Last updated on Jun 23rd, 2021 at 10:00 am

With the coronavirus being a highly contagious respiratory virus, is there anything we can do to reduce indoor COVID-19 airborne transmissions?

We’re all worried about the potential for airborne transmission of the novel coronavirus in our homes and offices.

Although physical distancing and washing your hands help, the virus can be airborne and when that happens indoors, it’s concerning.

How respiratory viruses spread

To help find potential solutions, Yale University scientists reviewed studies on how respiratory viruses are transmitted.

They found that the cold, dry air of winter clearly helps SARS-CoV2 – the virus that causes COVID-19 – spread among people. However, they found that as humidity increases during spring and summer, the risk of transmission of the virus through airborne particles decreases both outside and indoors in places such as offices.

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While viruses can still be transmitted through direct contact or through contaminated surfaces as humidity rises, research suggests that the difference between outside humidity and temperatures and indoor humidity could be an ally in slowing rates of viral transmission.

“Ninety percent of our lives in the developed world is spent indoors in close proximity to one another,” says Yale immunobiologist and senior author Akiko Iwasaki. “What has not been talked about is the relationship of temperature and humidity in the air indoors and outdoors and aerial transmission of the virus.”

How long does the coronavirus last on surfaces and could it be in the air?

Why viruses thrive in cold, dry air

Winter’s cold, dry air makes such viruses a triple threat.

When cold outdoor air with little moisture is heated indoors, the air’s relative humidity drops to about 20%. This comparatively moisture-free air provides a clear path for airborne viral particles of viruses such as COVID-19,” explains Prof Iwasaki.

Warm, dry air also dampens the ability of cilia, the hair-like projections on cells lining airways, to expel viral particles. And lastly, the immune system’s ability to respond to pathogens is suppressed in drier environments.

What can we do?

Prof Iwasaki’s review cites experiments that show that rodents infected with respiratory viruses can easily transmit viral particles through the air to non-infected neighbours in low-humidity environments.

That’s why I recommend humidifiers during the winter in buildings,” says Prof Iwasaki.

So using a humidifier in your home and office could help reduce the possibility of airborne transmissions, but it’s not a cure-all. In fact, the main problems are poorly ventilated spaces and cramped spaces.

“Many homes and buildings are poorly ventilated and people often live in close proximity and in these cases, the benefits of higher humidity are mitigated.”

Iwasaki stresses that these studies only apply to aerosol transmission – the virus still can be shared at any time of year between people in close proximity and through contact with surfaces containing sufficient amounts of virus. That is why people living in warm countries and people working close to each other are still susceptible to infection, she said.

“It doesn’t matter if you live in Singapore, India, or the Arctic, you still need to wash your hands and practise social distancing,” says Prof Iwasaki.

Source: Yale University via

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