Influenza Aerosols in UK Hospitals during the H1N1 (2009) Pandemic – The Risk of Aerosol Generation during Medical Procedures

Abstract

BackgroundNosocomial 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.Methodology/Principal FindingsThis 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/SignificanceWith 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.

Validation and Application of Models to Predict Facemask Influenza Contamination in Healthcare Settings

“…Thompson et al . reported that bronchoscopies produced exceedingly high levels (284,875 viruses/L) of detected influenza . If the value given for C out produced during a bronchoscopy were used in Equation , with all other variables kept at their likely level, the estimated FFR contamination would be over 100 million viruses, which is much higher than in any of the typical scenarios modeled in Table .…”

“…For example, aerosol‐generating procedures (such as bronchoscopy, intubation, ventilation, and nebulization) and source control (SM placement on the patient, bedside air filters, etc.) have the potential to significantly increase or decrease levels of airborne respiratory pathogens, respectively . Thompson et al .…”

Aerosol Transmission of Infectious Disease

“…92 Although there has been debate about whether influenza is transmitted through the airborne route, it is clearly transmitted through aerosols. Specifically, virus is emitted in aerosols from infectious people, 12 virus is present in the air around infectious people, 9,93 and infection has been demonstrated in human subjects subsequent to virus inhalation and intranasal instillation, 94,95 which are strong, moderate, and strong levels of evidence for conditions 1 to 3, respectively (Table 2). Seasonal influenza is a risk group 2 organism; novel influenza is in risk group 3.…”

“…[9][10][11][12] The range of particle sizes in an infectious aerosol depends on a number of factors including, but not limited to, the mechanism of aerosol generation and the liquid content and viscosity of the aerosolized fluid. 13 The liquid content of the particle influences the extent to which the particle size reduces with evaporation, although evaporation occurs rapidly, within a second of aerosol generation.…”

Time-Dependent Size-Resolved Bacterial and Fungal Aerosols in Beijing Subway

“…In addition, exposure to carcinogenic mycotoxins, e.g., aflatoxin and ochratoxin, can increase the risk of cancer (Douwes et al, 2003). Under some situations, airborne transmission of infectious agents among people could cause pandemics such as severe acute respiratory syndrome (SARS) and H1N1 flu (Yu et al, 2004;Thompson et al, 2013 Apart from many other bioaerosol investigations (Lee et al, 2011;Xu et al, 2011;Lee et al, 2012), there has been a boom of interest in its exposures for underground transportation. As an indispensable means of public transportation for urban metropolises, subway system around the globe is carrying the largest commuter traffic daily.…”