Why humidifiers should be mandated in public spaces? (GREY-zones Part II)

how does it create Grey Zone to prevent Covid-19?

Vishal Gupta - DIRO

5 min readMar 28, 2020

A simple new study shows the Virus spread much slower in tropical malaria countries with a few exceptions.

Top 40 Malaria countries: — 212.24 malaria/1000 = 0.2 C19 cases per million
Next 40 Malaria countries: — 7.30 malaria/1000 = 10.1 C19 cases per million
154 No-Malaria countries: — ZERO malaria/1000 = 68.7 C19 cases per million

This is based upon the total number of COVID-19 cases as of March 17, 2020 as tallied by the WHO.

The spread in these countries could be lower because of following factors

Humidity
Temperature
Very low central air-conditioning
Immunity due to anti-malaria drugs (ignoring for this analysis)

Malaria countries are basically tropical and under-developed. This means low central air conditioning.

On the other side — a new report from CDC shows the Virus spreads 18.7 times faster in indoor environments.

Indoor environments in developed countries usually mean

Temperature around 18–20 degrees
Very low humidity — because of heating or air-conditioning.
Recirculating-air.

So considering both the slower spread in tropical undeveloped countries and faster spread inside buildings, — it is apparent that the COVID-19 spreads 18.7x faster in RECYCLED “dry” air from central air-conditioners or heating in cold countries.

Possible mechanisms of spread

Method 1 — dry air

Cold climates force people into closed buildings with central heating. Not only the weather is DRY outside but the heating or air-conditioners make the air dry inside buildings.

In case of dry weather of central heating the VIRUS is able to get air-borne because the VIRUS needs the water in the air to attach itself and drop to the surface.

Closed buildings provide a DRY environment for the VIRUS to spread. It spreads faster in cold climate via heating and otherwise in case of developed countries via recycled DRY air from the air-conditioners.

Method 2 —Lower Immunity

Another research further showed that low humidity negatively impacts the immune system’s defence against the flu virus in three ways.[1]

It stops the effective operation of cilia, which are tiny hair-like structures in our airways, from the trachea down into the lungs, that work to remove pollutants.
Secondly, it inhibits the ability of cells in the lungs damaged by the flu virus to repair themselves.
Lastly, the study indicated that low humidity caused a failure of signalling interferons released by infected cells to alert neighbouring cells to the virus, and thus fight its spread.

There are other studies that show that low ambient humidity impairs barrier function and innate resistance against influenza infection

Evidence COVID-19 becomes air-borne in air-conditioning

This pattern could be easily seen in the recent study of C19 spread in two long-distance commute busses in CHINA that were video-graphed and provided perfect cohorts.

By the study the Chinese government epidemiologists challenged the advice of health authorities and said — “It can be confirmed that in a closed environment with air-conditioning, the transmission distance of the new coronavirus will exceed the commonly recognised safe distance,” the researchers wrote in a paper published in peer-reviewed Chinese journal Practical Preventive Medicine.

Most people in the bus got infected (excluding ones wearing masks) without any surface to surface contact.

Solution — can humidifiers in public spaces stop this spread?

There are studies showing evidence of strong effectiveness of humidifiers in control of infection in hospitals.

“The survival times of SARS coronaviruses on inanimate surfaces and as infectious droplets in the air have been studied. An identical pattern has appeared repeatedly. Very low temperatures (tested at 6°C) and very low humidity (30%) enable viruses to survive for long periods on surfaces and in the air. Even at moderate temperatures of 20–30°C, there was a long survival time, but only when the air was dry. Very high temperatures (>30°C) render the coronaviruses inactive. This is why there have been repeated MERS epidemics on the Arabian Peninsula solely during the cooler winter months. It is assumed that the current Coronavirus will also exhibit a similar behavior in relation to humidity and temperature. The rate of transmission from human to human is influenced by indoor conditions,” explained Dr. Walter Hugentobler, FMH General Physician, and Dr. Stephanie Taylor, Harvard Medical School, Medical Advisors for Condair Group.

“Air humidification acts in a proactive way to combat the spread of viruses by infected people, including so-called super spreaders, even before any symptoms appear or a diagnosis can be made. Additionally, the respiratory tract’s defences are improved in all people due to the more efficient cleaning of the airways and enhanced immune defences. Raising air humidity by humidification reduces the risk of virus spread in hospitals and other buildings at low-cost and without causing negative effects,” said Hugentobler.

This means that conditions in homes and on public transport, where air is typically heated to 20 to 24 degrees for comfort, have resulting low relative humidity from approximately 20% to 40%. These are the ideal environmental conditions for SARS coronaviruses to survive on surfaces and in the air over a long period of time, and consequently for increased transmission via contact with contaminated surfaces and inhalation from the air. [2]

In another — a team at the Mayo Clinic, which humidified half of the classrooms in a preschool and left the other half alone over three months during the winter. Influenza-related absenteeism in the humidified classrooms was two-thirds lower than in the standard classrooms — a dramatic difference. Taylor a medical researcher and crusader on this subject says this study is important because its design included a control group: the half of classrooms without humidity-related intervention. (in a comprehensive Forbes articles covering the subject)

The problem has been — it takes on average of 17 years for scientific evidence to be put into medical practice, according to a classic study.

Why humidifiers are critical for creating a Grey Zone

Grey Zone is an open (non-quarantined) local region that does not let the VIRUS spread due to negative (below 1) R0 exponential factor. So any new seeds automatically die down. (Please refer to part 1)

Indoor environments cause 80%-90% of transmission

C19 having an R0 of 2.4 essentially means that the majority of the virus spreads in the indoor buildings through the air conditioning when corroborated with the above CDC study. It provides a breeding ground for C19 which is 18.7 times higher than fresh air environments.

Therefore it can be said — 2/3 of the 80% R0 in indoor environments can be reduced by mandating humidity control in public spaces.

Humidifiers can play a critical role to create regional grey zones and unlock economy or the critical public services.
And further, it will save millions of infection related deaths, billions in productivity annually while providing pandemic resilience.