Second wave

Bad news came in over the weekend. Cases are up in Mumbai, and in several smaller towns. Kerala, which had beaten back the pandemic in its early days, has been going through enormous pains in recent weeks. This week, overall, cases are up in India by about a third. We seem to be at the beginning of a second wave. Friends around Mumbai have been discussing the inevitability of such a thing ever since the local trains were opened to the general public. I have been playing the devil’s advocate (what an appropriate phrase at this time) with the argument that if livelihoods are to be safeguarded, we have no choice but to let people move around. An increase of cases today inevitably leads to the conclusion that the policy changes made two or three weeks ago are at the root of the problem. Governments agree, and sometimes have gone the whole hog again, imposing full lockdowns in some towns.

My early training predisposes me to seek answers in an engineering discipline that is called Systems Design and Control Theory. One of the things that we learnt was that you could try to control a system by using its output to influence its input. This is called feedback. There is a theorem which says that feedback with delays leads to oscillations. Every teenager who has tried to form a rock band knows about the screech of feedback which badly placed mics and speakers can lead to. Others can more easily relate to the frustrating experience of making sure that the water in the shower is a comfortable temperature as an experience of oscillations due to delayed feedback.

Why should this lead to second and third waves of epidemics? The argument goes something like this. When it becomes clear that there is an epidemic, governments put various restrictions in place. But these are temporary, and when the number of cases decreases they are removed. Clearly there is a feedback. The delay comes from two sources: it takes time to realize that there is a consistent rise (or fall) in the number of cases, and it takes time for committees to make decisions.

Fortunately, the theorem assures us that we are not doomed to be tossed about forever by waves of the pandemic. If there is friction in the system then that damps out the successive waves. Where does this friction come from? One is the brutal calculus that the most susceptible are the earliest victims of the epidemic, so successive waves of disease, eventually, find better prepared immune systems. The second source is our personal learning and initiative. When we realize that there is danger, we personally take precautions. And we learn what are the most important, and best, measures. The third is the most enlightened reason of all: medical practice evolves, so that treatments and vaccines become available.

Human behaviour is unpredictable. There are no theorems which guarantee how I will act. Still, when studying a large enough body of people, there are general principles which seem to govern how such collections will respond to circumstances. There are limits to such predictions. Different countries, even different cities, have had a their second and third waves of COVID-19 at different times.

There are just three simple things to remember about COVID-19: mask up, keep your distance when possible, and do not gather with many others.

By I. J. Khanewala

I travel on work. When that gets too tiring then I relax by travelling for holidays. The holidays are pretty hectic, so I need to unwind by getting back home. But that means work.


  1. The second wave is a little unexpected in India given the vast number of unreported and asymptomatic infections that are assumed to be gradually building up to herd immunity. A serosurvey in Delhi indicated a 50-60% infection rate and another in Punjab indicated that the number of asymptomatic infections was as high as 83%. Even after allowing for statistical anomalies, most studies did indicate that covid was much more widespread across the country than govt. figures show. Still, this is a worrying trend and I hope the ICMR and other agencies are looking to discount the arrival of a new variant to the scene.

    Liked by 1 person

    1. Newspapers treat all serosurveys as comparable. But they use different test kits, with different false positive and negative rates. The Delhi survey also revealed huge variation from one locality to another in the positivity rates.

      Liked by 1 person

      1. True. Still, within the margins of error, we see a substantial proportion of the Indian population seemingly having had the infection without symptoms so a second wave shouldn’t have arrived. This needs a lot more study but I wonder if our administration is up to the task…

        Liked by 1 person

  2. There is such a disconnect here in the USA between the stark numbers of death and infection and the general low tolerance for restrictions. I just don’t understand it when these 3 simple rules could really mitigate the spread of the disease. I’m at a loss to explain it.

    Liked by 1 person

    1. Everywhere actually. In some ways it seems like human nature to relax when the going is good, and go back to precautions only when it is clear that it is needed. Different people may differ on when it is needed, I suppose.

      Liked by 1 person

  3. I’m sorry to hear you appear to be starting a second wave. We are just coming out of ours now in the UK. The good news is, the vaccines seem to be making a huge difference. A study in Scotland, published just this morning, found that they reduce hospitalisations among the over 80 year olds by 81%, and across the whole population the average reduction is in the high 80-90% area. And that’s just with the first dose! It’s excellent news but the challenge is firstly to ensure high vaccine take-up (we have some vaccine sceptics here and fake information circulating) and secondly for those developing the vaccines to stay on top of any mutations in the virus. But we will get there!

    Liked by 1 person

  4. Interestingly I.J. I just read this week that it seemed India was reaching herd immunity as there was no other way to explain the lower number of cases. It seems the news was lagging vs the current increase in cases. This thing is so insidious, who knows what stage any place is at any given time. I agree, follow the recommendations and take precautions like masks and social distancing no matter what the current rate of infection is. It’s the only real safe option.

    Liked by 1 person

    1. The statements about herd immunity seem to have been based on relatively small samples of people. And it seems that previous exposure to other coronaviruses can affect the results of these tests. So, we really know little.


  5. I’m sorry to read about the bad news in your country. The Prime Minister of Malta stated at the beginning of the pandemic that waves only exist in the sea. Now we have experienced more waves of pandemics. Despite mandatory mouth protection, social distancing, no gatherings, closed bars etc.. Wonder how long will this last and why not everyone follows these simple rules. We all long to return to normal, if ever.

    Liked by 1 person

  6. It was very interesting to read about it from an engineer’s viewpoint, and I was particularly struck by the concepts of feedback and oscillations.
    I wonder if variants are playing a part. My nephew, a doctor, noticed a sharp increase among his patients at one point but that these same people seemed to have milder symptoms. This observation was made long before the press started talking about mutations and variants.

    Liked by 1 person

  7. Thank you very much for this insightful post! It’s been very difficult for me hearing the news of what is happening in India, especially as I am in Australia which hasn’t witnessed the widespread impacts of the virus. I recently posted an article on my blog about the recent outbreak in India and what we can do to support worldwide. If you have time, it would be great if you could check out my post and let me know your thoughts! Thank you and wishing you all the best 🙂

    Liked by 1 person

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