Questions Swirl over China's Unexplained Pneumonia Outbreak

The WHO said there is limited information to form a risk assessment. The link to the wholesale fish and animal market could signal a link to an animal source. It added that the patients’ symptoms are common to several respiratory diseases, and that pneumonia is common in the winter. “However, the occurrence of 44 cases of pneumonia requiring hospitalization clustered in space and time should be handled prudently,” the agency said.

Wuhan is the capital of Hubei province, which is home to 58 million people, the WHO said, adding that it has requested more information on lab tests performed and the differential diagnoses that clinicians considered.

The WHO said it doesn’t recommend any specific measures for travelers and urged travelers who experience respiratory symptoms during or after travel to seek medical attention and share their travel history with health providers.

CDC Issues Travel Watch
In a related development, the U.S. Centers for Disease Control and Prevention (CDC) on Monday issued a level 1 travel watch—the lowest of its three levels—for China’s outbreak. It said the cause and the transmission mode aren’t yet known, and it advised travelers to Wuhan to avoid living or dead animals, animal markets, and contact with sick people.

The CDC said the market connected to the mystery outbreak sells chickens, bats, marmots, and other wild animals and has been closed since Jan 1 for cleaning and disinfection.

“The situation is evolving. This notice will be updated as more information becomes available,” it said. The CDC also urged clinicians to take a cautious approach to sick patients who have a history of travel to Wuhan.

Regional governments flag sick travelers

As a precaution, some administrative regions and countries near China have stepped up screening in people who traveled to Wuhan, but so far, there’s no indication that any of them are part of the Wuhan cluster.

As of today, Hong Kong has identified 21 sick travelers arriving from Wuhan, and most have tested positive for different respiratory viruses, according to an enhanced surveillance list from the Centre for Health Protection (CHP). They include seasonal influenza (2009 H1N1 and H3N2), human rhinovirus, enterovirus, parainfluenza type 1, respiratory syncytial virus (RSV), coronavirus 229E, coronavirus OC43, and metapneumovirus.

In a separate statement Monday, the CHP said that over the past 24 hours six patients who had been to Wuhan in the past 14 days presented for medical care. None had visited live-animal markets in Wuhan before their symptom onsets, and all are in stable condition. Of 21 sick travelers identified so far, 7 have been discharged.

According to media reports over the weekend, Singapore identified a sick Wuhan traveler, a child who tested positive for RSV, and Taiwan identified eight passengers with mild symptoms, with tests results for four of them revealing common viruses such as seasonal flu.

No Sign of a Rapidly Escalating Situation
Michael T. Osterholm, PhD, MPH, said it would be useful to know more details about testing, including more details on results that were negative. For now, the key message is that the outbreak isn’t rapidly escalating, he added.

Osterholm is director of the University of Minnesota’s Center for Infectious Disease Research and Policy, which publishes CIDRAP News.

Experts in and outside of China have raised the possibility that a new type of coronavirus may be responsible, and since the SARS outbreak in 2003, scientists have been looking for clues about how that virus emerged and for warning signs of any newly emerging similar viruses.

Earlier Coronavirus Investigations
In April 2018, Chinese researchers and their collaborators in the United States identified a novel coronavirus that triggered die-offs in piglets at four farms in Guangdong province in 2016 and 2017. The new coronavirus, called swine acute diarrhea syndrome coronavirus (SADS-CoV) in the piglets matched genetic sequences found in Chinese horseshoe bats, which are known to harbor SARS-like viruses.

Blood tests on farm workers were negative for exposure to SADS-CoV (see “New SARS-like Virus from Bats Implicated in China Pig Die-Off,” CIDRAP, 5 April 2018).

In a 2017 study, Chinese researchers who spent 5 years analyzing SARS-related viruses in horseshoe bats in a cave in Yunnan province found 11 that had all the genetic building blocks of the strain that infected humans, including 3 that use the same receptor to enter human cells (see “Bat Cave Study Finds New Clues about SARS Virus Origin,” CIDRAP, 1 December 2017).

Osterholm said if the pathogen implicated in the Wuhan cluster is a coronavirus, he worries about possible hospital outbreaks and a “superspreader” event. “But without evidence that a coronavirus is involved, we just don’t know,” he added.