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View: Beyond the lockdown, to reduce deaths prevent the clusters

In India with the country in lockdown, we only are made aware of few clusters, namely, in Nizamuddin, Chennai vegetable market, Nanded pilgrimage and Mumbai slums. Moving forward, the formation of clusters will define the course of the epidemic in India.

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Last Updated: May 29, 2020, 05.24 PM IST
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Clusters are formed as a result of social obligation, residential settings or work settings.
By Daisy John and Giridhara R Babu

In the ongoing COVID -19 crisis, it is time India does some smart planning in addition to the hard work. The evidence available regarding how the disease spreads is also fast evolving. It is now established that infection can spread through super spreading events, suggesting that few persons spread the disease more, and that not all diagnosed cases lead to secondary transmission.

This individual-level variation can be partly explained by emerging evidence that suggests only symptomatic are spreading the disease faster compared to others. Instead of chasing everyone tested positive, the public health efforts will have to identify these symptomatic super spreaders, which can result in almost 80% of the cases as a result of the secondary transmission.

While presenting the evidence for this, Dr Eric Topo, physician-scientist, ascribed this to the Pareto principle, roughly 80% of the infections resulting from 20% of the people. So, tracking symptomatic and preventing super-spreading events will offer us an immense advantage in reducing mortality.

However, the symptoms should be expanded as done recently by CDC-US and include loss of smell/taste, chills, weakness/muscle pain in addition to the traditional symptoms of flu. We should also identify all symptomatic by improving surveillance. The case definition should be expanded so persons with moderate symptoms are detected to prevent them from spreading to others.

Second, while most epidemiologic models considered Ro, which indicates how many people get infected by one infected person, not one such model has provided estimates so far showing the effect of clusters. Recent evidence suggests that the dispersion factor is as much or even more critical than Ro. This value describes how much disease clusters, with lower values indicate that disease spreads from a smaller number of people. There might be some clusters that have the potential to spread to a larger number of people. Identification of such clusters is the key. This is thought to be the reason why the infection emerged in China did not take-off around the world immediately after it emerged in China. This is also corroborated by evidence in France regarding how the emergence of new cases occurred.

In India with the country in lockdown, we only are made aware of few clusters, namely, in Nizamuddin, Chennai vegetable market, Nanded pilgrimage and Mumbai slums. Moving forward, the formation of clusters will define the course of the epidemic in India. Clusters are formed as a result of social obligation, residential settings or work settings. The cluster formation and its impact on Covid-19 spread depends on individual characteristics, legal enforcements, how some people might shed more virus and for a longer time, etc. While most of it is not known, what we know clearly is that the virus spreads much more in closed space.

Avoiding clusters will be useful in containing the disease; the key clusters that can trigger are the super spreading events. Generally, there is a higher transmission risk in indoor settings, wherever more people in closed spaces are present for a longer time. The implications of these are manifold beyond lifting the restrictions of lockdown. In a work environment, time spent inside closed rooms with many people should be avoided, and if inevitable, the distancing of 1.5 meters is needed from everyone. For most people, work from home has to be extended for time beyond lockdown. Wherever applicable, people should be asked to continue working from home. Densely populated areas need unique management with stricter mandatory use of masks, and even a small gathering should be banned in such areas.

Japan is a shining example of implementing this strategy. The country mounted a successful response by managing prevention through the management of super-spreader venues and the 3 C's- closed spaces, crowds, and close-contact settings. Taking a cue from Japan, we can prevent a further surge in cases by enforcing public health measures, enhance surveillance, testing, and tracing measures. Japan simply stopped any gathering with more than two people anywhere.

With the exceptions of healthcare institutions, we need to prevent the formation of crowds in religious congregations, old age homes, any co-habiting settings such as centres for disabled, schools, marathons, sports events, bars, shopping centres and conferences. All the available cut-offs for classifying large gatherings are arbitrary; China uses 100 as cut off, CDC,US uses more than 250 people. We need to have Indian criteria to prevent clusters throughout the country.

In a high-risk population, CDC states that even gathering of more than ten members is risky. Even when the lockdown is lifted, these measures need postponement of any gatherings planned already, including religious institutions.

Daisy John is a research associate, and Giridhara R Babu is Professor and Head, Lifecourse epidemiology at IIPH, PHFI, Bengaluru. Dr Giridhara is also a member of ICMR's research task force on Epidemiology and Surveillance and Karnataka state’s Technical Advisory Committee for managing covid19.
(Disclaimer: The opinions expressed in this column are that of the writer. The facts and opinions expressed here do not reflect the views of www.economictimes.com.)
(Catch all the Business News, Breaking News Events and Latest News Updates on The Economic Times.)

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