According to the latest research, humidity could have a significant part to play in the transmission and survival of the influenza A/H1N1 in areas where large numbers of people congregate such as in hospitals. This could have huge ramifications for the humidification industry and regulations for the built environment.

Researchers have known since the 1940s that low humidity levels increase the survival time of the flu virus. This, together with airborne transmission which is also affected by low humidity has been suggested as a factor for the seasonality of flu. The droplets expelled from a carrier, being water based, shrink rapidly due to evaporation in an environment that is less than 40% relative humidity (RH) and so remain airborne for long periods.

For many, increasing the environmental control of a building in winter would simply involve increasing the air temperature to a comfortable level of around 22°C. However, this heating effect without the inclusion of humidity control reduces the RH levels to those below 25%. According to the latest research by Dr Jeffrey Shaman at Oregon State University, absolute humidity (water in the air) is the defining factor and can greatly reduce the viability of flu virus and the transmission of influenza.

Even the South West Hampshire Primary Care Trust’ own Management of Pandemic Influenza claims virus survival is “enhanced in conditions of cold temperature and low relative humidity.”

With Dr Shaman’s findings supporting a requirement for humidification and with so many hospital builds focusing on air tightness maybe health estate managers should be questioning this strategy. The extent to which moisture has a part to play in our environments is well documented but its impact on our health poses many questions, the answers of which could have a major impact on our hospitals’ environments, their patients, visitors and employees.

E-mail Eaton-Williams