According to HM Government and the NHS, one in three people have no COVID-19 symptoms and are spreading the virus without knowing it.

Look, it says so here in this expensive full-page ad that they ran in daily papers last week:

It’s not true, of course. The NHS you’ve been clapping and protecting these many months is – and there is no gentle way to say it – lying to you.

For some reason, the huge brains on the Government’s Independent Scientific Pandemic Insights Group on Behaviours (SPI-B), who oversee this kind messaging, decided to omit four crucial words from the first sentence:

“…who have the virus”.

If you apply that Very Important Qualifier, as the government does except when it’s buying high profile advertising space, the alleged prevalence of asymptomatic transmission (AS) shrinks. By a Lot.

Those four words demote the risk of AS from the NHS’s positively terrifying 1 in 3 to a rather more reassuring 1 in 180. I mean, how long does it take for most of us to get within six feet of 180 other people these days?

Short mathematical interlude

What is the gap between the NHS ad and reality? In real life the number estimated to have the virus at any time in the UK is around 1.1 million. A third of that number is 370,000. That equates to one in 178 people. Not remotely close to 1 in 3. Someone should report the ad to the Advertising Standard Authority. Oh, I just did 👮🏻‍♂️.

Why exaggerate like that?

That’s the question a lot of folks have been asking ever since they learned that Professor Neil Ferguson was part of the solution. That’s like having the world’s biggest whaling ship as part of your marine conservation programme.

Every prediction about the virus comes with its own generous dollop of dire. So long, that is, as dire sells whatever policy the government intends to pursue over the next days or weeks. When they want good news, the public service ads will spin the figures in the other direction, just watch.

For now, the government-approved goal state of mind for you and me is cowed, fearful and guilty. Of course, that is hard to achieve when you see sprightly joggers, apple-cheeked mothers and healthy-looking elderly dog walkers all over the place.

Which is where asymptomatic transmission comes in. For obvious reasons these days, you never meet anyone with symptoms because they stay at home at the first sign of a sniffle or tickly throat. But if one in three of everyone else looks healthy but is secretly spreading the virus, then bingo! You’ve got SPI-B’s viral remake of Invasion of the Body Snatchers.

From rare to rampant overnight

Nothing is perfect, though. One drawback to using asymptomatic transmission as a way of keeping folks obediently fearful (a SPI-B objective, by the way) is that AS of Covid-19 is still not very well understood. For all the millions of “cases” around the world, there isn’t a lot of data on how easily and how often Covid is passed on by infected people with absolutely no symptoms.

Serendipitously, a week or so before GOV.UK launched its secret spreader ad campaign, “new research” popped up. “Most COVID-19 Cases Caused by People Without Symptoms” is typical of the headlines garnered by the study published by the ostensibly authoritative Journal of the American Medical Association (JAMA).

New research has found that over half of COVID-19 cases are likely caused by people without symptoms.

Approximately 59 percent of all transmission is caused by pre-symptomatic individuals who hadn’t yet developed symptoms and asymptomatic people who never developed symptoms, according to the study.

The researchers say the findings show how identifying and quarantining symptomatic patients isn’t enough to control the rapid transmission of COVID-19.

Strict public health measures – including mask wearing and physical distancing – and widespread testing of people without symptoms is necessary to identify people who have COVID-19 and who may be silently transmitting the coronavirus. (Source) (My emphasis)

Well, that sounds pretty conclusive. New research. Published in a peer reviewed journal. Showing that nearly two-thirds of infections come from asymptomatic individuals. Batten down the hatches!

Except… One should never take medical research stories at their face value. See the entertaining but damning book, Doctoring Data: How to sort out medical advice from medical nonsense, by Macclesfield-based GP Dr Malcolm Kendrick. Then sigh heavily and take a peek at the original paper. behind any media article. Chances are that, even if like me you’re not an expert, Dr McKendrick’s book will help you spot anything that should set off alarm bells.

And there are a quite a few in the asymptomatic transmission study. For starters, the label “research” suggests the authors directly measured relative transmissibility among human subjects. Nope. They did a computer modelling exercise that “involved no enrolment of human subjects”. The authors don’t claim much for their method either: “…we used a simplistic model to represent a complex phenomenon”.

What’s the meta, baby?

An obvious danger here is garbage in, garbage out. Though they didn’t feed it garbage exactly. But they did take all their starting assumptions for the model from eight studies done in and around China at the start of the pandemic nearly a year ago. Or rather from “a rapid systematic review and meta-analysis of observational research” of those eight studies. That’s three of Dr Kendrick’s red flags in one sentence.

Despite the confident assertion that 59 per cent of infections come from asymptomatic transmission, there is actually no new or unequivocal evidence behind the claim. The authors made a simple computer model, into which they fed guesstimates, which were based on reviews of meta-studies of analyses of data that in, most cases, merely inferred asymptomatic transmissibility from public health data.

The one source which directly monitored symptomatic and asymptomatic patients in a clinical environment did not identify examples of asymptomatic transmission. It found that most patients with no symptoms had viral loads similar to those with symptoms, suggesting they might be equally infectious, albeit without the coughs and sneezes that viruses love to travel on. But the study couldn’t isolate specific cases of no-symptom transmission.

Apocalypse Not Exactly

I focused on the above paper because it’s recent – 7 January 2021 – and because it perfectly illustrates how headline figures like ‘59 per cent’ frequently turn out to derive from guesstimates based on assumptions based on meta studies based on long-ago observations.

Moreover the “Fact Checked” tags that the media slap on to their reports of the study are meaningless. They only mean that the checker checked they reported the study accurately, not whether the study itself amounted to a hill of beans or a pile of something quite different.

We’re now a year into the UK’s coronavirus epidemic and still no-one from WHO downwards can claim to have a good handle on how often and how easily asymptomatic transmission occurs. There is certainly no basis for the government and NHS to claim that a third of people with the virus are silently spreading it, let alone that a third of ALL people are. Bloody liars.

Anecdotally, I’m aware of asymptomatic transmission between NHS ward staff occurring during prolonged close contact in staff rooms and when sharing lifts in cars. It is less likely on the wards themselves, where staff are PPE’d up and being ultra-careful with patients and each other. At least one trust has prohibited staff from lift sharing to reduce the number off work and isolating due to positive tests.

So yes, AS is a thing. But it probably doesn’t happen often when two friends meet for an outdoors walk in the middle of nowhere, whether or not they’ve brought along flasks of tea. Does happen quite a lot in hospitals, though. Physician heal thyself and all that.

The bottom line is that, even if the latest UK government and NHS ad campaign didn’t exaggerate the likely number of alleged asymptomatic spreaders by a factor of sixty, there is still a very long way to go before there’s enough scientific consensus on asymptomatic transmission to justify using it as the basis of a blame and shame campaign directed at a public that is largely doing its best.

But blaming us may be the only thing left to do.