The Wuhan Central Hospital said on its social media account that Dr. Li Wenliang, a 34-year-old ophthalmologist, was "unfortunately infected during the fight against the pneumonia epidemic of the new coronavirus infection."
"We deeply regret and mourn this," it added.
Li was reprimanded by local police for "spreading rumors" about the illness in late December, according to news reports. The outbreak, centered in Wuhan, has now infected over 28,200 people globally and killed more than 560, triggering travel restrictions and quarantines around the world and a crisis inside the country of 1.4 billion.
The World Health Organization tweeted: "We are deeply saddened by the passing of Dr Li Wenliang. We all need to celebrate work that he did" on the virus.
Within a half-hour of announcing earlier Friday that Li was in critical condition, the hospital received nearly 500,000 comments on its social media post, many of them from people hoping Li would pull through. One wrote: "We are not going to bed. We are here waiting for a miracle."
Li was among a number of medical professionals in Wuhan who tried to warn colleagues and others when the government did not, The New York Times reported earlier this week. It said that after the mystery illness had stricken seven patients at a hospital, Li said of them in an online chat group Dec. 30: "Quarantined in the emergency department."
Another participant in the chat responded by wondering, "Is SARS coming again?" — a reference to the 2002-03 viral outbreak that killed hundreds, the newspaper said.
Wuhan health officials summoned Li in the middle of the night to explain why he shared the information, and police later forced him to sign a statement admitting to "illegal behavior," the Times said.
"If the officials had disclosed information about the epidemic earlier," Li said in an interview in the Times via text messages, "I think it would have been a lot better. There should be more openness and transparency."
In other developments in the outbreak:
YOUNGEST PATIENT
A newborn in China became the youngest known person infected with the virus.
The baby was born Saturday in Wuhan and confirmed positive just 36 hours after birth, authorities said. But precisely how the child became infected was unclear.
"The baby was immediately separated from the mother after the birth and has been under artificial feeding. There was no close contact with the parents, yet it was diagnosed with the disease," Zeng Lingkong, director of neonatal diseases at Wuhan Children's Hospital, told Chinese TV.
Zeng said other infected mothers have given birth to babies who tested negative, so it is not yet known if the virus can be transmitted in the womb.
MORE HOSPITAL BEDS
China finished building a second new hospital Thursday to isolate and treat patients — a 1,500-bed center in Wuhan. Earlier this week, another rapidly constructed, 1,000-bed hospital in Wuhan with prefabricated wards and isolation rooms began taking patients.
Authorities also moved people with milder symptoms into makeshift hospitals at sports arenas, exhibition halls and other public spaces.
All together, more than 50 million people are under virtual quarantine in hard-hit Hubei province in an unprecedented — and unproven — bid to bring the outbreak under control.
In Hong Kong, hospital workers demanding a shutdown of the territory's border with mainland China were on strike for a fourth day. Hong Kong leader Carrie Lam announced a 14-day quarantine of all travelers entering the city from the mainland starting Saturday, but the government has refused to seal the border entirely.
QUARANTINED CRUISE SHIPS
Two docked cruise ships with thousands of passengers and crew members remained under 14-day quarantines in Hong Kong and Japan.
Ten passengers confirmed to have the virus were escorted off the Diamond Princess at the port of Yokohama near Tokyo, after 10 others were taken off the previous day. About 3,700 people were confined aboard the ship.
"It's going to be like a floating prison," passenger David Abel lamented on Facebook. He had set out on a 50th wedding anniversary luxury cruise but found himself in his cabin, eating a "lettuce sandwich with some chicken inside."
More than 3,600 people on the other quarantined ship, the World Dream, underwent screening after eight passengers were diagnosed with the virus.
NEW DRUG
Testing of a new antiviral drug was set to begin on a group of patients Thursday, the official Xinhua News Agency reported. The drug, Remdesivir, is made by U.S. biotech company Gilead Sciences.
Antivirals and other drugs can reduce the severity of an illness, but "so far, no antivirals have been proven effective" against the new virus, said Thanarak Plipat, deputy director-general of Thailand's Disease Control Department in the Health Ministry. He said there are a lot of unknowns, "but we have a lot of hope as well."
MORE FALLOUT
From Europe to Australia and the U.S., universities that host Chinese students or have study-abroad programs are scrambling to assess the risks, and some are canceling opportunities and prohibiting student travel.
Central banks in the Philippines and Thailand have cut their interest rates to fend off economic damage from the outbreak in China, the world's second-biggest economy, with 1.4 billion people. China is a major source of tourists in Asia, and corporations around the world depend on its factories to supply products and its consumers to buy them.
The organizers of the Tokyo Olympics again sought to allay fears that the 2020 Games could be postponed or canceled because of the crisis.