Tests confirmed Friday that a bleeding ulcer was the cause of New Hampshire Gov. Chris Sununu‘s flulike symptoms, his chief of staff said.

Sununu was admitted to a hospital earlier in the day after having flulike symptoms since Wednesday. He had tested negative three times for COVID-19.

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“Tests have confirmed that a bleeding ulcer caused the symptoms the Governor has been experiencing this week,” Chief of Staff Jayne Millerick said in a statement. “After blood transfusion today, he is doing much better. He is extremely grateful to the staff at Portsmouth Hospital for their outstanding care and to everyone who donates blood. As a blood donor himself, he is happy he paid it forward and grateful to all who do the same.”

It was not immediately known how long Sununu would remain hospitalized.

Sununu, a Republican, had said Wednesday he tested negative for COVID-19, hours after his office said he wasn’t feeling well, postponed a meeting and began isolating.

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“I woke up with symptoms similar to COVID and out of an abundance of caution I took two rapid antigen tests, which came back negative, and then followed up with a PCR test, which confirmed the negative,” Sununu had said. “I am going to rest up, and look forward to getting back to the State House soon!”

Sununu, 46, is fully vaccinated against COVID-19. He received the single-shot Johnson & Johnson vaccine on April 10.

He took a trip to Kentucky on Monday to see how officials there are handling a surge in COVID cases.

State Senate President Chuck Morse, a Republican, said he hopes Sununu has a quick recovery.

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“The entire Senate sends its best wishes to him, and I know people all across New Hampshire are keeping him in their prayers,” he said in a statement.