While most countries of the world battle against coronavirus, there is a more conceptual battle raging between different predictive models. Imperial College has predictions for the US and the UK, and has the ear of the Government, but there are other models competing for attention.
The Imperial model is now being cast as having been over-dramatic, and pessimistic, and almost blamed for an unnecessary lockdown, while the Oxford and some other models are seen as more realistic, suggesting that the scare is over-blown, and many people have already caught the virus and developed herd-immunity.
At desperate times like these I have made the ultimate sacrifice, and read the Imperial document again. I know this is not a popular strategy, but I am an occasional contrarian.
Imperial place the dilemma up front: suppression of the epidemic is the best policy, mitigation second best. Stop there. Understand what that means. Strict measures have to be applied quickly, before they appear to be justified. This is what China did, after the false start of castigating the doctors who initially reported the outbreak. China lost valuable time. 7 million left the province before lockdown. Too secretive, too much central control, too unwilling to hear bad news. Then they went into overdrive, locked down Wuhan and then Hubei province. So, from a virus control point of view, they had the central control they needed, in just the right large quantities. Draconian. The firm smack of authoritarian leaders. Effective, and damn the consequences for individual liberties. That is, effective so far, but still at some diminished risk when controls are lifted.
Diminished because quarantine and isolation mean that the wave does not pass, so much as disappears. We are the stepping stones which the virus requires to provide it with new hosts. If we stay at home, or at least very far apart, it can die out. Or almost die out, if widespread testing and contact tracing does not take place.
However, if a country delays in taking those essential early precautions, then they have opened themselves up to infection. The virus is out of its box. All that can be done then is to mitigate the worst effects. Basically, it is inconvenient if everyone gets ill and dies at the same time. Spreading the deaths out a bit helps with arranging home deliveries, and then with coffins, mortuaries, hospital systems and the general functioning of a well-tempered State.
Two fundamental strategies are possible: (a) mitigation, which focuses on slowing but not necessarily stopping epidemic spread –reducing peak healthcare demand while protecting those most at risk of severe disease from infection, and (b) suppression, which aims to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely. Each policy has major challenges. We find that that optimal mitigation policies (combining home isolation of suspect cases, home quarantine of those living in the same household as suspect cases, and social distancing of the elderly and others at most risk of severe disease) might reduce peak healthcare demand by 2/3 and deaths by half. However, the resulting mitigated epidemic would still likely result in hundreds of thousands of deaths and health systems (most notably intensive care units) being overwhelmed many times over. For countries able to achieve it, this leaves suppression as the preferred policy option.
We show that in the UK and US context, suppression will minimally require a combination of social distancing of the entire population, home isolation of cases and household quarantine of their family members. This may need to be supplemented by school and university closures, though it should be recognised that such closures may have negative impacts on health systems due to increased absenteeism.
The major challenge of suppression is that this type of intensive intervention package –or something equivalently effective at reducing transmission –will need to be maintained until a vaccine becomes available (potentially 18 months or more) –given that we predict that transmission will quickly rebound if interventions are relaxed. We show that intermittent social distancing –triggered by trends in disease surveillance –may allow interventions to be relaxed temporarily in relative short time windows, but measures will need to be reintroduced if or when case numbers rebound. Last, while experience in China and now South Korea show that suppression is possible in the short term, it remains to be seen whether it is possible long-term, and whether the social and economic costs of the interventions adopted thus far can be reduced.
This is the dilemma with which countries must cope. Set your stopwatch by late December, and then see what each country did. I suggest the same date is used for all countries, because that is the date at which it was generally clear that there was a new epidemic in Wuhan.
Years ago I was interested in how countries responded to major crises, and talked to Alexander George about the Cuban Missile Crisis. He was kind enough to give me his card, with the request that I contact him, to the surprise of his colleagues, who found he guarded his time very carefully. Naturally, I never did. I think it was he who, when interviewing those close to JFK always asked: What would you have liked to know before the crisis arose?
I suppose the answer regarding the Coronavirus crisis is that world leaders should have known at least as much as Bill Gates in 2015, if not precisely exactly the risks that infection disease specialists had known for at least 20 years: a highly contagious respiratory disease would be very hard to control, and would require very prompt Government restrictions, none of them popular. I used to follow the work of Prof John Oxford, who had warned about these risks for two decades. We seemed to have dodged the bullet several times, and I frankly confess that I had begun to feel that we would muddle through, and not get anything comparable to the Spanish Flu, though it was obvious that the next respiratory disease would come from China: pigs, ducks and Chinese peasants is a species-hopping opportunity viruses find too good to miss.
Anyway, the document introduces the topic thus:
As of 16th March 2020, there have been 164,837 cases and 6,470 deaths confirmed worldwide. Global spread has been rapid, with 146 countries now having reported at least one case.
This is now a quaintly historical document.
As at 31 March 12.00 London time we are at 792,509 total Confirmed Cases, 37,947 deaths.
By the time you read this, that will be out of date, so update here:
or in a different way here:
Imperial say the Spanish Flu is the best comparison, given that this one is highly contagious and there is no vaccination available.
Measures adopted included closing schools, churches, bars and other social venues. Cities in which these interventions were implemented early in the epidemic were successful at reducing case numbers while the interventions remained in place and experienced lower mortality overall1. However, transmission rebounded once controls were lifted.
The documents sets out its assumptions, and the basis on which they have been chosen. That is fine, but it would be good if modellers could agree a standard format for doing so, and summarize everything so that different models can be easily compared.
Their key Table 4 shows what they predicted would happen in the UK given various options of mitigation.
You can check that against the dates to see how close the match is as the numbers keep coming in.
You may feel that you now understand disease modelling pretty well, so why not have a go at testing some hypotheses? Here is a do-it-yourself calculator.
A caution: many of the figures which go into these predictive models have high error terms. Deaths, it would seem, are one of the best things to measure. Not quite. Deaths are occurring mostly in ill elderly people. What is the cause of death? Before December 2019 the death certificate would vary from country to country, but would very probably list the underlying condition: diabetes, high blood pressure, cancer etc where the patient is finally finished off by pneumonia. The pneumonia on its own would have been sufficient as one of the causes of death. There would have been no need to track down the virus involved. Irrelevant. Now, however, there is a test for Covid-19. So, a positive result on the test, and the death of a person, will lead to the view that the death was caused by Covid-19. However, they may have died with it, not of it.
It is far better to look at excess deaths. Every winter there are death rates in excess of the usual summer death rates. Do we have higher rates now? That is not yet clear.
You might also like to read something in support of the very simple hypothesis that if everyone wore masks in crowded public places, transmission would be lower. Much lower.
The coronavirus is testing our intellects and our characters. We have to work out how bad it would be if we continued Life As Usual, and then the steps we could take, balanced for costs and benefits in human terms, to combat it. Test and trace, quarantine the infected, and keep going I will call the Singapore option; some variety of lockdown the Standard option; do little the Swedish option (now strengthened towards the Standard option); and as for the US option, you name it for me.