How deadly is the coronavirus? It’s still far from clear

‘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.’