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Explained: How do physical distancing measures contain coronavirus?

Studies in the UK and on China provide some insights on the extent to which social distancing can be effective in controlling COVID-19.

Coronavirus numbers explained: Why Tamil Nadu is latest cause for worry There is the question about how long should social distancing measures be enforced, and the factors that governments should consider when deciding to lift them. (Express photo: Partha Paul)

Governments across the world have adopted social distancing measures in the forms of lockdowns and curfews in a bid to contain the coronavirus outbreak. Given China’s example, the country where the outbreak first emerged, there is some evidence that lockdowns may be effective, but it is not exactly clear how much these measures control the spread of the infection or “flatten the curve”.

Further, there is the question about how long should social distancing measures be enforced, and the factors that governments should consider when deciding to lift them.

Now, a preliminary study carried out by the London School of Hygiene and Tropical Medicine has analysed the impact of physical distancing measures undertaken by the UK government on the transmission rate of the coronavirus.

From March 23 onwards, the UK implemented physical distancing measures, including instructing people to stay at home, to take one form of exercise a day and to go out only to buy essential items such as food or medicines. Schools, restaurants, bars and gyms were also ordered shut.

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What is the study about?

Through this study, researchers have surveyed 1,365 adults in the UK to analyse the impact that physical distancing measures have on the reproduction number, which refers to the average number of people infected by a COVID-19 positive person. The study notes a 73 per cent reduction in the average daily number of contacts observed per participant, which means a reduction from about 10.8 contacts per day to about 2.9. Researchers say that this reduction in contact will be enough to reduce the reproduction number of the coronavirus from 2.6 prior to the lockdown to about 0.62 after the lockdown measures were undertaken.

At 1,64,620 cases and 3,170 deaths, the US is now the worst hit country, overtaking both China (82,241 cases) and Italy (1,01,739 cases).

What does this mean?

In total, 1,365 UK adults who participated in the survey recorded over 3,849 contacts. While the study claims that there has been a reduction in the average daily number of contacts observed per participant, due to which, there might be a drop in the number of cases in the coming weeks, this may not result in an immediate decline.


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Referring to a similar study conducted in China, the study says that social distancing led to a reduction in the average number of contacts per day from 14.6 prior to the outbreak to 2 after the interventions. Even so, it is possible that those who participated in the UK survey responded because they were more actively adhering to the physical distancing measures, which could result in an overestimation of the effectiveness of the measures.

What have other researchers said?

A study published in the journal Lancet, which studied the effect of control strategies used to contain the infection in Wuhan, notes that physical distancing measures would be the most effective if they were lifted in the beginning of April. This would reduce the median number of infections by more than 92 per cent, the researchers claim, and by 24 per cent in mid-2020 and end-2020.


Alternatively, if these measures were gradually relaxed in March, the virus could start to resurge in the next three months in late June, and would peak in August. Therefore, relaxing the measures in April would buy time, for then, as per the researchers’ modeling, the virus would resurge two months later than June, in August and would peak in October.

People wearing face masks wait for a subway train on the first day the city’s subway services resumed following the novel coronavirus outbreak, in Wuhan of Hubei province. (Reuters Photo)

This means that lifting restrictions in Wuhan, which are scheduled to go on April 8, would delay the second peak of infections. Therefore, researchers suggest that lifting restrictions suddenly and prematurely could lead to an earlier second peak of infections. Essentially, what social distancing measures implemented by governments across the world aim to do is to delay the peak of infections, eventually reducing the “final size of the epidemic”.

Significantly, the alternative to mitigation measures involves testing, contact tracing and the localised quarantine of suspect cases. An article in the Lancet pointed out that the effectiveness of social distancing measures is determined by some factors such as the proportion of infected individuals that have mild symptoms, whether these individuals will self-isolate and to what effectiveness and how fast symptomatic cases isolate themselves after the onset of symptoms.

Here’s a quick Coronavirus guide from Express Explained to keep you updated: What can cause a COVID-19 patient to relapse after recovery? | COVID-19 lockdown has cleaned up the air, but this may not be good news. Here’s why | Can alternative medicine work against the coronavirus? | A five-minute test for COVID-19 has been readied, India may get it too | How India is building up defence during lockdown | Why only a fraction of those with coronavirus suffer acutely | How do healthcare workers protect themselves from getting infected? | What does it take to set up isolation wards?

First published on: 01-04-2020 at 22:23 IST
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