Reduce the risk of COVID-19 infection with humidity

The topic of COVID-19 is currently putting society to the test. The top priority is to reduce the risk of contagion and avoid a second wave of infections. In addition to hygiene measures, environmental factors such as humidity also influence the likelihood of infection. For this reason, scientific studies on the interplay between COVID-19, viral infections and the indoor climate in buildings are presented below.

Numerous studies have shown that a relative humidity of between 40 and 60% in buildings reduces the likelihood of virus transmission. Basically, three factors play a role:

1. Survivalof the virus depends on humidity

A recent Yale University study conducted by Moriyama, Hugentobler, and Iwasaki investigated the transmission of viruses and germs via direct or indirect contact, as well as through the air. When a person sneezes, germ droplets (medically aerosol) are sprayed into the room air. These droplets are a mixture of water, germs and salts and are directly affected by the relative humidity of the indoor air, regardless of whether they are still suspended in the air or adhering to a surface. Further scientific studies in this field of research have shown that the survival time of viruses is shortest at humidity between 40 and 60%.

2. Time the virus is suspended in the air

Viruses contained in the aerosol are highly infectious while the droplets are suspended in the air because they are inhaled directly into the lungs. At low humidity, the droplets quickly release a proportion of water into the room air, thus becoming lighter. They float less than 5 μm in the air, increasing the likelihood of transmission. If the air in the room is above 40%, small germ droplets absorb water from the room air, become heavier and settle more quickly on surfaces.

3. Effectivenessof the immune system at low humidity

Finally, the relative moisture content in the room air also influences the immune system. In dry air, the protective mechanism of the respiratory tract is restricted, as the mucus layers in the respiratory system, the respiratory tract and the lungs of humans, dry out. The movement of the cilia on the mucous membrane is restricted. As a result, viruses can no longer be transported away and fended off. At a humidity level of 40% or more, the immune system can work effectively and remove viruses from the respiratory tract.

If a moisture content of 40 to 60% were maintained in buildings, infections could be significantly reduced and the risk of infection could be minimized. That’s why we’ve put together presentations for you with information on LineMetrics use cases in offices, schools, hospitals, and retirement homes:

Download the presentation now:

• for schools and kindergartens
• for offices
• for retirement homes
• for hospitals
• for production facilities

Scientific studies on the topic:

• Moriyama, Miyu; Hugentobler, Walter J.; Iwasaki, Akiko (2020): Seasonality of Respiratory Viral Infections. In: Annual review of virology.
• Kudo, Eriko; Song, Eric; Yockey, Laura J.; Rakib, Tasfia; Wong, Patrick W.; Homer, Robert J.; Iwasaki, Akiko (2019): Low ambient humidity impairs barrier function and innate resistance against influenza infection. In: Proceedings of the National Academy of Sciences of the United States of America 116 (22), pp. 10905–10910.
• Noti, John D.; Blachere, Françoise M.; McMillen, Cynthia M.; Lindsley, William G.; Kashon, Michael L.; Slaughter, Denzil R.; Beezhold, Donald H. (2013): High humidity leads to loss of infectious influenza virus from simulated coughs. In: PloS one 8 (2), e57485.
• Tellier, Raymond (2009): Aerosol transmission of influenza A virus: a review of new studies. In: Journal of the Royal Society, Interface 6 Suppl 6, pp. 783-90.
• Leuven, Anice C.; Mubareka, Samira; Steel, John; Palese, Peter (2007): Influenza virus transmission is dependent on relative humidity and temperature. In: PLoS pathogens 3 (10), pp. 1470–1476.