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

Méthode

La grippe nébulisée a été "toussée"  dans la salle d'examen et des échantillonneurs de bioaérosols ont collecté des aérosols fractionnés par taille (diamètres aérodynamiques <1 µM, 1 à 4 µM et > 4 µM) adjacents à la bouche du mannequin respiratoire et également à d'autres endroits dans la pièce. À température constante, l'HR variait de 7 à 73 % et l'infectivité a été évaluée par le test de plaque virale.

Résultats

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.