An influenza test for whether lockdowns work

By Chris Gillham

As one of the audit team for Jo Nova’s blog, I have been looking at the question of whether lockdowns work and their potential suppression of communicable diseases other than COVID-19.

Since the current pandemic only began killing people this year, there is no previous year with which it can be compared. However, lockdowns – to the extent that they work – will work not only against the current COVID-19 infection but also for other viral infections.

Take influenza as an example. The World Health Organization monitors positive and negative influenza notifications from laboratory tests in various countries (https://www.who.int/influenza/gisrs_laboratory/updates/summaryreport/en/), and this seems to be about the only up-to-date data on their website. So we can compare the flu test results in relevant post-lockdown weeks in 2020 with flu results in 2019 to see whether there is a marked difference.

Since the WHO publishes them, it might be assumed that these laboratory test results have some correlation with community influenza numbers in the different countries.

I have selected 17 countries based partly on their population size and prominence over the past few weeks in the COVID-19 crisis, and partly on whether or not they supplied sufficient weekly reports within the timeframe. My analysis starts in week 14 of 2019 and goes to week 18 of 2020, which was at the end of April. Their total influenza test positives can be presented graphically but are constrained by the most recent notifications, the US a laggard with its last notification in week 14 2020.

Fig. 1 shows flu positives in 11 countries with the most up-to-date data from week 14 of 2019 to week 18 of 2020. The significance of this graph is that normally the worst of the winter flu epidemic is over by week 14.

However, separate figures for excess deaths in weeks 14 to 18 of 2020 compared with the average for the previous five years in Britain and Europe have shown a spike well above the normal excess deaths for those weeks. The likelihood is that most of those excess deaths were caused either by the SARS-COV2 virus itself or by consequences of the lockdowns, such as a sharp reduction in normal surgical interventions.

Compare directly the flu positives for weeks 14-18 of 2020 with the corresponding weeks from 2019. For the same 11 countries, over those five weeks the number of flu positives was just 1,550 in 2020, but it was 12,934 – more than eight times greater – in 2019. That 88% reduction in flu positives is an indication that the lockdowns may be inhibiting the usual transmission of flu:

Looking just at week 14, six more countries can be added. Then the 2020 reduction is 90.9%:

The difference between reported flu positives in 2019 and 2020 becomes still more stark if the analysis is confined to the 14 countries meeting our criteria that have updated their data to week 17 of 2020 (Fig. 4):

Here, the reduction in positive laboratory influenza test notifications over the two comparable periods is an impressive 92.6%.

Naturally, there are many confounders. Ideally one would want to average the previous five years’ data for weeks 14-18. And one would want to discover whether under-reporting of flu cases has increased because health personnel are busy coping with the pandemic. Nevertheless, the figures suggest that lockdowns do achieve their primary purpose, which is to reduce the transmission of infections.

As more data become available, it will be possible to make direct comparisons between both cases and deaths from flu and from the new infection. From the point of view of ending lockdowns, the comparison should be age-based because it is possible that for those under 60, and certainly for those under 50, the new infection is less fatal than flu.

It’s worth a closer look at influenza test positive results from several countries:

The Russian results are an interesting outlier because Putin didn’t get serious about a lockdown until late March. That is a good indication that lockdowns work well and are the easiest to bring to an end if they are imposed early.

Russia’s flu positives were 537 in week 14, 231 in week 15, 99 in week 16, 47 in week 17 and 10 in week 18, from which I deduce Russia should soon start reporting a reduction in COVID-19 cases.

However, the UK and USA have been criticised for a perceived slow lockdown reaction to COVID-19, and Sweden had a 95.7% reduction in positive influenza test results comparing weeks 14-18 in 2019 and 2020 (1,541 > 67) despite only a partial lockdown.

Ignoring numerous other confounders such as population age and density, these discrepancies suggest some questions might be asked about the efficacy of lockdowns. However, laboratory flu test results from most countries indicate that social isolation has suppressed the spread of communicable diseases other than COVID-19, and this logically is evidence that lockdowns have done the same with the coronavirus itself.

These results cover just over a third of the world’s population from 17 different countries.

Therefore, if positive laboratory influenza tests are a moderately accurate reflection of infection percentages in their broader communities, and if influenza is a common indicator of community infection among the several dozen other communicable diseases, it might be said that the COVID-19 lockdowns have resulted in a ~90% reduction in global infections.

It may prove to be a lower percentage reduction, possibly dependent upon learned social distancing practices after lockdowns are lifted and the spread speed of different diseases, but the WHO influenza evidence suggests lockdowns have public health benefits beyond the targeted COVID-19.

• I am grateful to Lord Monckton for assistance in preparing the graphs.