Coronavirus: awaiting the cavalry

01/04/2020

The government needed two goes at publishing the Covid-19 figures yesterday. When they first came out, there had been 25,150 cases (up 3,009 from 22,141) and 1,651 deaths (up 367 from 1,284).

No sooner had they been absorbed, though, than the figure for deaths rose to 1,789 suggesting a truly massive hike in the day-on-day figure of over 500. But, almost in the manner of Winston Smith re-writing The Times in 1984, the day before's figures for deaths jumped to 1,408, producing a more modest but nonetheless considerable increase of 381.

To give some indication of the scale of this jump, three weeks ago, Mrs EUReferendum and I were looking forward to a visit from our granddaughter, coming down from Scotland to stay with us for a few days. Watching the daily Covid-19 figures mount, I suggested that, if the cases topped 1,000 by the weekend, we would call the visit off.

As it turned out, the figure reached 1,061 by the Saturday, at which time 21 deaths had been recorded. From that point, we went into our own personal lockdown, which was just as well.

By now we have seen cases multiply 25-fold, and while the official death toll is short of two thousand, there are those who argue that about 25 percent more people have died, putting the number at well over the two-thousand mark.

Nevertheless, according to Public Health England, the average number of deaths in England for the last five flu seasons, 2014/15 to 2018/19, was 17,000 deaths annually. This ranged from 1,692 deaths last season, 2018/19, to 28,330 deaths in 2014/15.

On the face of it, we have a long way to go before we match the 2014/15 figure, but that was particularly bad as the main strain of influenza mutated after the annual vaccine had been prepared, rendering the protection of very limited value.

However, given the current rate of increase of Covid-19 deaths, doubling every four days, the death toll for this epidemic could exceed the 2014/15 flu figure in just over two weeks, compressing the mortality into a brief six-week period, compared with the flu season which lasts four to five months, with deaths peaking over the winter months of December to February.

In terms of control, the principal difference between Covid-19 and winter flu is that the latter is constrained by an annual vaccination programme and, given an effective vaccine, the death rate can be held to relatively low levels.

Without such an aid, Covid-19 might be expected to increase exponentially, infecting up to 80 percent of the population, with a case fatality rate in the order of one percent. It was this projection, with a potential case load of 50 million that gave rise to an estimated death toll of 500,000.

What is not fully appreciated though, is that if coronavirus was left to spread freely in the population, from the current level of two thousand deaths, the half-million deaths would be reached after just nine doubling cycles – in just over five weeks' time.

That is the nature of an exponential growth rate where, in a population with no natural immunity, we would see half a million dead within the space of just over two months. There is not a health system in the world that could cope with that burden. Long before the final death toll was reached, the NHS would have collapsed.

In real life, however, epidemics don't work that way. As the numbers falling ill increase, the incidence of infection slows, with the graph taking on the profile of the classic bell-shaped curve. Nonetheless, in theory, this might extend the epidemic by a few weeks, so we could still see a grotesque number of deaths compressed into a period that would swamp the health service.

And yet, even that isn't going to happen. A very good point made by the BMJ yesterday is that, while there is one epidemic in the UK, there are multiple outbreaks, each with their own unique profiles. At the moment, the largest of these is in London, and there is another hotspot in the West Midlands.

Given unconstrained growth, we can expect the outbreaks to radiate out from London, to the west and north – rather like the Italian experience where the epicentre is moving south. Over a period therefore, we can expect a series of spikes in incidence and mortality, as the disease spreads.

This gives a longer period with which to cope with the epidemic but, without specific controls geared to this specific disease, there would be no overall impact on the number of dead. Rather, the deaths would be spread over a longer period.

You can play about with the statistics, and come up with different projections – with or without the spurious authenticity of calling them computer models – but these will have no effect on the overall dynamics of this outbreak.

Thus when confronted with a novel virus, giving rise to acute respiratory disease, in the absence of a vaccine, there are only very limited control options. The first – as favoured by the WHO – is to carry out an aggressive testing programme to detect cases, combined with equally aggressive contact tracing and testing, to remove the infection from the community.

The other main option, applicable where the community spread is uncontained, is to impose a widespread lockdown, distancing the population from the sources of infection in the hope that the epidemic will slow down sufficiently to allow the health services to deal with the onslaught of cases.

But, in fact, it now transpires that the UK government has gone for neither of those options. The clue to this came with last weekend's article which recorded the failure of a pandemic test run carried out three years ago, under the title "Exercise Cygnus".

What emerged from the article is that, even though the system failed, no amendments were made to the strategic roadmap for a future pandemic, with the last update having been carried out in 2014. The actual working model for the current Covid-19 epidemic, therefore, is the Pandemic Influenza Response Plan, augmented by the Pandemic Influenza Strategic Framework, both published by Public Health England in August 2014.

And in those pages is the previously "opaque" reason why Public Health England so precipitously abandoned the "test and trace" programme, an action which has attracted so much criticism.

The point emerges from the plan that the savagely diminished field epidemiology service was never intended to carry out this programme. Its function was merely to monitor the emerging epidemic, looking for "evidence" of sustained community transmission.

This would be undertaken during the first two phases of the plan, labelled "detection" and "assessment", following which the field service was effectively stood down, while the plan moved to the "treatment" phase, in preparation for "targeted vaccinations" – all based on the assumption that a vaccine would be available 5-6 months after the decision to order it had been given.

With that, the plan moves into the "escalation" phase, amounting to "surge management" of cases by the NHS, which includes "prioritisation and triage of service delivery with aim to maintain essential services". Also introduced are "resilience measures, encompassing robust contingency plans" and then, in the ultimate statement of complacency, Public Health England considers "de-escalation" of its response "if the situation is judged to have improved sufficiently".

This then leads to a "recovery" phase, the end point where we are supposed happily to settle down to the "normalisation of services" and "perhaps to a new definition of what constitutes normal service". And with that, we get "restoration of business as usual services", including "an element of catching-up with activity that may have been scaled-down as part of the pandemic response".

Such a happy outcome is, however, entirely dependent on the development and administration of an effective vaccine, without which there is neither hope nor intention of controlling the epidemic. Stuck as we are in the "escalation" phase, the plan is to hold the fort long enough for the cavalry to come galloping over the hill.

And, seriously, that is what the government is doing.