title: Influenza virus in human exhaled breath: an observational study.
abstract: BACKGROUND
  Recent studies suggest that humans exhale fine particles during tidal breathing but little is known of their composition, particularly during infection.
  
  
  RESULTS
  We conducted a study of influenza infected patients to characterize influenza virus and particle concentrations in their exhaled breath. Patients presenting with influenza-like-illness, confirmed influenza A or B virus by rapid test, and onset within 3 days were recruited at three clinics in Hong Kong, China. We collected exhaled breath from each subject onto Teflon filters and measured exhaled particle concentrations using an optical particle counter. Filters were analyzed for influenza A and B viruses by quantitative polymerase chain reaction (qPCR). Twelve out of thirteen rapid test positive patients provided exhaled breath filter samples (7 subjects infected with influenza B virus and 5 subjects infected with influenza A virus). We detected influenza virus RNA in the exhaled breath of 4 (33%) subjects--three (60%) of the five patients infected with influenza A virus and one (14%) of the seven infected with influenza B virus. Exhaled influenza virus RNA generation rates ranged from <3.2 to 20 influenza virus RNA particles per minute. Over 87% of particles exhaled were under 1 microm in diameter.
  
  
  CONCLUSIONS
  These findings regarding influenza virus RNA suggest that influenza virus may be contained in fine particles generated during tidal breathing, and add to the body of literature suggesting that fine particle aerosols may play a role in influenza transmission.
authors.affiliation: Work Environment Department, University of Massachusetts Lowell, Lowell, Massachusetts, United States of America. patricia_fabian@uml.edu
authors.forename: Patricia
authors.initials: P
authors.lastname: Fabian
authors.forename: James J
authors.initials: JJ
authors.lastname: McDevitt
authors.forename: Wesley H
authors.initials: WH
authors.lastname: DeHaan
authors.forename: Rita O P
authors.initials: RO
authors.lastname: Fung
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Cowling
authors.forename: Kwok Hung
authors.initials: KH
authors.lastname: Chan
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Leung
authors.forename: Donald K
authors.initials: DK
authors.lastname: Milton
mesh_terms: D000293:Adolescent; D000328:Adult; D000388:Air; D001944:Breath Tests; D045853:Exhalation; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D009058:Mouth Breathing; D009975:Orthomyxoviridae / Q000378:metabolism*; D011138:Polytetrafluoroethylene; D012367:RNA, Viral / Q000032:analysis; D012119:Respiration
chemical_list: D012367:RNA, Viral; D011138:Polytetrafluoroethylene