title: Influenza aerosols in UK hospitals during the H1N1 (2009) pandemic--the risk of aerosol generation during medical procedures.
abstract: BACKGROUND
  Nosocomial infection of health-care workers (HCWs) during outbreaks of respiratory infections (e.g. Influenza A H1N1 (2009)) is a significant concern for public health policy makers. World Health Organization (WHO)-defined 'aerosol generating procedures' (AGPs) are thought to increase the risk of aerosol transmission to HCWs, but there are presently insufficient data to quantify risk accurately or establish a hierarchy of risk-prone procedures.
  
  
  RESULTS
  This study measured the amount of H1N1 (2009) RNA in aerosols in the vicinity of H1N1 positive patients undergoing AGPs to help quantify the potential risk of transmission to HCWs. There were 99 sampling occasions (windows) producing a total of 198 May stages for analysis in the size ranges 0.86-7.3 µm. Considering stages 2 (4-7.3 µm) and 3 (0.86-4 µm) as comprising one sample, viral RNA was detected in 14 (14.1%) air samples from 10 (25.6%) patients. Twenty three air samples were collected while potential AGPs were being performed of which 6 (26.1%) contained viral RNA; in contrast, 76 May samples were collected when no WHO 2009 defined AGP was being performed of which 8 (10.5%) contained viral RNA (unadjusted OR = 2.84 (95% CI 1.11-7.24) adjusted OR = 4.31 (0.83-22.5)).
  
  
  CONCLUSIONS
  With our small sample size we found that AGPs do not significantly increase the probability of sampling an H1N1 (2009) positive aerosol (OR (95% CI) = 4.31 (0.83-22.5). Although the probability of detecting positive H1N1 (2009) positive aerosols when performing various AGPs on intensive care patients above the baseline rate (i.e. in the absence of AGPs) did not reach significance, there was a trend towards hierarchy of AGPs, placing bronchoscopy and respiratory and airway suctioning above baseline (background) values. Further, larger studies are required but these preliminary findings may be of benefit to infection control teams.
authors: Biosafety Investigation Unit, Health Protection Agency, Porton Down, Wiltshire, United Kingdom. Katy-Anne.Thompson@hpa.org.uk
authors: Katy-Anne
authors: KA
authors: Thompson
authors: John V
authors: JV
authors: Pappachan
authors: Allan M
authors: AM
authors: Bennett
authors: Himanshu
authors: H
authors: Mittal
authors: Susan
authors: S
authors: Macken
authors: Brian K
authors: BK
authors: Dove
authors: Jonathan S
authors: JS
authors: Nguyen-Van-Tam
authors: Vicky R
authors: VR
authors: Copley
authors: Sarah
authors: S
authors: O'Brien
authors: Peter
authors: P
authors: Hoffman
authors: Simon
authors: S
authors: Parks
authors: Andrew
authors: A
authors: Bentley
authors: Barbara
authors: B
authors: Isalska
authors: Gail
authors: G
authors: Thomson
mesh_terms: D000293:Adolescent; D000328:Adult; D000336:Aerosols / Q000032:analysis*; D000368:Aged; D000391:Air Microbiology / Q000592:standards; D001999:Bronchoscopy / Q000706:statistics & numerical data; D002648:Child; D002675:Child, Preschool; D003428:Cross Infection / Q000517:prevention & control* / Q000821:virology; D005260:Female; D006801:Humans; D017758:Infectious Disease Transmission, Patient-to-Professional / Q000517:prevention & control; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D007362:Intensive Care Units / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D058873:Pandemics / Q000517:prevention & control; D012367:RNA, Viral / Q000235:genetics; D012137:Respiratory System / Q000821:virology; D018570:Risk Assessment; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology; D014944:World Health Organization; D055815:Young Adult
chemical_list: D000336:Aerosols; D012367:RNA, Viral