Exposure to influenza virus aerosols during routine patient care

J Infect Dis. 2013 Apr;207(7):1037-46. doi: 10.1093/infdis/jis773. Epub 2013 Jan 30.


Background: Defining dispersal of influenza virus via aerosol is essential for the development of prevention measures.

Methods: During the 2010-2011 influenza season, subjects with influenza-like illness were enrolled in an emergency department and throughout a tertiary care hospital, nasopharyngeal swab specimens were obtained, and symptom severity, treatment, and medical history were recorded. Quantitative impaction air samples were taken not ≤0.305 m (1 foot), 0.914 m (3 feet), and 1.829 m (6 feet) from the patient's head during routine care. Influenza virus was detected by rapid test and polymerase chain reaction.

Results: Sixty-one of 94 subjects (65%) tested positive for influenza virus. Twenty-six patients (43%) released influenza virus into room air, with 5 (19%) emitting up to 32 times more virus than others. Emitters surpassed the airborne 50% human infectious dose of influenza virus at all sample locations. Healthcare professionals (HCPs) were exposed to mainly small influenza virus particles (diameter, <4.7 µm), with concentrations decreasing with increasing distance from the patient's head (P < .05). Influenza virus release was associated with high viral loads in nasopharyngeal samples (shedding), coughing, and sneezing (P < .05). Patients who reported severe illness and major interference with daily life also emitted more influenza virus (P < .05).

Conclusions: HCPs within 1.829 m of patients with influenza could be exposed to infectious doses of influenza virus, primarily in small-particle aerosols. This finding questions the current paradigm of localized droplet transmission during non-aerosol-generating procedures.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aerosols
  • Air Microbiology*
  • Child
  • Child, Preschool
  • Cough / virology
  • Cross Infection / pathology
  • Cross Infection / virology
  • Emergency Service, Hospital
  • Female
  • Health Personnel
  • Humans
  • Infectious Disease Transmission, Patient-to-Professional
  • Influenza, Human / transmission*
  • Inhalation Exposure / analysis*
  • Male
  • Middle Aged
  • Nasopharynx / virology
  • Orthomyxoviridae / genetics
  • Orthomyxoviridae / isolation & purification*
  • RNA, Viral / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Severity of Illness Index
  • Sneezing
  • Surveys and Questionnaires
  • Tertiary Care Centers
  • Viral Load
  • Young Adult


  • Aerosols
  • RNA, Viral