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Consequences of actions

I have read an interesting and challenging post by Robin Phillips who asks two very important questions:

(1) How will the coronavirus eventually end? (2) Is it possible that the damage caused by the containment measures and shutdowns could end up doing more harm than the virus itself?

so here is my personal perspective on these two challenges, particularly as both involve the type of mathematical modelling I am very interested in.

The questions are challenging because they involve predicting the future in which our current actions in reaction to these predictions change the course of action. They also involve our limited understanding of how very complex epidemiological, economic, social and psychological systems work.

We now have a reasonably good understanding of how fast the virus spreads which makes short term predictions possible – assuming the way it all works does not change. As for long-term predictions, they are notoriously difficult to make.

There is a worst-case scenario which assumes that everybody or nearly everybody will become infected leading to massive casualties. This is based on the current estimates of the rate of spread plus realisation that what we see as reported cases is a tip of an iceberg – in other words, that there are actually many individuals who spread the disease but somehow escape the attention of the health authorities – perhaps because they have very mild symptoms. This is known as under-reporting and judging from other outbreaks (going back to measles in 1960s) can be as high as 90% (i.e. we only see 10% of cases). This case is worrying because it means we are already past the stage when we can actually do something to stop the disease from spreading and so the only thing we can do is to flatten the epidemic curve i.e. to slow down the spread so that the health system is not overwhelmed.

There is another factor that worries the authorities, that the virus might become endemic. This means that we will never be able to eradicate it completely and so it will keep coming back in the years to come. I do not know exactly the thinking behind what emerges as the UK strategy centred on reaching herd immunity, but I suspect it is the combination of three factors: (i) the conviction that we are past the point when we can stop the disease, (ii) the assumption it will keep coming back, and (iii) the estimation that costs of a massive lock-down are immense and the outcome uncertain.

I am personally not fully convinced about these assumptions. As for (i), China and South Korea examples show that it is possible to stop the disease from spreading. The implementation of various control measures, some very drastic, reduces the rate at which infection spreads and leads to local eradication of the disease. This is becoming known as the continental strategy as it has been implemented by Italy and most other EU countries.

I am even more suspicious about (ii). This is a very infectious virus with a high rate of spread and so is likely to go through the population quickly and to burn-out. Evidence from past epidemics (like measles or flu) and modelling suggests that for such virus to persist it would require a massive population well exceeding the size of the world (what we call critical population size). The closest analogy is flu, but it is a flawed analogy as each year flu comes and goes and disappears, but what comes back next year is a genetically different virus (so really, a new epidemic); thus, technically speaking flu does not persist in humans.

The only possible explanation supporting point (ii) is that unlike flu, the coronavirus might not make people immune. I do not know the current state of knowledge in this area, so it is possible that the UK government scientists know something I do not.

As for (iii), it is really a matter for the governments – and people – to decide what is the balance of costs and benefits. Science can only assist by presenting different scenarios and estimating – very broadly – the costs and benefits of each strategy. I suspect that the governments in the continental Europe countries feel the EU will help financially if needed (as it already does) and the UK government feels that it cannot afford to spend billions on helping the businesses to survive the lock-down. But, it is only my own opinion.

I believe there is actually an even worse scenario in which the governments go part-way, so impose a partial lock-down which causes massive (but not extreme) economic losses but fails to stop the epidemic. Something like this was apparently happening in the late stages of the 2001 foot-and-mouth epidemic which resulted in huge losses and a very long tail of cases, as seen below in figures (c) and (d) (another example of whack-a-mole strategy) [from Science  26 Oct 2001:Vol. 294, Issue 5543, pp. 813-817; DOI: 10.1126/science.1065973 ]:

Foot and mouth 2001 outbreak

I think the next couple of weeks will tell which strategy works (or whether both fail) and what is the future of the coronavirus outbreak. As an epidemiological modeller, I find the emergence of the two control strategies fascinating (see my earlier posts), but as a human being taking immuno-suppressing drugs and hence at high risk from coronavirus, I find it a bit disturbing.

Finally, Robin asks about the long-term political outcomes. A slightly cynical view is that, actually, not much will have changed. There is a possibility that this will strengthen the shift towards more concentration in power for the governments. Judging from the long-term consequences of the 2008 crisis, the economic and social effects of the lock-down will be harsh, but again, it is too early to say which direction this will all go.

However, there is one often overlooked aspect. Hopefully, the outbreak and the lock-down will actually result in us feeling more responsibility towards other people, to suffer gladly inconvenience because we actually care to protect those at risk, to go out and help the elderly with shopping, to share toilet paper rolls with those who are unable to go out and shop, to become more united as families, neighbourhoods, and countries. Perhaps in years to come, we will see it as a positive thing.

As usual, if you have comments, please send them to me at info@statisticallyinsignificant.uk

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