Coronavirus outbreak: How lock downs can break the chain of transmission?

PM Narendra Modi, on 24 March, announced a 21-day nationwide lockdown for India. Apart from India, the European Union (EU), the United States, United Kingdom have also announced such lockdowns the contain the spread of COVID-19 virus. World Health Organization (WHO) has already made clear that the vaccine is almost 12-18 months away, even the efforts are underway in full swing. Amidst such a situation, social distancing is pretty much the only intervention available to help individuals stay healthy and to break the chain of transmission. But how exactly does a lockdown work?

A new study by Imperial College London has highlighted the benefits of lockdown. It also explains the mechanism through which a lockdown works. The objective of such lockdowns is to keep reproduction or “R,” below one (R<1) – with each case infecting fewer than one other person, on average. The study suggests that painful as lockdown may be for many of us, it works.

The report suggests two methods in doing so:

• Mitigation, “slowing but not necessarily stopping epidemic spread – reducing peak healthcare demand while protecting those most at risk of severe disease from infection.” This is done by isolating suspected cases and their households, and social distancing the elderly and people at the highest risk of serious illness
• Suppression, or basically, lockdown, which “aims to reverse epidemic growth, reducing case numbers to low levels” by social distancing the entire population “indefinitely” and closing schools and universities.

The study suggests that if social distancing measures were not implemented in US or UK, almost 80% of the population would have got infected. In contrast, isolating confirmed and suspected cases and social distancing the elderly and vulnerable would “reduce peak critical care demand by two-thirds and halve the number of deaths,” notes the report. The report says that to get closer to the goal of R<1, they say, “a combination of case isolation, social distancing of the entire population and either household quarantine or school and university closure are required.”

Since 23 January 2020, the Chinese government locked down Hubei Province, including Wuhan, the city of 11 million where the outbreak started. In some areas, residents were even forced to limit trips to the store or order supplies for delivery. Following the lockdown, cases began to slow. On 19 March, China’s National Health Commission reported no new confirmed infections in Hubei. A very clear impact of lockdown was seen in the Lodi province in Italy. Lodi was closed down on 23 February. On the contrary, another town, Bergamo was closed down on 8 March. As a result, the curve peaked up to more than 2400 cases whereas Lodi witnessed close to 11oo cases.

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