Empty roads, closed shops, no public transport, no social gatherings, major restrictions on stepping out of home — most living Indians have never experienced anything like this before. Neither have they experienced a global pandemic or faced a brand new virus that spreads so fast and stealthily through unsuspecting victims. This is our new reality in the wake of the COVID-19 pandemic, caused by the novel coronavirus (SARS-CoV‑2).

The Executive Director of the WHO‘s Health Emergencies Program, Michael Ryan said recently that a vaccine against SARS-CoV‑2 is at least a year away. With no vaccine or a cure in hand, strict preventive measures seem to be our only hope to control the COVID-19 outbreak. One such measure is ​“social”, or more accurately, ​“physical distancing”, which is deemed necessary by health officials all over the world. To enforce it, India went into a complete lockdown on the midnight of 25 March, 2020, joining several other countries that have imposed similar restrictions on their citizens in response to the pandemic. But will the lockdown, or the intended physical distancing, curb the outbreak?

In the midst of the ensuing public gloom across the world, researchers provide hope that the outbreak could indeed be slowed down if everyone practises physical distancing, whether they present the symptoms of the disease or not.

The symptoms under question are fever, dry cough and tiredness — the most common symptoms of COVID-19. Some patients may have runny nose, body pains, nasal congestion, sore throat or diarrhea. In more severe cases (1 out of every 6 patients), the person may also develop difficulty in breathing. 

Like with other respiratory infections, when someone with COVID-19 coughs, sneezes, or even talks, virus-laden droplets get released from their mouth. These droplets linger in the air for some time before falling on nearby objects where the viruses may survive for at least 3 hrs (in droplets in the air) to 72 hrs (on different surfaces). When someone inhales these droplets or touches a contaminated surface and then touches their mouth, nose or eyes, the virus enters their body. Washing hands regularly, not touching the face and covering the mouth while coughing or sneezing can indeed limit the spreading. But this is easier said than done.

Even if we wash our hands thoroughly, there is a very high chance of touching a contaminated surface between the washes, especially in a public place. Additionally, as most of us would have experienced by now, it takes a lot of discipline to keep our hands away from our faces. Researchers have observed that people normally touch their faces over 20 times an hour and nearly half of those contacts are with the nose, the mouth or the eyes- the main routes of respiratory infections, including COVID-19.

The following findings make the situation even more difficult. An analysis of the COVID-19 outbreak in February, 2020 on the​“Diamond Princess” cruise ship carrying 3711 people, and a study of 565 Japanese nationals who were evacuated from Wuhan, China the same month, revealed that ~30% of all the people infected with the novel coronavirus do not exhibit any symptoms of COVID-19, i.e., they are asymptomatic. In fact, mathematical modelling of the outbreak within a network of 375 cities in China estimated that ~86% of all the infected people are either asymptomatic or experience symptoms too mild to seek medical attention.

Now comes the catch. These individuals are infectious. They can spread the disease, despite the lack of symptoms. They may even cause severe symptoms in the people they come in contact with, especially the high-risk group that includes the elderly, and people with pre-conditions like diabetes, heart conditions and respiratory problems. 

The study which mathematically modelled the COVID-19 outbreak in China estimated that people with mild or no symptoms (hence undocumented) were only half as infectious as the documented patients. However, due to their larger numbers, these undocumented individuals were possibly the source of infection for ~79% of the documented cases. This happened before the Chinese government imposed travel restrictions and other preventive measures like physical distancing. 

Indeed, with the imposition of these restrictions, increased awareness, increased testing and stringent practice of physical distancing and personal hygiene, the rate of the spread of the virus in China reduced substantially, which aided their healthcare system in better managing the outbreak. The keywords here are ​“increased testing” and ​“physical distancing”. Let’s consider them one by one.

In India, as of 5 April, 2020, there are 192 testing labs for COVID-19. For a country with a population of 1.3 billion, that number corresponds to 1 testing lab for every 6.8 million Indians. Clearly, large-scale testing to identify and isolate all the infected people in the country is not feasible at this point. 

In fact, the Indian Council of Medical Research, the key decision-maker in all matters related to COVID-19 in India, currently allows testing of only a subset of the symptomatic people. Only the following categories of people are being tested as per the testing strategy revised on 20 March, 2020:

1. All symptomatic individuals who have undertaken international travel in the last 14 days:

2. All symptomatic contacts of laboratory-confirmed cases.

3. All symptomatic health care workers.

4. All hospitalized patients with Severe Acute Respiratory Illness (fever AND cough and/​or shortness of breath).

5. Asymptomatic direct and high-risk contacts of a confirmed case should be tested once between day 5 and day 14 of coming in his/​her contact.

People with no travel or contact history are not being tested.

Fortunately, most of the infected individuals will recover without any medical intervention. However, in light of the fact that many of them will be completely unaware of their infectiousness, their free movement can result in a deluge of patients needing critical care. Our healthcare system simply cannot handle such a deluge. This is where physical distancing becomes important.

Physical distancing essentially means reducing physical contact with other people. This includes working from home as much as possible and avoiding crowded places, non-essential travels and social gatherings. When it is absolutely needed to step outside, e.g., to buy essentials, or to see a doctor, it is important to stay at least 1 meter (3 feet) away from other people, as recommended by the WHO. This is the minimum distance needed to avoid inhaling the droplets released when someone coughs around you. Some public and private entities even encourage a 2‑meter rule to be on the safer side.

To help you visualize the importance of one meter, here is a video that describes how droplets from the mouth spread when people cough. 

Movement of droplets from the mouth while coughing. [Source: adapted from ​“Qualitative real-time schlieren and shadowgraph imaging of human exhaled airflows: an aid to aerosol infection control. Tang JW, et al. PLoS One. 2011”; CC-BY]

Hence, put simply, physical distancing helps in keeping a healthy person at a safe distance from an infected person- even an asymptomatic one. It thereby helps in slowing down the outbreak and eases the burden on the healthcare system, buying us some precious time.

“We need to use whatever time those measures [movement restrictions and physical distancing] are in place to put in place a public health architecture that can then go after the virus,” said WHO’s Michael Ryan in a press conference on 20 March, 2020. India’s healthcare system could use the bought time to create more testing labs, quarantine facilities, ICUs, and stock enough medicines and necessary equipment such as ventilators. This would help provide necessary care to all the patients who need it, hence reducing the mortality rate. (Figure: Why slowing down the outbreak is necessary)

As of 6 April, 2020, there are 3666 identified active cases of COVID-19 in India and 109 deaths from it. In the absence of a vaccine or a cure, physical distancing, in addition to practising respiratory and personal hygiene, is our best hope to slow down the outbreak. The more we slow it down, the more lives we will save. A lockdown may be highly inconvenient, but it is necessary for navigating the uncharted waters that we find ourselves in today.