The new virus is a leveler and a game changer, says S.Ananthanarayanan.
It is not correct to say COVID-19 has grabbed centre stage. COVID-19 is the only player in the cast and the whole world has become its stage.
Exponential growth, herd immunity, extending the lockdown, relaxing the lockdown - there are many and differing ideas, strategies and visions that are doing the rounds. Europe and the US have got it bad, our numbers appear to be better, but the jury is out on how India will weather the storm.
There is a section that stresses the speed at which COVID-19 is able to spread. Exponential growth is indeed explosive. High school math can show that one paisa, if it doubles every day, in 30 days would grow to 230, which is Rs 10.74 million. So we know what to choose if we are offered either a lakh or Rupees every day for 30 days, or that fecund single paisa.
The example, however, is unfair to COVID-19. First, the infection does not double every day. Still, based on the growth factor of 2.6, which is given out, an expert in disease dynamics from Princeton said that there would be millions of patients in India in less than four months. This mechanical extrapolation however, may not be valid, as the factor of 2.6 applies to an infected person who surrounded by susceptible persons and without precautions in place. When steps to limit transmission are taken, the factor is much lower and there are prospects of blocking the spread of infection.
A major factor in slows the spread of infections is that persons who are immune after infection (or have been vaccinated) become barriers between infective persons and susceptible persons. As the acquired immunity or vaccination level increases, the rise in infective persons slows, and finally stops. And when infective persons stop being infective, the virus cannot survive, it is eradicated.
This is the phenomenon of ‘herd immunity’, a term used while describing the spread of viral diseases in sheep, cattle, rabies in some animals in the wild, etc. In the 1930s, it was recognized that the spread of measles reversed when sufficient numbers were affected. When this happens, or to what degree the infection needs to spread for herd immunity to set in, depends on the infectivity of the virus. Infectivity is how many new infections each infective individual causes, on the average. This number is denoted as R0 (R naught). Pc, the critical percentage of the population that needs to be immune for herd immunity to set in, can then be worked out with the formula, Pc = 1 - 1/R0. We can see that if R0, or the infectivity is low, ie, one person infects just a little more than one other, Pc is a small fraction. But with high infectivity, Pc can be high. If each person infects 10 other persons, for instance, Pc = 1 – 1/10 = 0.9, or 90%.
In the case of COVID-19, with R0 = 2.6, Pc works out to 0.61. This means 61% of the population needs to be infected for herd immunity to set in. This is clearly too high a number to consider. Currently, about 25 lakh persons, or 0.03 % of the world population of 8 billion are infected. We are obviously very far from herd immunity, and the cost, with even low, fractional mortality, is not acceptable. And the world’s medical facilities would not be able to cope.
There are, however, two reasons why we need not wait for 61% of the world’s population to be infected. The first reason is that R0 is 2.6 only when an infected person is surrounded by persons with no immunity, and she is, in principle, in communication with all of them. This would be true in the early stages, but the effective infectivity reduces as more persons are infected or become immune. Although we need to reach 61% for the spread to stop, the stop is not abrupt, the spread begins to slow down as soon as person No. 2 is infected.
The second reason is that the whole world has now put barriers in the way of the virus, by isolating infected persons, using masks and washing with soap, lockdown of whole cities, to reduce occasions where the virus can cross from person to person. The value of R0 is hence much lower and the speed with which numbers are increasing is slowing in many places. When measures are able to slow the spread, there is time for a vaccine to be developed. And once there is a vaccine, each protected person becomes a barrier to the spread.
The next question is how long we need the lockdown. In India, it was ordered for three weeks. As effects are not apparent, it has been extended. The situation is not expected to be much different, two weeks later, and the reasoning is questioned. Unless the virus is eradicated, it is argued, there cannot be a case to relax the lockdown.
The answer to this is that a lockdown is an extreme measure, it could be called a desperate move get a hold on a runaway situation. In the early stages, lockdown mainly keeps healthy people away from other healthy people. In the late stage, it keeps infected people away from other infected people. More to the point would be to detect where there is infection and see that it does not spread. This would call for massive testing and contact tracing –steps that have been taken, often considered less extensively than desired, in India. But if the scale of the infection becomes known, we may find that the cost of the complete lockdown is not justified. The testing that is now done in India, incidentally, throws up 4.4% of positives. This is against two-digit and higher percentages that are found elsewhere.
We need to recognize that the world is now highly connected – there is almost no pocket that can be considered self-sufficient. A gated society in a metropolis can manage lockdown for a month and may believe it can tolerate more. But supplies must come and if something breaks down, a repairperson must come in from outside. A city may consider itself working well without imports, but most machinery will soon need spares, or hospitals the supplies that the city does not have!
And then, there are sections of society that states cannot support for long. These sections would break the lockdown, “to choose between COVID and starvation,” somebody said. The response was that when they choose COVID, it is not only their choice, it is the choice for everybody. But this apart, all sections of society play a role, which only an economy in motion can sustain.
The answer seems to be that we keep sensible, but educated, responsible and disciplined social distance, hygiene and alertness, simplicity and sustainability, and expect to stay like this for many months, maybe a few years.
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