The last two days, a number of states in India have enforced measures aimed at reducing public gatherings. This is called “social distancing”.

How does social distancing work?

To stem the speed of the coronavirus spread so that healthcare systems can handle the influx, experts are advising people to avoid mass gatherings.
Offices, schools, concerts, conferences, sports events, weddings, and the like have been shut or cancelled around the world, including in a number of Indian states.
An advisory by the US Centers for Disease Control recommends social distancing measures such as: reducing the frequency of large gatherings and limiting the number of attendees; limiting inter-school interactions; and considering distance or e-learning in some settings.

What is the objective of such restrictions?

Compared to deadlier diseases such as bird flu, or H5N1, coronavirus is not as fatal —which ironically also makes it more difficult to contain.
With milder symptoms, the infected are more likely to be active and still spreading the virus.
For example, more than half the cases aboard a cruise ship that has docked in California did not exhibit any symptoms.
In a briefing on March 11, WHO officials said, “Action must be taken to prevent transmission at the community level to reduce the epidemic to manageable clusters.”
The main question for governments is to reduce the impact of the virus by flattening the trajectory of cases from a sharp bell curve to an elongated speed-bump-like curve.
This is being called “flattening the curve”. How does ‘flattening the curve’ help?
Limiting community transmission is the best way to flatten the curve.

What was the curve like in China?

The numbers show that the virus spread within Hubei exponentially but plateaued in other provinces.
Some say it’s because many of these countries learnt from the 2003 SARS epidemic.
Just as Chinese provinces outside of Hubei effectively stemmed the spread in February, three other countries —South Korea, Italy, and Iran — were not able to flatten the curve.

In epidemiology, the idea of slowing a virus’ spread so that fewer people need to seek treatment at any given time is known as “flattening the curve.”
It explains why so many countries are implementing “social distancing” guidelines — including a “lockdown” order that affects 1.3 billion people in India, even though COVID-19 outbreaks in various places might not yet seem severe.

The “curve” researchers are talking about refers to the projected number of people who will contract COVID-19 over a period of time.
To be clear, this is not a hard prediction of how many people will definitely be infected, but a theoretical number that’s used to model the virus’ spread. Here’s what one looks like:

The curve takes on different shapes, depending on the virus’s infection rate.
It could be a steep curve, in which the virus spreads exponentially (that is, case counts keep doubling at a consistent rate), and the total number of cases skyrockets to its peak within a few weeks.
Infection curves with a steep rise also have a steep fall; after the virus infects pretty much everyone who can be infected, case numbers begin to drop exponentially, too.
The faster the infection curve rises, the quicker the local health care system gets overloaded beyond its capacity to treat people.
As we’re seeing in Maharashtra or Ahmedabad, more and more new patients may be forced to go without ICU beds, and more and more hospitals may run out of the basic supplies they need to respond to the outbreak.
A flatter curve, on the other hand, assumes the same number of people ultimately get infected, but over a longer period of time.
A slower infection rate means a less stressed health care system, fewer hospital visits on any given day and fewer sick people being turned away.

Social Distancing and Flattening the Curve

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