“Here we demonstrated that the Omicron BA.4/5 are more potentially pathogenic than Omicron BA.2. Therefore, our observations strongly suggest that SARS-CoV-2 does not necessarily evolve to attenuate its pathogenicity.”.
“Three histological parameters, including bronchitis/bronchiolitis, hemorrhage/congestion and alveolar damage, as well as the total score of histology of rBA.2.12-infected hamsters were significantly higher than those of rBA.2-infected hamsters. More importantly, all histopathological parameters were highest in rBA.4/5-infected hamsters with statistical significances.”
“Furthermore, in the lungs of infected hamsters at 5 d.p.i., the level of inflammation with type II alveolar pneumocyte hyperplasia by rBA.4/5 infection was significantly higher than that by rBA.2 infection, while there was no statistically significant difference between rBA.2.12.1 and rBA.2 infections. The relatively more severe disorders in the lungs of rBA.4/5-infected hamsters than those of rBA.2-infected hamsters were supported by the more efficient spread of rBA.4/5 than rBA.2 in the infected lungs.”