Myths, misunderstandings and misinformation on covid-19

Everyone should be wary of myths and misinformation about covid-19, and aim to combat them via accurate information.

Myths and misinformation are common on the internet, e.g. a study by the UK fact checking charity Full Fact found that of 96 Facebook posts, only five were rated as true - read a summary article in the British Medical Journal [1], or the original report [2].

Myths, misunderstandings and misinformation

"The reported deaths are deaths from any cause within 28 days of a positive test so many had absolutely nothing to do with covid-19"

The reality:
The excess mortality in March/April was about same as the recorded covid-19 deaths. There will be some deaths within 28 days of a positive test that were due to other causes, but there will also be other deaths due to covid-19 that were not included because the person was not tested, or because of a false negative, and it seems that these roughly balance.
So we should take current recorded deaths as fair estimate of deaths from covid-19.
Sources and more details are here.

"PCR testing for covid-19 has too many false positives for it to be useful"

The reality:
The false positive rate is so low that PCR testing can be used to monitor epidemics and treat patients:
  • Circulating figures of "0.8-4%" are wrong - they come from a literature survey of research on other RNA viruses carried out between 2004-2019 and are no longer relevant [3]
  • Countries with the best control of the virus have rates of positive tests of less than 0.1% (e.g. New Zealand, Australia and Singapore) [4]. So the false positive rate must be less than 0.1%.
  • There is a strong association between reported cases and reported deaths. Countries with an outbreak of the virus have a rise in reported deaths form covid-19 about 3 weeks after the rise in reported cases - with deaths defined, for example, as a death where covid-19 was felt by the clinicians to be a factor in someone who had first tested positive less than 28 days before death. When an outbreak is contained, and the reported cases peak and then fall, the reported deaths also peak and fall, with an interval of about 3 weeks between the peaks. Examples include New Zealand and Australia [5].
  • Many countries e.g. South Korea have used testing to control or eliminate their outbreaks of the virus (in conjunction with tracing contacts and isolation). How have they done this if testing is not reliable?
  • Read more in a Full fact article [6]

"Kary Mullis, inventor of the PCR test, said …XYZ"

The reality:
A Full Fact investigation found there has been much misquoting of Kary Mullis [7].
Whatever he said, the method has since been developed and has been fundamental to countries eliminating their outbreaks (read more).

"The cases/admissions/deaths are low and so no action is needed"

The reality:
It's not the level of cases that matters but whether the rate per day is increasing or decreasing and how fast.
Epidemics tend to grow exponentially (i.e. with a constant doubling time) until control measures are changed, and tend to decline exponentially (i.e. with constant halving time) until control measures are changed.
If an epidemic is growing it will continue growing until health services are swamped or until control measures are introduced. So there is no point in delaying measures - it is just putting off the inevitable and incresing the health and economic damage.
It is like a cancer or a forest fire. If we spot a cancer growing, we don't say "it's small, the body is coping with it, let's leave it until the patient is seriously ill. And with a forest fire, we don't watch it growing until forced to act - we eliminate it as soon as possible.

"The only way to measure rates of covid-19 is to do random sampling or whole population testing"

The reality:
In general, random sampling is needed to assess disease prevalence, but with covid-19, most cases have symptoms, and without restrictions, the virus spreads rapidly and does not stay hidden for long, so we can be confident those areas reporting zero cases do actually have none.

"The more you test, the more positives you will find"

This can be stated, when reported cases are rising, as an pretext for taking little or not action.
The reality:
  • Yes, more testing will lead to more positives being found where only a small proportion of cases are currently being detected,
  • a few more cases will be found by more testing where most cases are already being detected,
  • No, more testing will not lead to more positives where all cases are already being detected.
In comparisons between territories, and in comparisons at different times in the same territory, differences are so large or so rapidly changing that they are rarely entirely due to differences in testing.
Further information: the section on testing on the Our World in Data webpage [8].

"We have to learn to live with the virus"

The truth: The virus can be eliminated in the same way as outbreaks of the Ebola virus and the SARS virus have been eliminated. Several countries have eliminated the virus, with the only new cases being incoming travellers - this requires quarantining and vigilance. Examples are New Zealand, Vietnam, and Taiwan (read more).

[1]Sixty seconds on...Fact checking (2019) BMJ 2019;366:l5017
[2]Full Fact Report on the Facebook Third Party Fact Checking programme: Jan–Jun 2019
[4]Our world in data: The positive rate (viewed 20.10.20)
[6] (viewed 20.10.20)
[7]The inventor of PCR never said it wasn’t designed to detect infectious diseases (23.10.20)
[8]Our World in Data: Coronavirus Pandemic (COVID-19) (Updated daily)

First published: 28 Jun 2020
Last updated: 30 Oct 2020