Japan on Friday reported 41 new cases of a virus on a cruise ship that's been quarantined in Yokohama harbor while the death toll in mainland China rose to 636, including a doctor who got in trouble with authorities in the communist country for sounding an early warning about the disease threat.

Following an online uproar over the government's treatment of Dr. Li Wenliang, 34, the ruling Communist Party said it was sending an investigation team to “fully investigate relevant issues raised by the public” regarding the case.

Two docked cruise ships with thousands of passengers and crew members remained under 14-day quarantines in Hong Kong and Japan.

Before Friday's 41 confirmed cases, 20 infected passengers were escorted off the Diamond Princess at Yokohama near Tokyo. About 3,700 people have been confined aboard the ship.

Japanese Prime Minister Shinzo Abe announced Thursday that Japan will deny entry of foreign passengers on another cruise ship heading to Japan — Holland America's cruise ship Westerdam, on its way to Okinawa from Hong Kong — because of suspected virus patients found on the ship.

The new immigration policy takes effect Friday to ensure border control to prevent the disease from entering and spreading further into Japan, Abe said.

Meanwhile, a newborn discovered infected 36 hours after birth has become the youngest known patient. The number of people infected globally has risen to more than 31,000.

Dr. Li had worked at a hospital in the epicenter of the outbreak in the central city of Wuhan. He was one of eight medical professionals in Wuhan who tried to warn colleagues and others when the government did not, writing on his Twitter-like Weibo account that on Dec. 3 he saw a test sample that indicated the presence of a coronavirus similar to SARS, which killed nearly 800 people in a 2002-2003 outbreak that the government initially tried to cover-up.

Li wrote that after he reported seven patients had contracted the virus, he was visited on Jan. 3 by police, who forced him to sign a statement admitting to having spread falsehoods and warning him of punishment if he continued.

A copy of the statement signed by Li and posted online accused him of making “false statements” and “seriously disturbing social order.”

“This is a type of illegal behavior!” the statement said.

Li wrote that he developed a cough on Jan. 10, fever on Jan. 11 and was hospitalized on Jan. 12, after which he began having trouble breathing.

He also wrote that he had not in fact had his medical license revoked, a reference to the sort of extrajudicial retaliation the communist authorities meet out to rights lawyers and others seen as troublemakers.

“Please rest easy, I will most certainly actively cooperate with the treatment and seek to obtain an early discharge!” Li wrote on Jan. 31. He posted again on Feb. 1, saying he had been confirmed as having the virus.

On Friday, the Global Times, a Communist Party newspaper and usual staunch defender of the authorities, reported that “many said the experience of the eight ‘whistleblowers’ was evidence of local authorities' incompetence to tackle a contagious and deadly virus."

It quoted Zeng Guang, chief epidemiologist at the Chinese Center for Disease Control and Prevention, as telling the paper’s editor that “we should highly praise the eight Wuhan residents.”

"They were wise before the outbreak," Zeng was quoted as saying. The paper also cited online voices saying local authorities owe Li an apology. It quoted one posting as saying, "We lost a hero." “If his warning could send an alarm, the outbreak might not have continued to worsen,” the posting said.

“Looking back, his professional sense of vigilance in particular is worthy of our respect,” the paper said in an editorial.

The police action against the eight whistleblowers also garnered a rare and extremely subtle rebuke from the nation’s highest court. “We have the responsibility to express to society our legal thoughts about solving the problem of rumors,” a posting on the court’s Weibo account said.

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.”

The baby born last Saturday in Wuhan and confirmed positive just 36 hours after birth became the youngest known person infected with the virus, 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.

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.

China's official news agency said Friday that President Xi Jinping urged the U.S. to “respond reasonably" to the virus outbreak in a phone call with President Donald Trump.

Beijing has complained that the U.S. was flying its citizens out of Wuhan but not providing any assistance to China.

The White House said Trump “expressed confidence in China’s strength and resilience in confronting the challenge" of the outbreak.

In Hong Kong, hospital workers demanding a shutdown of the territory's border with mainland China were still on strike. The territory's 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. Taiwan has said it will refuse entry to all non-citizens or residents who have recently visited Hong Kong, Macao or China beginning Friday.

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.