Researchers Responding to COVID-19


Impact of Lockdown on COVID-19 Transmission Dynamics

Study led by Joydev Chattopadhyay of Indian Statistical Institute

In collaboration with Tridip Sardar (Former PhD student, ISI), Dinabandhu Andrews College, Sk Shahid Nadim (PhD student, ISI)

Model Adopted

There are currently very few models for studying the impact of lockdown on COVID-19 transmission dynamics. Based on the development and epidemiological characteristics of COVID-19, a Susceptible Exposed Infected Recovered (SEIR) type model with asymptomatic, and hospitalized or notified population is proposed.


Daily COVID-19 reported cases (Maharashtra, Delhi, Tamil Nadu, and overall India) were considered to estimate the model parameters (


We observe that for Maharashtra, and overall India, the number of symptomatic individual is very low, indicating there is a large number of undetected cases present. On the other hand, the transmission rate id very high, and the transmission variability factor is low, suggesting the existence of potential super spreaders among symptomatic infected.

In Delhi, and Tamil Nadu, there is a large percentage of symptomatic infected cases, and the epidemic curve will reach its peak very quickly.


We suggested 21 days' lockdown will not be effective if it is not extended further. In the extension period constant monitoring is needed to make the lockdown successful. It is also suggested the lockdown should be implemented in a region where there is a large percentage of symptomatic individuals exists. The number of cases and deaths will be reduced substantially if the lockdown is implemented strictly following the Government norms.

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Lockdown Policy and Disease Eradication

Study led by Indranil Mukhopadhyay of Indian Statistical Institute

In collaboration with Sarmistha Das (Research Associate, ISI), researchers from Purulia Medical College, and researchers from All India Institute of Hygiene & Public Health, Kolkata

The Two Key Components of the Study

  1. Objective calculation of the number of lockdown days
  2. Number of people who could be safely quarantined together in cluster

The Findings

  1. For India, ideal lockdown days may be 22-29 days
  2. 43-68 people (CCS) could be quarantined together
  3. Time to extinction of the disease may be 2-3 years
NB: We are currently calculating ideal lockdown phases for States/UTs of India.

The Approach

In this article, we have proposed a mathematical model to answer some of the questions, borrowing the idea from Bartlett's work on Critical Community Size (CCS) in 1957. Our study provides a rationale behind the determination of the lockdown period in different countries going through the catastrophic effect of the pandemic. We have provided country-specific ideal lockdown days that might almost eradicate or weaken this first wave of the pandemic. Our study predicts that a localised lockdown of 22-29 days in India in a community size of a 43-68 people where Covid-19 outbreaks have been reported can help eradicate the diseases in a 2-3-year timeframe.

These mathematical models are designed with available data till April 1. However, we must factor in the fact that this is a new disease and we have little disease-specific knowledge to fall back upon. So the above figures can give an approximate idea.

Take Away Message

The pandemic may cease to exist after country-specific Temporary Eradication of Spread Time (TEST). To our understanding this time frame, TEST, is actually the lockdown period. However, like other epidemics, the disease may recur afterwards in multiple waves. Of course, it may not create any epidemic situation in the later phases, as it is likely to occur locally at different times just like any other epidemic. Even in such situations in future, as soon one infected person is identified, we can implement the local quarantine policy where a group of people, the maximum number being CCS, may stay together in clusters.

So, following lockdown rules strictly is the only way to fight out COVID-19 in absence of specific treatment or vaccine.

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