A baby girl under a year old was rushed to hospital Wednesday after her heart stopped beating, and was then found to be infected with the novel coronavirus, according to the Yamanashi Prefectural Government.

Doctors managed to revive her but she remains in a serious condition and is undergoing treatment in intensive care at University of Yamanashi Hospital, it said.

"She is in a very bad condition. Her life is likely in danger," a hospital official said.

The hospital said it asked its 44 medical staff including doctors who attended to the baby to self-isolate for two weeks. No one suspected the baby was infected at the time she was brought in for treatment, so proper preventive measures were not taken at the time, it said.