Modeling the airborne survival of influenza virus in a residential setting: the impacts of home humidification

Abstract

BackgroundLaboratory research studies indicate that aerosolized influenza viruses survive for longer periods at low relative humidity (RH) conditions. Further analysis has shown that absolute humidity (AH) may be an improved predictor of virus survival in the environment. Maintaining airborne moisture levels that reduce survival of the virus in the air and on surfaces could be another tool for managing public health risks of influenza.MethodsA multi-zone indoor air quality model was used to evaluate the ability of portable humidifiers to control moisture content of the air and the potential related benefit of decreasing survival of influenza viruses in single-family residences. We modeled indoor AH and influenza virus concentrations during winter months (Northeast US) using the CONTAM multi-zone indoor air quality model. A two-story residential template was used under two different ventilation conditions - forced hot air and radiant heating. Humidity was evaluated on a room-specific and whole house basis. Estimates of emission rates for influenza virus were particle-size specific and derived from published studies and included emissions during both tidal breathing and coughing events. The survival of the influenza virus was determined based on the established relationship between AH and virus survival.ResultsThe presence of a portable humidifier with an output of 0.16 kg water per hour in the bedroom resulted in an increase in median sleeping hours AH/RH levels of 11 to 19% compared to periods without a humidifier present. The associated percent decrease in influenza virus survival was 17.5 - 31.6%. Distribution of water vapor through a residence was estimated to yield 3 to 12% increases in AH/RH and 7.8-13.9% reductions in influenza virus survival.ConclusionThis modeling analysis demonstrates the potential benefit of portable residential humidifiers in reducing the survival of aerosolized influenza virus by controlling humidity indoors.

Factors Associated with Post-Seasonal Serological Titer and Risk Factors for Infection with the Pandemic A/H1N1 Virus in the French General Population

“…In covariates related to the environmental characteristics of the housing, only the association between presence of an air humidifier in the living room and lower risk remained in the case-control multivariable model, which may be consistent with the possible impact of relative humidity on influenza aerosol transmission [65], [66].…”

Persistence of the 2009 Pandemic Influenza A (H1N1) Virus on N95 Respirators

“…As discussed previously, AH significantly impacts the survival of aerosolized influenza virus (24,29). Besides the present study, only one other study evaluated the survival of H1N1 on respirators (20).…”

Indoor temperature and humidity in New York City apartments during winter

“…This finding was in contrast to a few prior studies that have suggested that room humidification is effective at increasing absolute humidity levels in indoor environments. For example, a modeling exercise based on a two-story home in the Boston area suggested that a single humidifier turned on overnight in a bedroom could increase indoor VP from a baseline level of 7.5 mb to 10.4 mb (radiant heat model) or from 8.2 mb to 9.4mb (forced air heat model), corresponding to an estimated influenza virus survival decrease of 17.5–31.6% in the room with the humidifier operating (Myatt et al 2010). Further, an experiment in a Minnesota grade-school environment found that commercially available home humidification equipment was effective in raising the levels of humidity in classrooms, and could potentially reduce 1-h influenza virus survival rates from a maximum of 75% at low levels of humidity to about 35–45% using humidification (Koep et al 2013).…”

“…There are only a few studies that have monitored wintertime temperature and humidity inside homes in the United States (Arena et al 2010; Nguyen et al 2013; Tamerius et al 2013). Particularly, with few exceptions (Myatt et al 2010) there have been almost no studies that have investigated the effectiveness of attempts to humidify the wintertime residential environment.…”