Non-Pharmaceutical Interventions for Flu and COVID-19
Some simple steps to boost immune response to and reduce the risk of respiratory viruses.
Although social distancing, hand washing, and mask wearing are now well established recommendations for limiting COVID-19 spread, there may be other simple changes that could reduce spread or limit disease severity.
Increasing the humidity at home is one simple step. An article from May 2019 reported that increasing the humidity from 10–20% to 40–60% reduced the severity of influenza infection in mice.
Another study from 2018 supports the benefits of humidified air in reducing influenza transmission. This study evaluated the effect of humidifying the air in a classroom setting also supports a reduction in transmission. Preschool classrooms in Minnesota were either humidified to ~45% relative humidity or not humidified during months when the heat (January to March). The amount influenza virus in the air and on objects commonly touched by the students was measured. Compared with the control classrooms, the humidified classrooms had fewer samples that were positive for influenza virus (both air samples and object samples) and the amount of viral genome detected was also less. Additionally, fewer students from the humidified classrooms were absent due to illness or with influenza-like symptoms, consistent with a benefit from humidifying the environment.
Relative humidity between 40% and 60% helps in the following ways:
- Promotes clearance of mucus and virus from the upper respiratory passages (Kudo and colleagues)
- Boosts the innate immune response to viruses (Kudo and colleagues)
- Prevents damage to epithelial cells (Moriyama and colleagues)
- Supports repair of damaged epithelial cells (Kudo and colleagues)
- Reduces virus on surfaces (Reiman and colleagues)
- Reduces virus in the air (Reiman and colleagues)
- Reduces viral infection and transmission (Moriyama and colleagues, Reiman and colleagues)
I found these results so intriguing that I set up 3 humidifiers in my own home. I will keep them going as long as I am heating my home.
Other simple measures that can be used to reduce the spread or severity of respiratory infections include:
- Wear a face covering to reduce spread of particles from coughs, sneezes, or speech and to keep the nose warm and moist (Moriyama and colleagues)
- Ensure adequate vitamin D either through sufficient skin exposure to sunlight or a supplement (during periods of short daylight or if lack of sun exposure) to support the immune system (Martineau and colleagues)
- Get sufficient sleep (~7 hours per day) to support the immune system (Besedovsky and colleagues)
- Limit alcohol intake to support the immune system (Zaldivar Fujigaki and colleagues, Hemann and colleagues, and Zacharias and Legge)
- Ventilate indoor air (open the windows) to disperse the virus (Moriyama and colleagues)
- Wash hands frequently
- Use social distancing to minimize exposure
References
Besedovsky L, Lange T, Haack M. The Sleep-Immune Crosstalk in Health and Disease. Physiol. Rev. 99, 1325‐1380 (2019). DOI: 10.1152/physrev.00010.2018
Kudo E, Song E, Yockey LJ, et al. Low ambient humidity impairs barrier function and innate resistance against influenza infection. Proc. Natl. Acad. Sci. U. S. A. 116, 10905‐10910 (2019). DOI: 10.1073/pnas.1902840116
Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 356, i6583 (2017) DOI: 10.1136/bmj.i6583
Moriyama M, Hugentobler WJ, Iwasaki A. Seasonality of Respiratory Viral Infections. Annu. Rev. Virol. 10.1146/annurev-virology-012420–022445 [published online ahead of print, 2020 Mar 20]. DOI: 10.1146/annurev-virology-012420–022445
Reiman JM, Das B, Sindberg GM, et al. Humidity as a non-pharmaceutical intervention for influenza A. PLoS One 13, e0204337 (2018). DOI: 10.1371/journal.pone.0204337
Zacharias ZR, Legge KL. Chronic Ethanol Consumption Reduces Existing CD8 T Cell Memory and Is Associated with Lesions in Protection against Secondary Influenza A Virus Infections. J. Immunol. 203,3313‐3324 (2019). DOI: 10.4049/jimmunol.1900770
Zaldivar Fujigaki JL, Arroyo Valerio AG, López Alvarenga JC, Gutiérrez Reyes EG, Kershenobich D, Hernández Ruiz J. Alterations in Activation, Cytotoxic Capacity and Trafficking Profile of Peripheral CD8 T Cells in Young Adult Binge Drinkers. PLoS One 10, e0132521 (2015). DOI: 10.1371/journal.pone.0132521
