Published: 27/02/13 | PLoS One. 2013; 8 (2):e57485

High humidity leads to loss of infectious influenza virus from simulated coughs

John D. Noti, Francoise M. Blachere, Cynthia M. McMillen, William G. Lindsley, Michael L. Kashon, Denzil R. Slaughter, Donald H. Beezhold


Method

Nebulized influenza was coughed into the examination room and Bioaerosol samplers collected size-fractionated aerosols (<1 µM, 1–4 µM, and >4 µM aerodynamic diameters) adjacent to the breathing manikin’s mouth and also at other locations within the room. At constant temperature, the RH was varied from 7–73% and infectivity was assessed by the viral plaque assay.

Results

Total virus collected for 60 minutes retained 70.6–77.3% infectivity at relative humidity ≤23% but only 14.6–22.2% at relative humidity ≥43%. Analysis of the individual aerosol fractions showed a similar loss in infectivity among the fractions. Time interval analysis showed that most of the loss in infectivity within each aerosol fraction occurred 0–15 minutes after coughing. Thereafter, losses in infectivity continued up to 5 hours after coughing, however, the rate of decline at 45% relative humidity was not statistically different than that at 20% regardless of the aerosol fraction analyzed.

Conclusion

At low relative humidity, influenza retains maximal infectivity. Inactivation of the virus at higher relative humidity occurs rapidly after coughing. Although virus carried on aerosol particles <4 µM have the potential for remaining suspended in air currents longer and traveling further distances than those on larger particles, their rapid inactivation at high humidity tempers this concern. Maintaining indoor relative humidity >40% will significantly reduce the infectivity of aerosolized virus.

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par Dr.med. Walter Hugentobler

"Cette étude récente a montré qu'une humidité de l'ordre de 40 à 60 % HR avait un effet néfaste sur le virus de la grippe aéroporté, le rendant rapidement inoffensif.

Il renforce le niveau d'humidité inférieur dans les locaux publics et commerciaux doit être maintenu à plus de 40% HR pour réduire les infections aéroportées

Cela est particulièrement vrai dans des environnements comme les cabinets médicaux, les hôpitaux et les établissements de santé où il y a un plus grand nombre de personnes infectées et d'autres qui sont particulièrement vulnérables.

Le niveau d'humidité critique de 40 à 45% HR comme limite inférieure a été renforcé au cours de décennies de recherche dans d'innombrables études".

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