‘You can't make COVID-19 law-and-order issue, it's about explanation and education’

Dr Murad Banaji, a London-based mathematician with an interest in disease modelling, has been decoding Covid-19 on his Twitter account

Mumbai is currently in the middle of another lockdown and will be till April 30 due to the surge in the number of COVID-19 cases. While the city is also facing a vaccine shortage, the Maharashtra government has been attempting to curb the increase in infections. As both the state and people continue to grapple with the situation, there is no clear solution.

Dr Murad Banaji, a London-based mathematician with an interest in disease modelling has been decoding COVID-19 on his Twitter account (@muradbanaji), catching the attention of many around the world. In a chat with mid-day.com, Banaji, who is a senior lecturer in mathematics at Middlesex University, London, breaks down the complexities of the pandemic with a focus on the current surge in Mumbai.

Here are some excerpts from the interview:

1. What kind of trend do you currently see in the rate of Covid-19 infections in Mumbai? Do you predict another surge?
Mumbai is currently experiencing a very severe Covid-19 surge. We can see this in the huge rise in daily cases, the big rise in test positivity (ratio of total cases to total tests), and the big rise in hospitalisations. Sadly, now the mortality rate is also growing. The hope is that new measures recently put in place will soon bring down daily new cases. But because there is so much active infection in the city right now, even if measures are quite effective, the disease will continue to spread for some time - within families and close communities at least. Daily cases will come down but take time to get down to low levels. This surge has some way to go.

2. Do you have any calculations for how the epidemic can slow down or near its end in Mumbai, especially after the sudden surge?
It's hard to do exact calculations, partly because we don't know exactly how many people have been infected in the city, and how much this protects them from reinfection by whatever variants are currently circulating in the city. But there are things we do know: the disease spreads most easily in crowded spaces, 'especially' if they are indoors and poorly ventilated. Indoor gatherings must be avoided where possible. If an indoor gathering is essential, it should be kept as short as possible and the spaces need to be kept well ventilated. Of course, masks are very important - this includes in outdoors spaces where people are in close contact.

It would be great if vaccination could contribute to slowing the surge. But given current shortages and the slow pace of vaccination, it won't contribute much to controlling spread. But vaccination is still crucial: doing the maximum possible vaccinations of vulnerable groups will reduce severe disease and deaths. Even if it can't slow down the disease very much, it can still save a lot of people from hospitalisation. It is essential that vulnerable people in all parts of the city, including in the slums, can easily get vaccinated - without having to go online or fill out forms. Temporary vaccination centres in different neighbourhoods would help.

3. What is the best possible way right now to stop the infection rate in the city? Does the lockdown system help?
"Lockdown" is not a very helpful word. For one thing, it creates panic. In India, it tends to imply a mixture of measures some of which are helpful and some of which are not. Also, we know well that the previous lockdown didn't manage to effectively slow the epidemic in the slums - it is wrong to force people to stay in their living spaces when these are small, cramped spaces with shared facilities. Disease could well spread faster if you confine people to such spaces. Also, there is no great benefit in shutting outdoor spaces like parks and beaches unless they are getting very crowded.

Most importantly, you can't make COVID-19 into a law and order issue - it's about explanation and education. We need much better public health education about what are risky situations. Gatherings for cultural or religious reasons need to be minimised. Masks need to be worn properly. Non-essential activity needs to stop - e.g., people travelling to work which can be done remotely, or having social visits which can wait. The government needs to support people financially who are in non-essential jobs but still need to work to earn a living.

4. How does Mumbai fare compared to other major cities around the world?
Mumbai's surge is bad, but we are seeing bad surges in almost every major Indian city too. Generally, we know that COVID-19 can spread very fast - in that way Mumbai is not exceptional. But I don't think that many people expected this surge to be so large given how badly Mumbai was already affected during 2020.
Outside of India we've also seen very rapid city epidemics even in cities hit badly before. For example, Manaus, in Brazil was hit very badly by COVID-19 two times. It was a city that people like me were watching. And anyone watching Brazil should have been worrying about what was to come in India. Brazil should have been our warning.

5. Is the rate of infection in 2021 faster than that of 2020?
There are two questions really. Q1) Are daily new infections in the city higher than ever before? Yes, I think so. It's hard to be absolutely certain, because we never know exactly how many infections are being detected in testing, but the data suggests that transmission in the city is faster than ever before. This also means that levels of active infection are very high: the number of people infected right now is perhaps at its highest ever. Q2) Have things got worse very fast - is the 'acceleration' worse than ever before? It is true that things have got bad very fast - but in the early days of the epidemic (March-April, 2020) cases and deaths grew even faster. Still, the acceleration has been very rapid this time too - even if it hasn't quite reached the levels of March-April 2020. And it is this acceleration that make me suspect that we may be seeing new variants circulating in the city.

6. Can you break down the simple terms the average citizen must know in order to be educated about the technicalities of Covid-19? For example: What is the meaning of R0, herd immunity, among others.
R0 is the average number of new people that one infected person infects in the early days of the epidemic - i.e., when there are no measures to slow spread. RO = 3 would mean that one person typically infects three more. But this is an average - many people will not infect anyone else, or at most one or two people; a few people will infect tens or hundreds of people. R0 depends both on the virus and on the environment - crowding, population density, transportation, can all affect R0.

R(t) is the same thing - the average number of new people that one infected person infects - but at any given moment in time. For example, recently I estimate that R(t) in Mumbai has been around 1.5 to 1.7. That means that two infected people cause roughly three new infections on average. There are a number of assumptions in such estimates, so they come with uncertainty.

'Herd immunity' is a complicated, and much misunderstood and misused, concept. The very rough idea of herd immunity is that when a sufficient number of people have become immune to a disease then the existing outbreak starts to wind down - R(t) comes below 1, and daily new infections start to decrease, even if there are no measures to slow the spread of the disease. And if disease has already faded away, and you have herd immunity, then major new outbreaks shouldn't occur. BUT there are a lot of assumptions behind these expectations, and many of them don't necessarily hold in the real world. In real world situations you can have outbreaks after herd immunity is reached. And if you have new variants coming into play, then the whole notion of herd immunity needs to be thought through again - especially when immunity against one variant isn't so effective against another.

7. What are the common misconceptions about the spread of the disease right now? Can you debunk them for us mathematically?
I'll focus on one thing: people are hoping that deaths will be fewer this time around, even if disease spreads widely. I think it is always good to hope, but not correct to assume it will be so. It is good to think like an optimist, but act like a pessimist. We know that some variants are more lethal - more likely to cause severe disease or death. In some parts of the country there is evidence that more lethal variants are circulating. And even without a more lethal variant, if you have a variant which spreads very easily - which is more "transmissible" - then you can have a lot of deaths simply because a lot of people get infected.

In cities like Mumbai, the hope is that because a lot of people have been infected already, the impact will be less: even if they get infected again, the disease will generally be less severe. There is some evidence pointing this way, and I'm certainly hoping this. I'm also hoping that more and more vaccination in vulnerable groups - specifically the elderly and people with comorbidities - will reduce deaths in the city. But seeing the rapid rise in hospitalisations, I'm worried the total level of deaths in this wave will end up being high, despite these factors.

8. Is the rate of infection from a new strain higher than that of the old strain?
We don't know what variants are circulating in Mumbai - there just isn't the level of genome sequencing required to get a clear picture. So, a lot of talk about variants is educated guesswork at the moment. In general, more transmissible variants eventually come to dominate - they have a competitive advantage over ones which spread more slowly. So, it could be that a more transmissible variant is circulating in the city. A variant which can reinfect people infected earlier by another variant also has an advantage. Such an "immune escape" variant could be circulating - this would result in more reinfections than expected. So, alongside vaccination and testing, sequencing is urgently needed - we need to find out exactly which variants are circulating in Mumbai (and India more generally). Without a major increase in sequencing, and regular release of the data, you have a lot of speculation. And, of course, we want policy to be based on data, not speculation.