A Layman’s Study of the Covid-19 Pandemic
In trying to make sense of the Covid-19 pandemic one has to wade through on the one hand a mass of technical information available online, each one on a very specific segment of the situation, and on the other hand a deluge of fear, innuendo and false information circulating on social media. This is my attempt to cut through the fog. Being a layman, you must recognise my lack of expertise and take what I say here with a pinch of salt. The goal is to offer some clarity rather than an unimpeachable foundation for action.
Epidemiologists use a number to measure the degree to which a virus in infectious. This number, known as ‘R-0’ (typically pronounced ‘r-nought’) defines the number of people who are likely to be infected by a person who has already caught the virus. If R-0 is less than one, it means that spread of the virus is on the decline. If R-0 is greater than one, it means spread of the virus is on the increase.
At this moment, it is difficult to pin down a single value for R-0 of Covid-19: not only does the rate of spread vary across different regions, but we are not even sure if the numbers are accurately reflected given the wide variance in the extent of testing across countries. In some areas, R-0 has been measured as low as 1.5. At the height of the infection in China, R-0 was measured as high as 6 in the hot spots. It is safe to assume that the global average of R-0 for Covid-19 is currently greater than 2. This means that its spread is exponential.
Given that a vast majority of the population has either not studied maths or has forgotten whatever maths that was studied in school, there is low popular understanding of what exponential growth is. There are broadly two kinds of progression: arithmetic and geometric. In an arithmetic progression the rate of change is constant, as in the series (2,4,6,8,10……), and the difference between one number in the series and next is the addition or subtraction of a constant number. In a geometric progression, the rate of change also changes, as in the series (2,4,8,16,32…….), and the difference between one number and the next is the multiplication by a constant number, also known as an exponent. In an arithmetic progression, if you are currently seeing a slow rate of change, that means you can rest assured that this slow rate will continue into the future. In a geometric progression, the multiplication by the exponent keeps getting applied to a larger and larger number, and this exponential rate of change escalates rapidly. If you are currently seeing a slow rate of change, there is no common-sense methodology by which you can sense what the rate of change will be in the future; this can only be modelled mathematically.
An understanding of exponential growth can be had through a thought experiment. Imagine a pond on the surface of which is a single lily pad. This lily pad has the capacity to reproduce itself in a 24-hour cycle. This means that if on the first day there is only one lily pad, on the second day there will be two, four on the third day, eight on the fourth day, and so on. You are given the information that the surface of the pond will be completely covered by lily pads in 48 days and asked on which day will 50% of the pond be covered. Most people have an intuitive reaction that places their guess fairly close to the mid-point of 24 days. But actually 50% coverage is achieved only on the 47th day, the day before the pond is completely covered. Moreover, the coverage of the pond by lily pads exceeds 1% of total pond area only on the 42nd day.
One cannot draw a strict equivalence between this lily pad simulation and the spread of the virus, because in the case of the virus, some people stop spreading the infection either because they recover or because they die. But it does give a sense of how a lack of understanding of exponential progression can create a false complacency in the early days of the progression.
Global spread of the virus goes through three stages.
1. Imported: A person contracts the virus because they have travelled to an area where the virus is rampant, caught the infection, and brought it to an area where the virus is not yet rampant.
2. Local: A person gets infected through contact with someone who has imported the virus.
3. Community: The spread of the virus is through such a multiplicity of sources that there is no way of establishing the source by which a person has become infected. Once the ‘Community’ stage is reached, the spread of the virus is likely to be exponential.
Given there is no vaccine or medication currently available to combat the virus, there are only three available strategies to fight the virus: suppression, mitigation and containment. Suppression is by placing restrictions on the movement of people through lockdowns and/or curfews. Mitigation is less strict and depends on voluntary cooperation. It depends on behaviours that establish social distancing through keeping distance from others, staying at home except for absolutely essential survival needs, not touching others, etc. Mitigation also involves sanitation practices such as frequent and thorough washing of hands, not touching eyes, nose and mouth, and self-quarantine within the home by people who are either infected or have recently travelled. And finally, there is containment, where through extensive testing, infected people are traced, contacted, isolated and treated so that they do not mingle with the general population and spread the infection. Testing is important, as asymptomatic carriers can also spread the infection.
The good news is that China, the original source and hot spot of the virus, has been able to bring things under relative control with a combination of strict enforcement of both suppression and mitigation. In addition, there was a quick ramping up of both testing and healthcare infrastructure. As can be seen from the graph above, the cumulative total of cases has flattened out, and the reporting of new cases has dropped to very low levels. So effective strategies are possible.
The problem has shifted to the rest of the world, with most countries being slow off the blocks, and are now grappling with a virus spread that has reached the ‘community’ stage. China had also reached the community stage in many areas, was able to overcome it, and we must learn from this and act accordingly.
Countries in the developing world (such as India and many African countries) will have to immediately implement serious suppression measures before widespread community transmission becomes disastrous given a context of inadequate healthcare infrastructure, crowded living in urban areas, and a high percentage of population lacking access to water and sanitation required for mitigation measures such as washing hands. Suppression also becomes a way of buying time in order for a poorly organised health sector to ramp up the capacity for containment. It will be a complex balancing act, because the number of poor people living on the edge of survival could result in deaths from starvation in an extended period of suppression. We will not be able to mitigate Covid-19 if governments are lackadaisical in implementing suppression measures or are not sufficiently rigorous and publicly transparent on measures to manage and ramp up testing and healthcare infrastructure. We will not be able to mitigate Covid-19 if we, the general public, fail to take this seriously and offer our utmost cooperation in suppression and mitigation measures. We are all in this together.
