Among the Omicron strains of the new coronavirus, ``BA.5'', which has become mainstream since the ``7th wave'' of this summer, has a degree of symptoms when infected with ``BA.2'' since the beginning of this year. A group from the University of Tokyo and others announced the results of experiments with animals that were equivalent and relatively low.
This research was conducted by a group led by Project Professor Yoshihiro Kawaoka of the Institute of Medical Science, the University of Tokyo, and was published in the scientific journal Nature.
In the research, hamsters were infected with Omicron strains such as BA.5 and BA.2, which were taken from people who were actually infected, and the differences in symptoms were investigated.
Comparing the changes in body weight, which is an indicator of the physical condition of hamsters, it decreased when infected with the delta strain that spread last summer, whereas it decreased in either BA.5 or BA.2. Even in that case, they weighed about the same as if they hadn't been infected with the virus.
In addition, when infected with either "BA.5" or "BA.2", the respiratory symptoms that appeared in the delta strain were not observed, and examination of lung tissue showed no inflammation, and no infection. The pathogenicity of was relatively low.
Professor Kawaoka said, "Even in humans, the pathogenicity of the two viruses, 'BA.5' and 'BA.2', is thought to be almost the same. I would like to clarify the cause of this," he said.