Since you are reading this story, there is a strong chance that you have heard about The Indoor Generation campaign at some point of time in the past two years. You might also have watched a short-film in which a young girl warns us all about the dangers of staying indoors, without realizing to what extent.

"This is the story about us," that little girl says. The novel coronavirus, or SARS-CoV-2, is somehow reminding us of the same message. While there is a clamour for ramping up the number of ventilators in hospitals, researches show having proper ventilation in our homes and work places is a better shield against Covid-19.

A study published in Nature towards April-end compared the presence of the novel coronavirus in the environs of two hospitals in China to ascertain the aerodynamics of SARS-CoV-2. Researches found that the concentration of the novel coronavirus was very high in closed spaces and extremely low in properly ventilated places, including Covid-19 patients' rooms.

The researchers did not study the infectivity of the novel coronavirus. But they said, "Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols."

Why is this significant?

Novel coronaviruses spread through aerosols and droplets. Aerosols are considered more potent because they are very light and can remain suspended in air for a longer duration. Droplets tend to settle down on surfaces faster.

Both aerosols and droplets emerge from humans when they speak, cough, sneeze, sing or spit. A Covid-19 positive person can release millions of novel coronaviruses in a single cough or sneeze or while speaking a single sentence.

SARS-CoV-2 can stay active outside the human body anywhere between three hours in the form of suspended aerosols to 72 hours on surfaces such as plastic.

If someone inhales the aerosol contaminated by novel coronaviruses or touches a surface that has droplets with these viruses, the person is likely to get the infection when she touches her mouth or face next time. This may happen within 20 minutes.

There is no conclusive evidence yet to say what has more infectivity: an aerosol reaching one's nostrils or lungs. Droplets being larger in size don't usually reach the lungs. What is agreed now is that infection begins in the upper respiratory tract just beyond the nostrils or at the back of the throat.

Once the virus is inside the system, there is no magic cure yet. Vaccines are still at least a year away. Symptomatic treatment is being given. But there is a shield which is made up of physical distancing, wearing masks and now opening windows of our rooms.

Besides the study cited above about the aerodynamics of SARS-CoV-2, three other research papers are being frequently referred to in finding ways to prevent Covid-19 spread.

One of these is about a much quoted case of Covid-19 spread in China, when one person infected nine others in a restaurant. The researchers concluded that the air conditioner was the infection spreader. All people in the range of the AC got the virus while others tested negative for Covid-19.

Another study is from South Korea. Here, 94 people got the infection on an office floor. They were on the same side of the building and shared a centralised air cooling system.

The third study that apparently provides an answer to why people were getting infected in a closed space even when they maintained social distancing and did not interact with one another. This is aerodynamics of novel coronavirus. It spreads through air.

But this study showed something else as well. It shows every cluster outbreak of Covid-19 involved three or more people (almost 82 per cent) in indoor environments. In most cases, these indoor environments are homes (about 80 per cent), air conditioned public transport means (34 per cent - overlapping with homes, others), or restaurants.

The researchers identified only a single outbreak in an outdoor environment, which involved two cases. They concluded, "The transmission of respiratory infections such as SARS-CoV-2 from the infected to the susceptible is an indoor phenomenon."

So, open your windows but don't go outside unless necessary because crowding too creates an invisible indoor environ.

Interestingly, a 2019 study found that windows and other means of natural ventilation can reduce transmission of tuberculosis (TB) by up to 72 per cent. One of top killers and leading cause of death among HIV/AIDS patients, TB killed 15 lakh people worldwide in 2018. India leads the count of TB deaths.