A controversial research paper claims the new coronavirus has split into two distinct strains and that it is possible to be infected with both, but some experts are unconvinced.

A joint study by researchers from multiple Chinese universities, which has been accepted by Chinese journal National Science Review, looked at 103 genomes of SARS-CoV-2 and found the virus had evolved into two separate strains, known as "S" and "L", with the "L" type being newer, more prevalent and more aggressive.

Viruses are known for constantly mutating — in fact, these mutations are so rapid that scientists can use them to trace where in the world patients might have picked up the virus — but the authors of this study say the two types are so distinct they can be described as two strains.

In contrast, other experts in the field say the two types the Chinese researchers claimed to have identified were a result of both normal viral mutation and errors in data that they were relying on.

University of Queensland virologist Ian Mackay said there were fundamental problems with the study, including that some of the data, which was published on a database shared by researchers, had not yet been "cleaned up".

"[The differences] are sequence errors which in fact were corrected [by the submitting scientist] very soon after they were originally uploaded to the GISAID database," Professor Mackay said.

He said the patterns they identified were no more than normal variation.

"They're almost all identical. It's like us putting on different clothes from day to day," Professor Mackay said.

"I can't believe this has been peer reviewed. It's a weak paper and poor science."

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The paper also suggested a patient from Queensland "might have been infected by at least two different strains" but Professor Mackay dismissed this claim, saying it did not fit with the evidence provided.

Because the coronavirus was so new, the amount of data available on it was still small, wrote Oscar Maclean from the University of Glasgow on virology discussion forum Virological.

"Two of the key claims made by this paper appear to have been reached by misunderstanding and over-interpretation of the SARS-CoV-2 data, with an additional analysis suffering from methodological limitations," Dr Maclean wrote.

On Twitter, Swiss biologist Richard Neher wrote of the paper that "just taking values at face values will result in wrong, misleading, or downright dangerous inferences".

The study also looked at the evolution of SARS-CoV-2 and other related coronaviruses in an attempt to figure out which animal the virus evolved through before it got to humans.

It is well accepted that the virus originated in bats, but some studies had suggested it came to humans via pangolins. This new study casts doubt on that, although Professor Mackay said it was not the first to do so.

Editor's note 6/3/20: An earlier version of this story gave more emphasis to the claims made in the National Science Review paper. It has since been updated.