Researchers at the Boston University (BU) in USA have created a hybrid Covid variant - combining Omicron and the original Wuhan strain - that killed 80 per cent of mice in a study.

The research has sparked outrage on social media as it shows that dangerous virus manipulation research continues to go on even in the US, despite fears similar practices may have started the Covid-19 pandemic.

The scientists at BU’s National Emerging Infectious Diseases Laboratories found that all mice infected with only the BA.1 omicron variant had mild cases and survived, while the combined omicron spike protein with original COVID-19 virus strain inflicted severe disease with an 80 per cent mortality rate.

In the study, which has not been peer-reviewed, the researchers extracted Omicron's spike protein - the unique structure that binds to and invades human cells.

It has always been present in the virus but has become more evolved over time. Omicron has dozens of mutations on its spike protein that made it so infectious.

Researchers attached Omicron's spike protein to the original wildtype strain that first emerged in Wuhan at the start of the pandemic.

The researchers looked at how mice fared against the new Covid strain compared to the original Omicron variant.

When a similar group of rodents were exposed to the standard Omicron strain, however, they all survived and only experienced 'mild' symptoms. 

Meanwhile, scientists and netizens have condemned the research.

Professor Shmuel Shapira, a leading scientist in the Israeli Government, said, "This should be totally forbidden, it's playing with fire".

Dr Richard Ebright, a chemist at Rutgers University in New Brunswick, was quoted in a DailyMail.com report as saying that the research is a "a clear example of gain of function research".

In a gain of function research, viruses are purposefully manipulated to be more infectious or deadly.

'If we are to avoid a next lab-generated pandemic, it is imperative that oversight of enhanced potential pandemic pathogen research be strengthened," he added.

However, the Boston University has disputed the claims that the research had created a more dangerous virus.

“First, this research is not gain-of-function research, meaning it did not amplify the Washington state SARS-COV-2 virus strain (original virus from 2020) or make it more dangerous,” BU said in a statement following the outrage.

“In fact, this research made the virus replicate less dangerous,” the university added.

The testing actually showed, though, that the chimeric virus was more lethal to a type of lab mice than Omicron itself, killing 80 per cent of the mice infected.

Importantly, the original Wuhan strain killed 100 per cent of mice it was tested in, the university said.

This study provides important insights into omicron’s ability to cause disease, according to the researchers.

There is no evidence the work, performed under biosecurity level 3 precautions in BU’s National Emerging Infectious Diseases Laboratories, was conducted improperly or unsafely.

In fact, it was approved by an internal biosafety review committee and Boston’s Public Health Commission, the university said Monday (18 October) night.

However, the research team did not clear the work with the US National Institute of Allergy and Infectious Diseases, which was one of the funders of the project.

The agency indicated it is going to be looking for some answers as to why it first learned of the work through media reports.

The BU team’s original grant applications did not specify that the scientists wanted to do this precise work, said Emily Erbelding, director of NIAID’s division of microbiology and infectious diseases, reports Stat News.

The research group also did not make clear that it was doing experiments that might involve enhancing a pathogen of pandemic potential in the progress reports it provided to NIAID, the report added.