A group of international researchers says that studies it conducted show the Omicron variant of the coronavirus causes less severe symptoms in the lungs of hamsters than the Delta variant.

Kawaoka Yoshihiro is one of the leaders of the group. He is a project professor at the University of Tokyo's Institute of Medical Science. The findings were released in the science journal Nature.

The researchers examined differences in symptoms in hamsters separately infected with the Omicron and the Delta variants.

They say that, three days after becoming infected, the hamsters with the Omicron variant had much smaller amounts of the virus in their lungs than those with the Delta variant.

They also say CT images show that there were cases in which animals with the Delta variant developed pneumonia, like some human COVID patients.

But they found that those with the Omicron variant had only mild inflammation in the lungs.

The researchers say that some of the hamsters with the Omicron variant died under certain circumstances.

The group says its studies with the hamsters show that the Omicron variant is less pathogenic and has a lower ability to proliferate than the Delta variant.

Even though the symptoms are milder, the researchers are still urging people to be vigilant, especially elderly people and those with weak immune systems.