed that all the experimental subjects died from brain infections of BA. 5, which is apparently very different from human infections that we know of," said Jin Dongyan, a virologist at the University of Hong Kong, the report said.

Jin said it was widely accepted that BA.5 did not cause more brain abnormalities in humans than previous subvariants, adding that the World Health Organisation has said the pathogenicity of Omicron variants has not increased.

In a paper published in the journal Nature last month, a team of Japanese and US scientists reported that BA.5 seemed to have inherited the reduced pathogenicity of Omicron subvariants, SCMP reported.

Multiple studies have shown that BA.5 is more transmissible than other Omicron subvariants and can evade a human immune system with a previous COVID-19 vaccination or infection. The strain has been detected in more than 100 nations and was the dominant strain in countries such as the United States and the United Kingdom a few months ago.