Chinese researchers just confirmed that patients can transmit the coronavirus without showing symptoms. A woman passed it to 5 relatives. A 20-year-old woman from Wuhan, China, transmitted the coronavirus to her family members without ever showing any symptoms, a new study found. The woman tested positive for the virus, but her CT scans were clear and she never became physically ill. Five of her family members, however, came down with a fever. Two developed severe pneumonia. The case is evidence that the coronavirus can be transmitted when someone is asymptomatic.

Chinese researchers have confirmed a case of asymptomatic transmission of the new coronavirus: A 20-year-old woman from Wuhan passed it to five of her family members but never got physically sick herself. The case study is the first concrete evidence that a person showing no symptoms can pass the coronavirus to others — a fact that could make curbing the outbreak even more challenging. [1, 2, 3]

The researchers behind the finding said the 20-year-old woman was isolated and closely observed at the Fifth People's Hospital of Anyang. She never become physically ill, even after her family members developed fevers. Two of them got severe pneumonia. A woman dons a makeshift protective face shield at a residential compound in Wuhan, the epicenter of the novel coronavirus outbreak. [4, 5, 6, 7].

For now, the woman's asymptomatic transmission appears to be an anomaly, but health experts have documented other instances in which people tested positive for the virus without showing symptoms. [8, 9, 10] A report from the Chinese Center for Disease Control and Prevention analyzed records of all of China's reported cases of the virus from December 8 to February 11 and found that 1.2% of patients confirmed to be infected showed no symptoms. A far higher portion of asymptomatic cases was found on the Diamond Princess cruise ship, where 322 of 621 people tested positive but showed no symptoms. [1, 2, 3]

"It's very clear that the people who are getting caught in that umbrella of reporting are the people that present themselves to a hospital," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said at a briefing on February 6. "There's another whole cohort that is either asymptomatic or minimally symptomatic."

The Chinese woman tested positive for the virus, but never got sick
The 20-year-old woman in the new case study lives in Wuhan — the city where the outbreak started — but traveled to Anyang on January 10. Three days later, she went with five family members to visit a sick patient (who did not have the coronavirus) at the Anyang District Hospital. 

On January 17, one of the woman's family members came down with a fever and sore throat. The following week, the other four relatives developed a fever and respiratory symptoms. Those relatives were admitted to the Fifth People's Hospital on January 26. 

All of the family members tested positive for the coronavirus. The only person they'd had contact with who had been in Wuhan was their 20-year-old relative. When doctors initially tested the young woman for the coronavirus, the results came back negative. Her CT scan was normal, too. But a day later, she tested positive for the virus even though she wasn't showing any symptoms. By February 11, the woman still had no fever, cough, sore throat, or gastrointestinal issues. 

Doctors concluded that the woman's incubation period — the time during which she was infectious — was 19 days. Chinese health officials previously estimated that the incubation period for the virus ranged from one to 14 days, but recent research suggests it could be as long as 24 days. The US and many other countries have established quarantine rules for travelers from Wuhan based on that 14-day window. [11, 12].

Asymptomatic transmission in Germany?
Most of the coronavirus cases so far have been mild, but the virus has killed more than 2,200 people and infected more than 76,000. Though the majority of cases are on the Chinese mainland, the virus has spread to 29 other countries. [13, 14].

A case of asymptomatic transmission similar to the one described in the new case study was previously identified in Germany. But that research turned out to be flawed. According to a letter published in the New England Journal of Medicine, a woman from Shanghai transmitted the virus to a 33-year-old German businessman in January. Three days later, he felt better and went back to work, then infected at least two of his colleagues. But the researchers had not spoken with the woman, who had in fact experienced mild symptoms at the time of transmission. That left scientists unsure as to whether people who never experience any symptoms can transmit the disease — until today. [15, 16].

WHO warns overseas virus spread may be 'tip of the iceberg'

The head of the World Health Organization Tedros Adhanom Ghebreyesus has warned that confirmed cases of coronavirus being transmitted by people who have never travelled to China could be the "tip of the iceberg".

Tedros Adhanom Ghebreyesus' remarks come as members of a WHO-led "international expert mission" flew to China on Monday to help coordinate a response to the outbreak that has so far infected more than 40,000 people and killed 908 in the country.

"There've been some concerning instances of onward #2019nCoV spread from people with no travel history to (China)," Ghebreyesus tweeted Sunday, using the virus's provisional scientific name. "The detection of a small number of cases may indicate more widespread transmission in other countries; in short, we may only be seeing the tip of the iceberg."

While the virus' spread outside China appeared to be slow, Ghebreyesus warned it could accelerate. "Containment remains our objective, but all countries must use the window of opportunity created by the containment strategy to prepare for the virus's possible arrival," he said.

Outside mainland China, there have been more than 350 infections reported in nearly 30 places. There have been two deaths, one in the Philippines and the other in Hong Kong.

Several countries have banned arrivals from China while major airlines have suspended flights, and Air China cancelled some of its flights to the United States.

The WHO-led mission to China is being headed up by Bruce Aylward, a veteran of previous health emergencies, Ghebreyesus said. Aylward oversaw the WHO's 2014-2016 response to the Ebola epidemic in West Africa.

WHO said in recent days there had been "some stabilising" in the numbers of new cases of the coronavirus in China. But the UN agency cautioned it was too early to say if the virus had peaked.

The SARS-like virus is believed to have emerged late last year in the central city of Wuhan, the capital of Hubei province where millions of people are under lockdown in a bid to stop it spreading.

Republican senator suggests 'worse than Chernobyl' coronavirus could've come from Chinese 'superlaboratory'

• Republican Sen. Tom Cotton suggested that Chinese officials misled the public on the origins of the novel coronavirus from Wuhan, China, saying it may have originated in a "superlaboratory."
• At a Senate hearing with US military leaders on Thursday, Cotton said the coronavirus was "worse than Chernobyl."
• Cotton qualified his remarks by saying "we still don't know where" the virus originated, but his comments come amid numerous conspiracy theories on its origins — including one alleging the virus "originated in lab linked to China's biowarfare program."

Republican Sen. Tom Cotton suggested that Chinese officials misled the public on the origins of the novel coronavirus that has killed at least 362 people and infected more than 17,400 others, saying it may have originated in a "superlaboratory."

At a Senate Armed Service Committee hearing with US military leaders, Cotton described the coronavirus as the "biggest and most important story in the world" and "worse than Chernobyl."

Cotton, a longtime China hawk, suggested Beijing had not been as forthcoming about the number of infections and was "lying about it from the very beginning" to downplay the seriousness of the epidemic. Chinese officials have been accused of lowering the number of cases and tamping down on reports weeks before it was formally acknowledged by the government. [4, 5, 6, 7].

"They also claimed, for almost two months until earlier this week, that it originated in a seafood market in Wuhan," Cotton said, referring to a study published by The Lancet. "That is not the case." As China institutes the largest quarantine in human history, locking down more than 50 million people in the center of the country, those who have recently been to Wuhan are being tracked, monitored, turned away from hotels and shoved into isolation at their homes and in makeshift quarantine facilities.

Initial studies linked the virus to various sources, including a seafood market in Wuhan, China, and bats. In one of the studies from the Wuhan Institute of Virology, six of the seven virus samples were from patients who worked at the Huanan wholesale seafood market.

"Of the original 40 cases, 14 of them had no contact with the seafood market, including patient zero," Cotton said. "I would note that Wuhan also has China's only bio-safety level four 'superlaboratory' that works with the world's most deadly pathogens to include, yes, coronavirus."

Cotton was referring to China's first Biosafety Level 4 lab, the Wuhan National Biosafety Laboratory of the Chinese Academy of Sciences, which investigates "the most dangerous pathogens," according to the US Centers for Disease Control and Prevention.

While Cotton qualified his remarks by saying "we still don't know where" the virus originated, his comments come amid numerous conspiracy theories about the virus's origins — including one that says the virus "originated in lab linked to China's biowarfare program."

The amount of false information spreading across social-media platforms has prompted several companies, including Facebook, to limit the reach of such posts. In a statement, Facebook said it would display "accurate information" and notify users if they are suspected of sharing false or misleading information.

China accused the US of "fear and overreaction" after President Donald Trump imposed a temporary travel ban on people who had visited China within the past 14 days. "In the face of the public-health crisis, countries should work together to overcome the difficulties and not shift one's troubles onto others, let alone take advantage of people's precarious position," a Chinese foreign ministry spokeswoman said. [5]