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Safety Precautions and Operating Procedures in an ABSL-4 Laboratory: 3. Aerobiology
Published on: October 3, 2016
Airborne transmission and precautions: facts and myths
1University of Hong Kong, School of Public Health, Hong Kong, SAR, China.
Abstract:
Airborne transmission occurs only when infectious particles of <5 μm, known as aerosols, are propelled into the air. The prevention of such transmission is expensive, requiring N95 respirators and negative pressure isolation rooms. This lecture first discussed whether respiratory viral infections are airborne with reference to published reviews of studies before 2008, comparative trials of surgical masks and N95 respirators, and relevant new experimental studies. However, the most recent experimental study, using naturally infected influenza volunteers as the source, showed negative results from all the manikins that were exposed. Modelling studies by ventilation engineers were then summarized to explain why these results were not unexpected. Second, the systematic review commissioned by the World Health Organization on what constituted aerosol-generating procedures was summarized. From the available evidence, endotracheal intubation either by itself or combined with other procedures (e.g. cardiopulmonary resuscitation or bronchoscopy) was consistently associated with increased risk of transmission by the generation of aerosols.
Insights
Respiratory viral infections are not consistently airborne, despite aerosol generation concerns. Endotracheal intubation is linked to higher transmission risk via aerosols.
Area of Science:
- Infectious disease transmission
- Aerosol science
- Respiratory health
Background:
- Airborne transmission of infectious particles (<5 μm aerosols) necessitates costly N95 respirators and negative pressure isolation.
- Understanding the airborne nature of respiratory viral infections is crucial for effective prevention strategies.
Purpose of the Study:
- To critically evaluate the evidence for airborne transmission of respiratory viral infections.
- To identify aerosol-generating procedures (AGPs) associated with increased transmission risk.
Main Methods:
- Review of pre-2008 studies on airborne transmission of respiratory viruses.
- Analysis of comparative trials of surgical masks versus N95 respirators.
- Examination of recent experimental studies, including those with naturally infected influenza volunteers.
- Summarization of modeling studies by ventilation engineers.
- Systematic review by the World Health Organization on aerosol-generating procedures.
Main Results:
- Recent experimental studies using influenza volunteers yielded negative results for airborne transmission across exposed manikins.
- Ventilation engineering models explain the unexpected negative results.
- Endotracheal intubation, with or without other procedures like CPR or bronchoscopy, was consistently linked to higher transmission risk due to aerosol generation.
Conclusions:
- Evidence does not consistently support airborne transmission of all respiratory viral infections.
- Specific procedures, notably endotracheal intubation, pose a significant risk for aerosol-mediated transmission.
- Further research and targeted infection control measures for high-risk procedures are warranted.
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