title: Transmission of aerosolized seasonal H1N1 influenza A to ferrets.
abstract: Influenza virus is a major cause of morbidity and mortality worldwide, yet little quantitative understanding of transmission is available to guide evidence-based public health practice. Recent studies of influenza non-contact transmission between ferrets and guinea pigs have provided insights into the relative transmission efficiencies of pandemic and seasonal strains, but the infecting dose and subsequent contagion has not been quantified for most strains. In order to measure the aerosol infectious dose for 50% (aID(50)) of seronegative ferrets, seasonal influenza virus was nebulized into an exposure chamber with controlled airflow limiting inhalation to airborne particles less than 5 µm diameter. Airborne virus was collected by liquid impinger and Teflon filters during nebulization of varying doses of aerosolized virus. Since culturable virus was accurately captured on filters only up to 20 minutes, airborne viral RNA collected during 1-hour exposures was quantified by two assays, a high-throughput RT-PCR/mass spectrometry assay detecting 6 genome segments (Ibis T5000™ Biosensor system) and a standard real time RT-qPCR assay. Using the more sensitive T5000 assay, the aID(50) for A/New Caledonia/20/99 (H1N1) was approximately 4 infectious virus particles under the exposure conditions used. Although seroconversion and sustained levels of viral RNA in upper airway secretions suggested established mucosal infection, viral cultures were almost always negative. Thus after inhalation, this seasonal H1N1 virus may replicate less efficiently than H3N2 virus after mucosal deposition and exhibit less contagion after aerosol exposure.
authors.affiliation: Program in Infectious Disease, Lovelace Respiratory Research Institute, Albuquerque, New Mexico, United States of America.
authors.forename: Heather
authors.initials: H
authors.lastname: MacInnes
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhou
authors.forename: Kristine
authors.initials: K
authors.lastname: Gouveia
authors.forename: Jenna
authors.initials: J
authors.lastname: Cromwell
authors.forename: Kristin
authors.initials: K
authors.lastname: Lowery
authors.forename: R Colby
authors.initials: RC
authors.lastname: Layton
authors.forename: Michael
authors.initials: M
authors.lastname: Zubelewicz
authors.forename: Rangarajan
authors.initials: R
authors.lastname: Sampath
authors.forename: Steven
authors.initials: S
authors.lastname: Hofstadler
authors.forename: Yushi
authors.initials: Y
authors.lastname: Liu
authors.forename: Yung-Sung
authors.initials: YS
authors.lastname: Cheng
authors.forename: Frederick
authors.initials: F
authors.lastname: Koster
mesh_terms: D000336:Aerosols; D000388:Air; D000818:Animals; D002460:Cell Line; D002642:Chick Embryo; D046508:Culture Techniques; D004285:Dogs; D005289:Ferrets; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D009330:Nebulizers and Vaporizers; D009976:Orthomyxoviridae Infections / Q000635:transmission*; D016133:Polymerase Chain Reaction; D011138:Polytetrafluoroethylene / Q000737:chemistry; D013997:Time Factors; D014771:Virion / Q000235:genetics / Q000302:isolation & purification
chemical_list: D000336:Aerosols; D011138:Polytetrafluoroethylene