Respiratory Protection for Healthcare Workers: A Controversy

Risk to Healthcare Professionals

The September 2010 updated CDC influenza infection control guidelines acknowledge that airborne transmission of influenza may occur "via small particle aerosols in the immediate vicinity of the infectious individual" but states that the "relative contribution of the different modes of influenza transmission is unclear" and also that surgical masks by design do not seal closely to the face and do not prevent inhalation of small particles that may be transmitted by exhalation, coughs, or certain medical procedures.^[19] Thus, the use of a surgical mask instead of a fit-tested N95 respirator during patient care activities may increase the risk for influenza transmission to HCP.

Respirators cost more than surgical masks, must be fit-tested, and can be uncomfortable to wear. In addition, in parts of the world with limited resources, such devices may not be readily available or affordable. Is the risk that influenza infection presents to HCP sufficient to require the use of respirators during the care of influenza patients? Widespread vaccination of HCP for seasonal influenza should substantially reduce this risk across the workforce when there is a good match between the vaccine and circulating influenza strains. Effective implementation of other recommended influenza prevention and control strategies will further reduce the risk.^[19]

Current infection control recommendations are based on transmission characteristics of specific infectious diseases, and the risk that these diseases pose to HCP is not considered. Assessing the risk for specific pathogens to HCP is another factor to consider when determining the appropriate PPE.

The US National Institutes of Health (NIH), the World Health Organization, and organizations in other countries have classified infectious microorganisms by risk group. Such classification could be incorporated into an assessment process to determine appropriate PPE recommendations. One example of risk classification is the system established by the NIH for infectious microorganisms in laboratories (Table).^[35]

Table. Classification of Infectious Microorganisms by Risk Group

Risk Group Classification	NIH Guidelines for Research Involving Recombinant DNA Molecules 2002
Risk Group 1	Agents not associated with disease in healthy adult humans
Risk Group 2	Agents associated with human disease that is rarely serious and for which preventive or therapeutic interventions are often available
Risk Group 3	Agents associated with serious or lethal human disease for which preventive or therapeutic interventions may be available (high individual risk but low community risk)
Risk Group 4	Agents likely to cause serious or lethal human disease for which preventive or therapeutic interventions are not usually available (high individual risk and high community risk)

From the National Institutes of Health. Available at:
https://oba.od.nih.gov/oba/rac/guidelines_02/NIH_Gdlines_2002prn.pdf.^[35]

An attempt to provide a framework for the selection of respiratory protection on the basis of risk assessment has been published. In addition to pathogen risk group, factors assessed included ventilation rates and types of host emissions (eg, cough, aerosol-generating procedures).^[36] Other host characteristics such as age and where the host is in the clinical course of illness may also be important factors in infectiousness. For example, it is well known that children with tuberculosis are not as infectious as adults.^[2] In addition, some hosts may be more effective transmitters of respiratory pathogens ("super spreaders"), although it is not currently possible to determine this preemptively.

Respiratory Protection for TB and Other Bacterial Pathogens

In addition to influenza and other respiratory viruses, bacterial pathogens may also be transmitted through respiratory aerosols. Mycobacterium tuberculosis is a well-known example of a bacterial pathogen transmitted by this route; however, another example is Bordetella pertussis. B pertussis has a reproduction number similar to that of measles, a highly infectious viral disease classified as airborne.^[37] In early studies of fatal cases, B pertussis was frequently isolated from the alveoli and less commonly from the trachea or bronchi, suggesting that the bacteria had been inhaled.^[38,39] In addition, a recent report described possible aerosol transmission of Neisseria meningitidis.^[40]

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