People report Li Wenliang, 34, had been detained by police in late December for “rumor-mongering” after he spoke publicly about the threat of coronavirus

Li returned to his job at Wuhan Central Hospital, where patients continued to come in with the mysterious respiratory illness. The Chinese government kept the new coronavirus under wraps until Jan. 7, while telling citizens not to believe online rumors about a virus. The new coronavirus has now spread to 28,275 people worldwide, including 12 in the U.S., and 563 people in China have died.

On Jan. 10, Li said he started coughing and checked himself into his hospital the next day. He was diagnosed with coronavirus three weeks later, on Feb. 1. Li spent his final days in the hospital’s intensive care unit, and tried to stay upbeat, posting on social media that he intended to get better and return to his job.

“I’ve seen the support and encouragement so many people online have given me,” he wrote on Weibo, the Chinese messaging app. “It makes my feel a little more relaxed in my heart.”

Li said that his parents are both hospitalized with fever, and that he lives with his pregnant wife and young child, though he did not say if any of them have tested positive for coronavirus.

Dr. Mike Ryan, executive director of the World Health Organization, shared his condolences on WHO’s Twitter account on Thursday.

We are deeply saddened by the passing of Dr Li Wenliang. We all need to celebrate work that he did on #2019nCoV – @DrMikeRyan