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The mysterious and growing cluster of unexplained pneumonia cases in the Chinese city of Wuhan has infectious disease experts parsing limited public statements from Chinese authorities for clues to what is happening.

With machine-translated reports that the outbreak might be caused by a new virus, and perhaps even a new coronavirus — the family of viruses that produced both SARS and MERS — watchers are hoping that Chinese authorities will provide additional information soon.


“I think we need to give them a couple of days but I want to hear something from a credible source on the investigations that are ongoing,” said Marion Koopmans, director of the department of virology at Erasmus Medical Center in Rotterdam, the Netherlands.

As of Friday, health authorities in Wuhan reported 44 cases, a big jump from the 27 reported on Tuesday. Eleven of the 44 were seriously ill, the Wuhan Municipal Health Commission said, though there were no reported deaths to date. The health of 121 close contacts of the cases was being monitored. The infections are linked to a large seafood market where it is believed some exotic animals were also sold for consumption.

The World Health Organization has said little about the outbreak beyond that it is in close contact with China authorities on the issue.


“We’re closely monitoring the situation in Wuhan and are in active communication with our counterparts in China,” WHO’s regional office for the Western Pacific Region, which includes China, said on Twitter. “We’ve activated our incident management system across the three levels of WHO (country office, regional office, HQ) and can launch a broader response, if needed.”

The agency noted that China “has extensive capacity to respond to public health events and is responding proactively and rapidly to the current incident in Wuhan — isolating patients, tracing close contacts, cleaning up the market, and searching for the cause and for additional cases.”

Ralph Baric, a coronavirus expert at the University of North Carolina, agreed that China has deep expertise in virology. Baric has a collaborative grant with some researchers in Wuhan to study emerging coronaviruses, and has visited the facilities there.

“Wuhan is the epicenter for a lot of virology research in China. They have state of the art BSL3 and BSL4 facilities and world-class facilities to do anything that you would want to do on new emerging infectious diseases. So it’s occurring in the right spot,” he said.

BSL is shorthand for the bio-safety level designation of a laboratory; level 3 and level 4 are the labs in which the most dangerous pathogens are worked on.

Social media platforms — both in China and outside it — have been abuzz with discussion of the Wuhan outbreak, with some commentators arguing the lack of a clear answer by now is reminiscent of China’s behavior during the 2002-2003 SARS outbreak.

But Baric disagreed, saying China’s approach to infectious disease outbreaks has evolved considerably since SARS, an event for which it was harshly criticized globally.

“The situation in China between 2003 and 2020 is night and day,” he said. “They have many of the best virologists in the world there that are working on this. And my gut feeling is we’re going to see a showcase of what they’ve accomplished in 20 years.”

Koopmans and Baric have a number of questions they’d like answered — “very soon,” Koopmans said — to help assess the severity of the situation.

Knowing whether Chinese scientists have identified the cause of the illness is top of the list. Whether it is indeed a new virus — and what viral family it belongs to — is right up there too.

During the SARS outbreak, it took a full month from when the WHO tasked a global network of 11 laboratories to find the cause of the outbreak before confirmation was received that a new coronavirus was the culprit. The SARS coronavirus probably originated in bats, but civet cats — wild animals eaten as a delicacy in southern China — were the virus’ route to people.

Technology has improved a lot since then, said Baric, who said multiplexing PCR — polymerase chain reaction testing — and RNA-Seq, which looks for evidence of the RNA of pathogens in clinical samples, could make finding the culprit a much quicker job this time round.

But even with the new technology, finding the cause of pneumonia can be tricky. With some infections, by the time a person is evidently ill, their immune system has cleared away most of the causative agent. The symptoms of illness are actually the effect the cascade of immune system weapons unleashed on tissues that had been infected.

“There’s a window there of viral detection of the viral nucleic acid,” Baric said.

“If most of these initial patients were caught late in infection, when the more severe disease symptoms came on, they may not have any acute cases and it may be very difficult. Very low levels of nucleic acid to chase to discover the disease.”

Koopmans noted finding the cause may be complicated by the fact that pneumonia is common and can be caused by many pathogens. If authorities started looking for pneumonia cases after realizing there was a problem in Wuhan, some of the cases they found might have been unrelated to the actual event.

Both are keen to know if there is any spread of the illness between people, which would be worrying. Wuhan health authorities have said there was no human-to-human transmission. But unless they know what is causing the illness, how long the illness takes to develop, and have developed a test that can detect mild cases, it is not clear that can be ruled out at this point.

“I don’t find the comments [about human transmission] that I see spread throughout the internet as credible — unless they know what it is,” Baric said.

The fact that health officials in Wuhan closed and decontaminated the seafood market — there is video of this happening on social media — is suggestive that an animal virus had spilled over into people, he added.

The statement from the Wuhan health board said that influenza, avian influenza, and adenovirus infections — the latter can cause serious respiratory illness — have been ruled out.

Because of SARS, attention is focusing on coronaviruses, though both Koopmans and Baric noted a number of different virus families could cause respiratory outbreaks.

But coronaviruses have shown themselves to be adept at jumping from animal hosts to people, sometimes establishing themselves as human pathogens. There are four human coronaviruses that are common causes of cold-like illness. Those viruses were formerly animal viruses — experts can tell by comparing their genetic sequences to animal coronaviruses. When the four started infecting humans is not clear in most cases.

Some coronaviruses have jumped from animals to people on multiple occasions — the MERS virus in the Arabian Peninsula is an example — but haven’t acquired the ability to spread easily from person to person.

Sometimes the damage can be significant.

In late November of 2002, people in the southern Chinese province of Guangdong started to become ill from unexplained pneumonias. The WHO began hearing rumors of the illness, but Chinese authorities played it down.

But in late February, travelers from a number of countries — Vietnam, Singapore, Canada among them — stayed on the same floor in a Hong Kong hotel as a doctor from China who had been looking after some of the pneumonia cases. He was ill, and he infected multiple other hotel guests, seeding the new infection across Southeast Asia and to Toronto.

Transmission of the new disease was stopped by the summer of 2003, but in its short history SARS — short for severe acute respiratory syndrome — infected more than 8,000 people and killed nearly 800.

Baric said he’s hopeful Chinese scientists will have figured out what is going on in Wuhan and will report on it soon.

“If the number of cases keeps increasing, then it becomes more and more of a global public health threat,” he said. “The chance of [infected] people slipping through the screening platforms for international travel or travel elsewhere in China become greater as long as they don’t know what the pathogen is.”

  • As indicated on the first day of media reporting, the reporting signal pattern did not match SARS or MERS. As healthcare providers, we are mindful of signs and symptoms that prompt us to think of a certain disease. Very much the same is true for how people talk about outbreaks in media and official reporting- this speaks to the discipline of analysis as it pertains to health security. We have to pay attention to both the clinical *and* the reporting features. Local officials have now indicated they ruled out SARS and MERS ( We’ll keep an eye on what the final assessment is here- a very interesting case study.

    James Wilson, MD
    M2 Medical Intelligence

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