Study: Omicron may be less pathogenic than Delta

The group is led by Associate Professor Sato Kei of the University of Tokyo's Institute of Medical Science and Professor Fukuhara Takasuke of Hokkaido University's Graduate School of Medicine.

The research results have been released online.

The group's studies compared Omicron with the Delta variant and an early pandemic coronavirus.

The group says Delta and the early strain in cell cultures broke up infected cells and induced cell-cell fusions, but Omicron did not show such fusions.

The group also infected hamsters with each of the three viruses.

The researchers say those infected with Delta or the early strain showed weight loss, exacerbation of pneumonia or bleeding in the lung.

By contrast, they say hamsters infected with Omicron did not show such weight change, and their pneumonia did not become serious.

The researchers say the findings about Omicron in their study are just those in an experimental animal model. But they say the results suggest that symptoms of the variant may be milder than Delta and others.

Fukuhara warns people to remain on alert for Omicron as well because it can cause pneumonia and the number of people in serious condition may increase if it spreads.