Scientists in America created a new strain of engineered Covid with an 80% kill rate after splicing part of one of the newest Omicron mutations onto samples of some of the earliest Covid strains found in the USA at the start of the pandemic. When the new virus strain was tested on mice in a lab, eight out of 10 died.
Mice exposed to just the Omicron strain fell ill, but none died. Mice who were exposed to the original strain, from Washington State, all died. Researchers at Boston University are trying to find out whether part of the protein of the Omicron variant explains why it usually causes less severe disease.
The researchers say the new strain was actually less lethal to the mice than the original virus - the one they spliced Omicron proteins onto.
The mice used in the experiment are engineered to be sensitive to Covid, with lungs modified to be highly receptive to Covid infection. They were also exposed to a vast amount of the virus.
The experiments were conducted in a biosafety level-3 lab with a series of sealed doors, negative air pressure cabinets, and researchers in protective suits.
Boston University says the experiments didn't make the original Covid-19 strain more dangerous. In a statement, they said: "It did not amplify the Washington state SARS-COV-2 virus strain (original virus from 2020) or make it more dangerous.
"In fact, this research made the virus replicate less dangerous."
Covid normally has a fatality rate in humans of around 1%. Newer strains have been found not to cause more serious illnesses, with vaccines proving effective.
An investigation is under way to determine whether the university should have informed authorities of what it was doing before the experiment was conducted.
