House of Representatives member Jiro Hatoyama's office said Monday one of the lawmaker's secretaries has contracted the new coronavirus, becoming the first among those working at a Tokyo office building for Japanese parliament members to become infected.

The secretary, in his 60s, developed a fever on the night of April 5, and it was confirmed Saturday that he was positive for COVID-19, the disease caused by the virus. The lower house secretariat has disinfected Hatoyama's office upon being notified of the case on Monday.

The aide of Hatoyama, son of the late veteran lawmaker Kunio Hatoyama and a scion of a prominent political family, has only shown mild symptoms but will be hospitalized.

The secretary had been working from home since last week had not been in close contact with the 41-year-old lawmaker elected from Fukuoka Prefecture, according to the office.

The lower house secretariat said when a lawmaker or a secretary tests positive for the virus or is deemed to have been in close contact with those infected, it will try to track their activities and interactions for the previous two weeks and disinfect the office and parliament buildings if necessary.

Hatoyama has been elected twice and belongs to the ruling Liberal Democratic Party. His father, who died in 2016, held several ministerial posts.

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