6th April 2020 – Asymptomatic Carriers of the COVID-19 Virus are Key to the Solution 


A Blog by Dr David J Flavell PhD FRCPath
Charity & Scientific Director of Leukaemia Busters

6th April 2020


One of the most important aspects of continued transmission of the COVID-19 virus that has not been talked about much in public briefings is the existence of “carriers”, people who have no symptoms of infection but who are able to transmit infection to others because they are shedding active virus in their saliva, nasal secretions, tears and even in their faeces.

Without appropriate mass testing it is impossible to detect these individuals in the general community and they remain a walking risk to others, hence the importance of self isolation, social distancing and sensibly you might imagine the use of face masks (see my blog from the 3rd April, Unmasking the Myths) when out and about shopping, exercising or at work. The data from the Cruise ship Diamond Princess where 712 individuals became infected showed that 331 (46.5%) of these had absolutely no symptoms, they were effectively carriers. 

The only real solution to the carrier issue is to mass test the entire population and aggressively isolate those who are identified to prevent them from further transmitting infection. This strategy may have to be implemented over and over to screen and re-screen to stamp out the transmission cycle. The big problem with this particular strategy is the current lack of sufficient testing capability, it would mean ramping up PCR testing from tens of thousands per day to millions per day, a tall order. For a useful video news item explaining about carriers of the virus see the video link below.

In addition to the carrier problem there are also a proportion of individuals who have recovered from COVID-19 but are still shedding active virus maybe for many days or weeks after apparently making a full recovery. Studies from Wuhan have shown that up to 14% of recovered COVID-19 patients continue to shed virus with one reported case up to 49 days later.

This creates a massive problem for people returning after having COVID-19 to work on the front line in healthcare where testing for shed virus should be undertaken as a mandatory requirement before they face patients or colleagues. The same goes of course for the general population but it is perhaps more critical in the healthcare setting in terms of inadvertent transmission by returning medical staff within hospitals and clinics.

That said I was pleased today to see that Professor Chris Whitty, the Chief Medical Officer had recovered from COVID-19 and was taking part in the No 10 briefing session to journalists and the British people. I wonder however, and nobody from the media asked the obvious question, had he been re-tested by RT-PCR (not the antibody test) to determine that he was no longer shedding virus? If not then there’s the possibility that he is a carrier and is therefore still infectious posing a risk to anyone in close proximity. Dominic Raab was right there alongside him. We really don’t want the designated successor to Boris Johnson and potentially other key people in No 10 also disappearing off the scene with this illness do we now?

I’ve just heard that The Prime Minister has been admitted to intensive care at St Thomas’ Hospital across the river from Westminster and I fear for his well being. I wish him a quick and full recovery so that he is able once again to lead the government in the nations fight against this disease.

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