Abstract
“‘Girl number 20’, said Mr Gradgrind, squarely pointing with his square forefinger, ‘I don’t know that girl. Who is that girl?’. ‘Sissy Jupe, sir,’ explained number twenty, blushing, standing up and curtsying. ‘Sissy is not a name,’ said Mr Gradgrind. ‘Don’t call yourself Sissy. Call yourself Cecilia’”.
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This move, which was by no means uncontested, was intended to galvanise the international community into concerted action to prevent a global threat from becoming a disastrous reality. It would be a further six weeks, on 11 March, by which time there were more than 118,000 cases in 114 countries with 4291 COVID deaths, before the Director General of WHO was able to declare that this was now a pandemic.
Epidemiology, as the underpinning of public health through the application of both quantitative and qualitative methods to ‘the study of that which is upon the people’ (epi = around; demos = the people; ology = the study.(gk)), has, at its heart, the goal of ascertaining reliably what, if anything, is going on that affects public health. From such understanding, and through robust case definition in time, place and person, comes the basis for effective intervention.
With a novel infectious disease such as the Corona virus causing COVID, clarity of definition is of the essence. What we have learned over the past two years has been that reliable definitions of ‘outbreak’, ‘epidemic’, ‘pandemic’ and more recently ‘endemic’ have been elusive and that such elusiveness has affected both professionals and lay commentators alike.
So to cut to the chase:
The term outbreak as applied to an infectious disease should be used when more than one case occurs that can be pinned down in time and place as connected to an initial case where there are sound grounds for assuming a causative link. An epidemic is the term used to describe the widespread occurrence of an infectious disease in a defined population or geographical area. A pandemic as defined by WHO is reserved for use when an epidemic assumes the characteristics of exponential growth in which the spread of infection transcends country and population to assume truly global form affecting a significant proportion of the world’s population.
These three terms together encompass the dynamic of a changed situation from the status quo ante in which human and animal populations live in habitats in some kind of balance formed by the classical public health concepts of agent, host and environment.
It is when disturbances occur within these habitats, through biological mutation; population movements involving in the present time the impacts of globalisation and rapid urbanisation; or environmental rupture or catastrophe, that a natural state of endemic co-existence may give way to outbreaks and their escalation to something much worse.
In recent times these conditions can be seen to have applied to a range of novel pathogens including HIV/AIDS, Bovine Spongeiform Encephalitis, Hong Kong Bird Flu, SARS, Swine Flu, Ebola and now COVID-19. In contrast to the taxonomies implicit in the application of the terms ‘outbreak’, ‘epidemic’ and ‘pandemic’ as technical descriptors to inform practical interventions at the appropriate level, the declaration of a state of ‘Public Health Emergency of International Concern’ (PHEIC) falls into a separate category. As such it represents an effort by the WHO as one of the family of United Nations organisations striving to maintain a rules-based system of global governance in search of global stability. It is subject to all the same strengths as its sister organisations in its ability to galvanise international collaboration of those of goodwill but at the same time the weaknesses of trying to herd the cats of widely varying national political ideologies and rivalries.
In the same way that WHO struggled to make the declaration of a PHEIC stick in the early days of the pandemic, the use of the term ‘endemic’ to describe the latest phase has become a victim of a political battle for the narrative. This battle is between those who wish to declare the pandemic over, the battle won, the normal economy able to resume as ‘business as usual’, and those pragmatists who recognise that the return to a steady state of endemicity in which infection levels by this novel virus recede into the background of daily life is not so simple.
Still hanging out in the shadows is the contaminated belief in a spurious ‘herd immunity’ which must surely be as elusive as Mr Gradgrind’s wish to control the world through his rigid world view as so richly captured in Charles Dicken’s ‘Hard Times’: (Gradgrind to Sissy Jupe) … ‘Very well then … Give me your definition of a horse.’ (Sissy Jupe thrown into the greatest alarm by this demand) ‘Girl number twenty unable to define a horse! … girl number twenty possessed of no facts, in reference to one of the commonest animals’ … ‘Bitzer,’ said Thomas Gradgrind. ‘Your definition of a horse.’ ‘quadruped. Graminivorous. Forty teeth, namely twenty-four grinders, four eye-teeth, and twelve incisive. Sheds coat in the spring. In marshy countries, sheds hoofs too. Hoofshard but requiring to be shod with iron. Age known by marks in mouth.’… ‘Now girl number twenty,’ said Mr Gradgrind, ‘you know what a horse is.’