New York,  A team of researchers from Boston University claim to have created, after a series of tests, a new Covid-19 strain with an 80 per cent kill rate, from the one initially believed to have launched the worldwide pandemic that started in China.

According to Fox News, the variant, a combination of Omicron and the original virus in Wuhan, killed 80 per cent of the mice infected with it, the university said.

When mice were only exposed to Omicron, they experienced mild symptoms, the report said.

The team, from Florida and Boston at the school's National Emerging Infectious Diseases Laboratories, extracted the spike protein from Omicron and attached it with the strain first detected at the onset of the pandemic that began in China's Wuhan.

They then documented how the mice reacted to the hybrid strain.

"In mice, while Omicron causes mild, non-fatal infection, the Omicron S-carrying virus inflicts severe disease with a mortality rate of 80 per cent," they were quoted as saying in a research paper.

The new strain has five times more infectious virus particles than the Omicron variant, the researchers said.

In a statement, the university stressed that the replicated strain was less dangerous than the original strain.