Humidity and the COVID-19 Virus

Written by Gil Durrant August 27, 2020 0 comment

Humidity and the COVID-19 virus

Humidity and the COVID-19 Virus

The Evidence

A report in the Transboundary and Emerging Disease Journal raises the link between humidity and the Covid-19 virus. It suggests there is a link between relative humidity and an increase in community transmission. An estimate assumes that there is an increase of 7 to 8% in confirmed COVID-19 cases for every 1% drop in relative humidity.

This evidence indicates that there will be an increase in human to human transmission over winter. Relative humidity tends to decrease over this period as cold air holds less moisture.

Many people develop a dry throat and an irritating cough in winter due to dry air. Central heating and closed windows exacerbate this as the air becomes even drier due to evaporation.

The Reason

Why should the infection rate increase in winter? A significant factor is that people tend stay indoors more in winter often in close proximity to others. Many studies were carried out including at Yale University and the University of Sydney. Professor Michael Ward an epidemiologist at the University of Sydney explains that the droplets we exhale become smaller due to less moisture. This results in exhaled infectious aerosols staying suspended in the air for longer. In humid conditions the droplets are heavier and fall out of the air quicker.

Humidity and the COVID-19 virusThe Response

Based on such information higher humidity levels during winter months are desirable. The strategic placing of bowls of water over radiator cabinets will increase humidity levels somewhat. More humidity can be achieved using various types of diffusers or humidifiers examples of which can be found at

The Conclusion

It has been suggested that 40% to 60% relative humidity is ideal. However viral particles falling out of the air onto surfaces will still be a source of infection if touched. Therefore washing hands, cleaning surfaces, using masks and social distancing remain very important.

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