Decoding India's COVID R-Factor: Should We Be Worried?

'The intensity of any future third wave should be distinctly less than the intensity we saw in the second wave.'

5 min read

As India's R0, a number that indicates how many people an infected person will pass on the virus to, inches closer to 1, there is some apprehension on how India's COVID graph will play out.

The daily new cases, while on a decline, are not declining at the pace they should. And as daily vaccination rates also slow down, and as cases in Kerala and parts of North East, continue to remain stubbornly high, how worried should we be?

The Quint chats with Dr Gautam Menon, professor of physics and biology at the Ashoka University.

At what stage should we worry about the R value in the pandemic?

Prof Gautam Menon: So right now, across much of India you the have R values a little below one. That’s good sign to tell you that the epidemic is on its down swing in those regions. This is not true across all of India. Kerala still has a R which is a little above one. Parts of North East have R values which are somewhat further way from one.

In general the rule is that if your R is greater than one you number of cases on a day to day basis keep increasing, if less than one, they are decreasing. If they are increasing they signal an incipient leading to potential pandemic / epidemic locally. If they are decreasing it tells you that the epidemic has run its cause on its way down.

Many things can interfere with it for example a new variant can come along which is more transmissible and moves more easily between people. That can drive your R up.

I wouldn’t say this is the only important number. Test positivity is significant. The WHO says that the numbers should be less than 5%. Currently across much of India it should be probably 1.5 to 2% which is a good sign.

So, I think it’s a combination of many factors. If test positivity leads to a large number of cases, and even it doesn’t budge very much from that value, it still is a problem in terms of public health.

But the problem is a lot of this depends upon the testing that you do. If you don’t test, you don’t pick up cases and the gap between the number of cases that you manage to pick up and the number of cases that are out there in the community becomes large. That is what we need to watch out for.


What is happening in Kerala where cases are not going down much despite high vaccination rates?

Prof Gautam Menon: So, Kerala is a mystery. I feel that Kerala was more successful than other states in terms of controlling its cases and its numbers and in terms of controlling its infections. It shut down fairly stringently and it unlocked fairly rigorously. If you look at the sero surveys conducted in Kerala, it was found that about 10% of people had prior infection by 10th of January compared to numbers like 20% plus across all of India on average.

So that suggests to me that overall fewer people on average are infected in Kerala. But on the other hand, there are more people to be infected and that’s a negative and I think that what you’re seeing in the reluctance of the numbers to come down. There’s a background of infection but importantly those numbers are not large enough to cause a serious strain on the health system.

What’s happening in the North-East states that are showing higher number of cases?

Prof Gautam Menon: If you look at the curve, it looks like the epidemic in much of the north eastern states never really came down after the second wave. They came down a little bit and then they began to show an up trend, so maybe this is just the fact that the second wave hasn’t complete its course.

And of course you pointed out the role of vaccination, vaccination is very important. And we need to step up vaccination in those regions where we suspect that there is still a background of large susceptible population yet to be infected.


How concerned should we be in Delhi when we see a rise in cases in Maharashtra?

Prof Gautam Menon: It’s very hard to confine an outbreak in one region because people travel. There are no hard boundaries between states. There are people who travel by air, and a new variant that they figured in Delhi can move to Chennai, or to Hyderabad or to Kolkata within the space of a couple of hours.

Currently, I would not worry too much about Maharashtra. I think this is sort of temporary and whenever you open up you will see a slight rise in cases. Maharashtra and Kerala are recording cases. This does reflect some underlying reality, but given that Maharashtra did experience the brunt of the second wave in a sense that Delta variant really started off in rural areas, and from tier 3 and tier 2 cities in Maharashtra, I would suspect that there is still a fair amount of immunity from prior infection either from the first or the second wave, and that will surely help stem a very steep rise of cases in the future. I would be positive not just about Maharashtra, but about much of India.

What do you make of predictions about the third wave hitting now or in September? Some experts say we might already be in the third wave?

I would not believe any prediction that is several months out, in fact I think that the role of theoretical modelling should be to really look at the short term and give some indication of what might happen, if for example a new variant came out that is say twice more transmissible than the delta variant or the other variants that we’ve seen.

But I will not take a prediction seriously if it says that we have a wave starting on the 15th of September or 15th of October as they are all guesses.

And as I said, much of modelling would suggest that the intensity of any future third wave should be distinctly less than the intensity we saw in the second wave for multiple reasons.

One is that we do know that we have some immunity from the prior infection. We’ve 38% of the eligible population vaccinated with one dose and a smaller fraction with full two doses. We need to step that up.

With a combination of vaccinations, infections and some measure of caution of how we open up, I don’t think you’ll see anything of the sort of the devastation we saw in the second wave.

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