Crucial Report Claiming Coronavirus Transmittable Before Symptoms Appear May Be Wrong

A report in one of the world's most prestigious scientific journals of asymptomatic transmission of Wuhan coronavirus, 2019-nCoV appears to have been made in error, leading scientists to question if the new virus spreads as easily as feared.



For obvious reasons, it is much, much harder to control the spread of a disease that can be transmitted by people who don't show any symptoms. People with many sexually transmitted diseases can be infectious for long periods while never getting sick themselves. For other diseases, the infectious period can precede the first symptoms. Either makes for a public health nightmare.

Consequently, when a new disease emerges, one of the first questions is whether it can be spread by healthy people. So when a letter in the New England Journal of Medicine (NEJM) traced the first four German 2019-nCoV infections to someone without symptoms it was news no one wanted to hear, but needed to act on.

Now, however, we're back to square one, with crucial new information challenging the conclusion.

On January 20 and 21 a woman from Shanghai visited the head office of a German business partner. Two people she met with subsequently became ill and tested positive for 2019-nCoV, along with two of their colleagues who never met the woman directly. The NEJM letter reported that those who met her said the woman showed no signs of being sick at the time, but had them alerted after developing symptoms of the new virus on her return flight, and testing positive at home.

Although Chinese health officials had indicated the possibility of asymptomatic transmission previously, these reports had been tentative. Now things seemed definite. Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, said at the time: “This study lays the question to rest.”

However, a crucial step had been missed: no one involved with the letter had been able to reach the woman to ask when her symptoms started.

That's now been rectified. In a phone call with the Robert Koch Institute (the German government’s public health agency), she confirmed she was already showing symptoms prior to her German meetings. The Insitute contacted the NEJM, leading to some of the authors admitting they moved too fast, although the paper has yet to be retracted. Science Magazine reports people with knowledge of the call say she felt tired and took paracetamol for muscle pain, although this has yet to be officially confirmed.

This doesn't mean we now know asymptomatic transmission can't occur, just that it didn't this time. Moreover, muscle pain and tiredness are common, particularly after an intercontinental flight. Even if symptoms like these are a prerequisite for infection, screening will remain exceptionally challenging – but still much easier than if there may be no signs at all.

In particular, drastic moves like quarantining all Chinese visitors would look deeply questionable.

The subsequent information points to the dangers of racing to publish in the middle of a rapidly evolving crisis. The same day saw the retraction of a paper on the pre-print site bioRxiv that claimed to find similarities between 2019-nCoV and HIV. Pre-print sites host papers that are in the process of being peer-reviewed. While some may never pass this process, it is generally assumed they have some basis in fact, but the paper bioRxiv withdrew implied the new coronavirus had been genetically engineered. Such a claim, as well as being baseless, would likely lead to more fearmongering and racism were it widely disseminated.

The contrast between this process and the circulation of conspiracy theories of the virus' origins or claims drinking bleach or homeopathy will protect you is dramatic. Scientists are human and also get it wrong – but the scientific process means these errors get called out or owned and corrected, which in this case occurred just four days after publication.

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