title: Modeling the airborne survival of influenza virus in a residential setting: the impacts of home humidification.
abstract: BACKGROUND
  Laboratory 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.
  
  
  METHODS
  A 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  This modeling analysis demonstrates the potential benefit of portable residential humidifiers in reducing the survival of aerosolized influenza virus by controlling humidity indoors.
authors.affiliation: Environmental Health & Engineering, Inc, Needham, MA, USA. tmyatt@eheinc.com
authors.forename: Theodore A
authors.initials: TA
authors.lastname: Myatt
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Kaufman
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Allen
authors.forename: David L
authors.initials: DL
authors.lastname: MacIntosh
authors.forename: M Patricia
authors.initials: MP
authors.lastname: Fabian
authors.forename: James J
authors.initials: JJ
authors.lastname: McDevitt
mesh_terms: D000391:Air Microbiology; D006801:Humans; D006813:Humidity; D009980:Influenza A virus / Q000254:growth & development*; D007251:Influenza, Human / Q000635:transmission*; D050296:Microbial Viability; D010316:Particle Size; D038301:Virus Inactivation
references.citation: Lancet Infect Dis. 2007 Dec;7(12):759-60; author reply 761-3
references.pmid: 18045555
references.citation: J Exp Med. 1948 Sep 1;88(3):361-8
references.pmid: 18881494
references.citation: Proc Natl Acad Sci U S A. 2009 Mar 10;106(10):3645-6
references.pmid: 19276125
references.citation: Arch Virol. 1976;51(4):263-73
references.pmid: 987765
references.citation: J Hyg (Lond). 1961 Dec;59:479-86
references.pmid: 13904777
references.citation: Am Rev Respir Dis. 1967 Dec;96(6):1137-43
references.pmid: 6057616
references.citation: PLoS Pathog. 2013 Mar;9(3):e1003205
references.pmid: 23505369
references.citation: Ann Occup Hyg. 1978 Aug;21(2):177-90
references.pmid: 697270
references.citation: J Hyg (Lond). 1963 Sep;61:331-5
references.pmid: 14066589
references.citation: Risk Anal. 2009 Sep;29(9):1292-303
references.pmid: 19558389
references.citation: Nature. 1962 Sep 15;195:1063-4
references.pmid: 13874315
references.citation: Proc Natl Acad Sci U S A. 2009 Mar 3;106(9):3243-8
references.pmid: 19204283
references.citation: J Infect Dis. 1950 Sep-Oct;87(2):128-32
references.pmid: 14774528
references.citation: Occup Environ Med. 1994 Oct;51(10):683-8
references.pmid: 8000493
references.citation: Emerg Infect Dis. 2006 Nov;12(11):1657-62
references.pmid: 17283614
references.citation: PLoS Biol. 2010 Feb 23;8(2):e1000316
references.pmid: 20186267
references.citation: Environ Health. 2008 Aug 06;7:43
references.pmid: 18684328
references.citation: Appl Environ Microbiol. 2010 Jun;76(12):3943-7
references.pmid: 20435770
references.citation: Lancet Infect Dis. 2007 Apr;7(4):257-65
references.pmid: 17376383
references.citation: J Infect Dis. 2006 Nov 1;194 Suppl 2:S82-91
references.pmid: 17163394
references.citation: Nature. 1960 Oct 29;188:430-1
references.pmid: 13713229
references.citation: J Hyg (Lond). 1943 Jan;43(1):1-10
references.pmid: 20475657
references.citation: Arch Environ Health. 1992 Jan-Feb;47(1):8-15
references.pmid: 1540009
references.citation: J Expo Sci Environ Epidemiol. 2007 May;17(3):288-97
references.pmid: 17033678
references.citation: Ann Allergy. 1971 Jul;29(7):356-7
references.pmid: 5096828
references.citation: J Environ Monit. 2009 Feb;11(2):314-7
references.pmid: 19212587
references.citation: PLoS One. 2008 Jul 16;3(7):e2691
references.pmid: 18628983
references.citation: PLoS Pathog. 2007 Oct 19;3(10):1470-6
references.pmid: 17953482