American researchers have developed a new lethal Covid strain in a laboratory, a hybrid of Omicron and the original Wuhan virus, which killed 80 per cent of infected mice. The study, conducted at Boston University's National Emerging Infectious Diseases Laboratories, found that the mutant variant caused severe disease in mice, while standard Omicron only led to mild symptoms and no deaths.
The scientists extracted Omicron's spike protein and attached it to the original wildtype strain from Wuhan. In human lung cells grown in the lab, the hybrid produced five times more viral particles than Omicron, suggesting it may be more infectious. However, the researchers caution that the hybrid would be unlikely to be as deadly in humans due to differences in immune responses between species.
One limitation noted was the specific breed of mice used, which are designed for severe Covid infection but do not fully replicate human responses. The Boston lab is one of 13 biosafety level 4 facilities in the US authorised to handle the most dangerous pathogens.
