As word of a mysterious virus mounted, Li Wenliang shared suspicions in a private chat with his fellow medical school graduates.

The doctor said that seven people seemed to have contracted SARS — the respiratory illness that spread from China to more than two dozen countries and left hundreds dead in the early 2000s. One patient was quarantined at his hospital in Wuhan, China, Li said. He urged people to be careful.

Li and seven other doctors were quickly summoned by Chinese authorities for propagating “rumors” about SARS-like cases in the area — but their warnings were prescient. Soon, health officials worldwide would be scrambling to combat a novel virus with a striking genetic resemblance to SARS. The outbreak in Wuhan has exploded to more than 20,000 confirmed cases just in China.

Among the ill: the ophthalmologist who was censured for sounding an early alarm.

“The diagnosis is finally confirmed,” Li posted Jan. 31 on the social media platform Weibo.

Li’s situation has drawn rare acknowledgment of official missteps in China, where a bureaucratic culture that prioritizes political stability over all else probably allowed the new coronavirus to spread farther and faster. Late last month, China’s highest court admonished the Wuhan police for the detentions.

“If society had at the time believed those ‘rumors,’ and wore masks, used disinfectant and avoided going to the wildlife market as if there were a SARS outbreak, perhaps it would’ve meant we could better control the coronavirus today,” the court said. “Rumors end when there is openness.”

Li, an ophthalmologist at Wuhan Central Hospital, had shared his concerns the same day that Chinese authorities confirmed they were investigating 27 cases of viral pneumonia. Officials at the epicenter in Wuhan — the capital of Hubei province, where millions are now trapped in an unprecedented lockdown — sent an “urgent notice” to all hospitals about the existence of “pneumonia of unclear cause."

The notice ordered all departments to immediately compile information about known cases and report them up their chain of command. But it did not mention SARS or a coronavirus.

Li had posted a snippet of an RNA analysis finding “SARS coronavirus” and extensive bacteria colonies in a patient’s airways, according to a chat transcript that he and other chat members later shared online.

On Jan. 1, the Wuhan Public Security Bureau issued summons to Li and the others accused of fanning rumors. The detentions were reported on “Xinwen Lianbo,” a newscast watched by tens of millions.

The police followed up in the state-run Xinhua News Agency with a chilling warning.

“The police call on all netizens to not fabricate rumors, not spread rumors, not believe rumors,” the Wuhan authorities said, adding that they encouraged Web users to “jointly build a harmonious, clear and bright cyberspace.”

As authorities cracked down, the outbreak was quickly worsening amid an information vacuum. Wang Guangbao, a surgeon and popular science writer in eastern China, later said that speculation about a SARS-like virus was rampant around Jan. 1 within medical circles, but that the detentions dissuaded many, including himself, from speaking openly about it.

“The eight posters getting seized made all of us doctors feel we were at risk,” he said.

Wuhan police released Li on Jan. 3 after he signed a document saying that he committed “illegal acts.” The doctor, who did not immediately respond to The Washington Post on Tuesday, later explained to CNN that his family would “worry sick” about him “if I lose my freedom for a few days.” CNN reported that he was able to leave the police station within about an hour.

He hurried back to work to see sick patients — and worked “normally” for a while, he wrote on Weibo, tending to patients with the new coronavirus.

Then, on Jan. 10, he got a cough.

The next day, Li wrote, he had a fever, and by Jan. 12 he was in the hospital. Tests for the virus he had been scrutinizing came back negative, but he was having a hard time breathing and moving.

China had yet to declare an emergency. That would come on Jan. 20, as more than 400 million Chinese people prepared to travel home to mark the Lunar New Year. A renowned pulmonologist appeared on state media to announce that the new virus was transmissible between people, and Chinese leader Xi Jinping called for quick information-sharing and “resolute efforts” to contain the virus.

Within days, all of Wuhan and several nearby cities — an area the size of Washington state with more than 50 million people — were locked down. Authorities raced to accommodate ballooning numbers of patients, working to erect entire new hospitals.

By late January, officials were also acknowledging mistakes.

The Supreme People’s Court rebuked police for punishing Li and his fellow doctors. Wuhan police said in a statement a day later that the eight people summoned had committed only mild transgressions, spreading “unverified information.”

Officials gave “education and criticism” and did not fine or detain people, the police said.

Li, who emphasized that his license has not been revoked, said he has been cheered in the hospital by “netizens’ support and encouragement.” His last post on Weibo, the Feb. 1 announcement of his latest test results, drew tens of thousands of comments.

“Dr. Li, you are a good doctor with conscience,” read one well-wisher’s message with more than 100,000 upvotes.

Another person counted Li among eight “prophets.”

“The people of the whole country are in solidarity with you,” the commenter said.

Lena H. Sun and Emily Rauhala contributed to this report.