More food for thought
In announcing the most far-reaching restrictions on personal freedom in the history of our nation, Boris Johnson resolutely followed the scientific advice that he had been given. The advisers to the government seem calm and collected, with a solid consensus among them. In the face of a new viral threat, with numbers of cases surging daily, I’m not sure that any prime minister would have acted very differently.
But I’d like to raise some perspectives that have hardly been aired in the past weeks, and which point to an interpretation of the figures rather different from that which the government is acting on. I’m a recently-retired Professor of Pathology and NHS consultant pathologist, and have spent most of my adult life in healthcare and science – fields which, all too often, are characterised by doubt rather than certainty. There is room for different interpretations of the current data. If some of these other interpretations are correct, or at least nearer to the truth, then conclusions about the actions required will change correspondingly.
The simplest way to judge whether we have an exceptionally lethal disease is to look at the death rates. Are more people dying than we would expect to die anyway in a given week or month? Statistically, we would expect about 51,000 to die in Britain this month. At the time of writing, 422 deaths are linked to Covid-19 — so 0.8 per cent of that expected total. On a global basis, we’d expect 14 million to die over the first three months of the year. The world’s 18,944 coronavirus deaths represent 0.14 per cent of that total. These figures might shoot up but they are, right now, lower than other infectious diseases that we live with (such as flu). Not figures that would, in and of themselves, cause drastic global reactions.
Initial reported figures from China and Italy suggested a death rate of 5 per cent to 15 per cent, similar to Spanish flu. Given that cases were increasing exponentially, this raised the prospect of death rates that no healthcare system in the world would be able to cope with. The need to avoid this scenario is the justification for measures being implemented: the Spanish flu is believed to have infected about one in four of the world’s population between 1918 and 1920, or roughly 500 million people with 50 million deaths. We developed pandemic emergency plans, ready to snap into action in case this happened again.
At the time of writing, the UK’s 422 deaths and 8,077 known cases give an apparent death rate of 5 per cent. This is often cited as a cause for concern, contrasted with the mortality rate of seasonal flu, which is estimated at about 0.1 per cent. But we ought to look very carefully at the data. Are these figures really comparable?
Most of the UK testing has been in hospitals, where there is a high concentration of patients susceptible to the effects of any infection. As anyone who has worked with sick people will know, any testing regime that is based only in hospitals will over-estimate the virulence of an infection. Also, we’re only dealing with those Covid-19 cases that have made people sick enough or worried enough to get tested. There will be many more unaware that they have the virus, with either no symptoms, or mild ones.
Any testing regime that is based only in hospitals will overestimate the virulence of an infection
That’s why, when Britain had 590 diagnosed cases, Sir Patrick Vallance, the government’s chief scientific adviser, suggested that the real figure was probably between 5,000 and 10,000 cases, ten to 20 times higher. If he’s right, the headline death rate due to this virus is likely to be ten to 20 times lower, say 0.25 per cent to 0.5 per cent. That puts the Covid-19 mortality rate in the range associated with infections like flu.
But there’s another, potentially even more serious problem: the way that deaths are recorded. If someone dies of a respiratory infection in the UK, the specific cause of the infection is not usually recorded, unless the illness is a rare ‘notifiable disease’. So the vast majority of respiratory deaths in the UK are recorded as bronchopneumonia, pneumonia, old age or a similar designation. We don’t really test for flu, or other seasonal infections. If the patient has, say, cancer, motor neurone disease or another serious disease, this will be recorded as the cause of death, even if the final illness was a respiratory infection. This means UK certifications normally under-record deaths due to respiratory infections.
Now look at what has happened since the emergence of Covid-19. The list of notifiable diseases has been updated. This list — as well as containing smallpox (which has been extinct for many years) and conditions such as anthrax, brucellosis, plague and rabies (which most UK doctors will never see in their entire careers) — has now been amended to include Covid-19. But not flu. That means every positive test for Covid-19 must be notified, in a way that it just would not be for flu or most other infections.
In the current climate, anyone with a positive test for Covid-19 will certainly be known to clinical staff looking after them: if any of these patients dies, staff will have to record the Covid-19 designation on the death certificate — contrary to usual practice for most infections of this kind. There is a big difference between Covid-19 causing death, and Covid-19 being found in someone who died of other causes. Making Covid-19 notifiable might give the appearance of it causing increasing numbers of deaths, whether this is true or not. It might appear far more of a killer than flu, simply because of the way deaths are recorded.
If we take drastic measures to reduce the incidence of Covid-19, it follows that the deaths will also go down. We risk being convinced that we have averted something that was never really going to be as severe as we feared. This unusual way of reporting Covid-19 deaths explains the clear finding that most of its victims have underlying conditions — and would normally be susceptible to other seasonal viruses, which are virtually never recorded as a specific cause of death.
Let us also consider the Covid-19 graphs, showing an exponential rise in cases — and deaths. They can look alarming. But if we tracked flu or other seasonal viruses in the same way, we would also see an exponential increase. We would also see some countries behind others, and striking fatality rates. The United States Centers for Disease Control, for example, publishes weekly estimates of flu cases. The latest figures show that since September, flu has infected 38 million Americans, hospitalised 390,000 and killed 23,000. This does not cause public alarm because flu is familiar.
The data on Covid-19 differs wildly from country to country. Look at the figures for Italy and Germany. At the time of writing, Italy has 69,176 recorded cases and 6,820 deaths, a rate of 9.9 per cent. Germany has 32,986 cases and 157 deaths, a rate of 0.5 per cent. Do we think that the strain of virus is so different in these nearby countries as to virtually represent different diseases? Or that the populations are so different in their susceptibility to the virus that the death rate can vary more than twentyfold? If not, we ought to suspect systematic error, that the Covid-19 data we are seeing from different countries is not directly comparable.
