Update on 2019-nCoV: part 9 – ‘silent’ transmission

A rude awakening this morning: “Study claiming new coronavirus can be transmitted by people without symptoms was flawed” was reported in Science. This is the patient described by German colleagues in NEJM and by Jon in the previous blog post.

The story in short: An index patient (a woman from Shanghai) was visiting Germany for business, and managed to transmit the coronavirus to two patients, who subsequently transmitted the virus to two other colleagues, before symptoms arose (in the index patient). The story was reported by hospital physicians from Munich and a virologist from the Charité hospital in Berlin (where the famous Robert Koch once worked).

In Science: “The Robert Koch Institute (RKI), the German government’s public health agency, has written a letter to NEJM to set the record straight, even though it was not involved in the paper.”

The researchers in Munich didn’t actually speak to the woman before they published the paper. “Afterward, however, RKI and the Health and Food Safety Authority of the state of Bavaria did talk to the Shanghai patient on the phone, and it turned out she did have symptoms while in Germany. According to people familiar with the call, she felt tired, suffered from muscle pain, and took paracetamol, a fever-lowering medication.”

When reading this I recalled two dreams I had this night.

Somewhere – in a not-mentioned country – physicians were very excited as the first patient with disease X had fallen in their lap. “Let’s first send this to NEJM and then contact our public health officials, otherwise they run away with it.” The day after – at the other site of the country – the NEJM fell on the floor in the oval office of the head of public health – responsible for the nations’ faith. He/she contacted the index and found out that she – in retrospect and after 20 times repeating the same question – admitted that “yes, she felt tired, had some muscle pain and took a paracetamol”. “That’s it”, he/she shouted, “this is the perfect call”, “READ THE TRANSCRIPT!” and called Science.

The other dream: Somewhere – in a not-mentioned country – physicians were very excited as the first patient with disease X had fallen in their lap, and they immediately contacted the head of public health – responsible for the nations’ faith. “Let’s first send this to NEJM and then contact the index. Might give us 2 citations in NEJM.” The day after the NEJM fell on the floor in the oval office of the head of public health and he/she contacted the index and found out that she – in retrospect and after 20 times repeating the same question – admitted that “yes, she felt tired, had some muscle pain and took a paracetamol”. “That’s it”, he/she shouted, “this is the perfect call”, “READ THE TRANSCRIPT!” and called Science.

Then my alarm went off, and I couldn’t dream of other, more realistic scenarios.

The big question now is whether our view on the transmission dynamics of this outbreak should change with this new information. The point of silent transmission, i.e. before symptoms occur, is that it will be more difficult to identify infectious persons and isolate them in time to interrupt transmission. The symptoms reported in retrospect (when knowing of being indeed infected, susceptible to recall bias!) were “tiredness and muscle pain”. Cough and fever are not mentioned. If this is what it is, then this woman might still have been identified of being at risk for 2019_nCoV infection in Germany, simply because she came from China. Yet, in Wuhan this would probably not be recognized as a risk, necessitating isolation. And the same would hold if sustained transmission occurs in other countries.

So, this information sheds new light, and addresses the definition of being asymptomatic. If symptomatic would be defined as “symptoms that allow someone to be recognized as infected and to be isolated in time to prevent transmission”, I think, this subject would be considered asymptomatic.

The letter from RKI has not yet been published. The Science reporting is based on someone who was in the room during the phone call (sweet irony).

Disclaimer: if the letter describes a feverish Chinese woman coughing continuously, I immediately change some of my views.

One thought on “Update on 2019-nCoV: part 9 – ‘silent’ transmission

  1. Hello Marc, so if we were to state that transmission is taking place without respiratory symptoms, would that not point to the possibility of airborne transmission? Droplets do not travel very efficiently through the air without the force of the cough. I would like to compare it to varicella; children with blisters but without respiratory symptoms still transmit the virus through the air. There too, a number of children have changes on chest X-rays but no respiratory symptoms. Something that was also described in the novel corona virus.

    Like

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