by Tom Chivers
Friday, 30
October 2020
Explainer
07:00

The real reason flu cases are falling

by Tom Chivers
Flu jabs: as pleasant in the 50s as they are today

A strange little conspiracy theory is going around in parts of the internet. They’ve noticed that flu cases are way down — a September paper from the US CDC reckons by 90%, while this piece makes an (unsourced) claim of 98%. And they have decided that this is because flu cases are being misdiagnosed as Covid. The ur-conspiracist David Icke himself is on board with this one.

To be clear: it’s not true. It is inconsistent with how flu and Covid cases are counted, and there is a much simpler explanation, which is that the measures we’ve taken to counter Covid are also effective against other respiratory diseases. But it has got quite a few people talking about it, and some of the tweets about it are doing fairly big numbers.

Here’s why it’s not true. First, the prevalence of Covid — in the UK, at least — is estimated using tests which look for the presence of RNA from the SARS-Cov2 virus. For instance, on Thursday the REACT-1 survey estimated that around 1.3% of the UK population has the virus. It does this by sampling the population at random, as in an opinion poll, and extrapolating from that. The ONS infection survey does much the same thing.

Similarly, flu prevalence is estimated by taking laboratory-confirmed cases and extrapolating from that to provide an estimate of the total in the population. The two are entirely different kinds of virus — SARS-Cov2 is a coronavirus, flu an influenzavirus — and there just isn’t a way that a test for one could be triggered by the presence of the other. The CDC estimate, mentioned in the first paragraph, is based on positive laboratory tests. That would not be affected by how many Covid tests had come back positive.

The CDC paper says that early on, people thought it might have been because fewer flu tests were being done — due to people with respiratory illnesses being sent for Covid tests — but “renewed efforts by public health officials and clinicians to test samples for influenza resulted in adequate numbers tested and detection of little to no influenza virus”.

Of course, that doesn’t explain why the flu cases appear to have gone down so much. But that seems fantastically non-mysterious to me: the two diseases are spread by similar means, so the measures we take to slow the spread of Covid-19 (masks, lockdowns, travel restrictions, etc) will also slow the spread of flu.

Flu is less easily transmissible than Covid-19 — I’ve just looked at a bunch of studies and they all broadly agree with this one which estimates that a new flu strain has an R of between 1.4 and 1.6, compared to about 2.6 for Covid. If wearing face masks reduces R by 0.7, doing that on its own would only slow the spread of Covid while it would cause flu to (eventually) die away. It could easily be that the measures we’ve taken haven’t been enough to stop Covid but have had a huge impact on the flu season.

There may be other things going on, but I think (as does the CDC) that is the likeliest explanation. It’s just not plausible that people are counting flu cases as Covid.

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  • I have adopted a different approach when looking at Covid stories/narratives. If someone is a proven real scientist with a track record i listen. Journalists/people with a humanities background i don’t listen to. I have found my life has become a lot calmer as i watch the surrounding madness!

  • Or even the non-mysterious way is that the people who would normally be taken by flu etc are going on the Covid pile….I get your logic and you could be absolutely right (although I hope not because there are people stupid enough to think that mandatory mask wearing should be here to stay). As for the benefits of mask wearing, I would rather wait to see the recent Danish study (that oddly nobody wants to publish) before we decide if they work, and even if they do, wont they diminish our immune systems over the long term causing even more problems down the line.
    I have always wanted the best option for the most amount of people, that will probably involve making some uncomfortable but brave calls, but I don’t trust any of these cowards in government to do anything other than take the easy option based on single issue thinking from SAGE, dodgy polling and/or pressure from the msm.
    The most depressing spectacle for a layman is watching these supposed experts all over the place with their data, surely the WHO should have standardised every countries methods to get a clear picture so as to formulate an effective response, they are FIFA for health.

  • Or it could be that there are a limited number susceptible to complications from respiratory illness each year and Covid is merely bearing flu to the end line.

    Otherwise it seems a fortuitous coincidence that we have reduced flu to just the levels needed to keep deaths from respiratory infection no higher this year with covid than they were last year without it (for this time of year).

    I think there was a similar finding made in 2009 in relation to the interaction between swine flu and rhinoviruses.

    Just something else to consider, the social distancing might be working for flu as well (or instead – doesn’t really seem to work for Covid).

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