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October 4, 2000

Safety Precautions to Limit Exposure From Plague-Infected Patients

Author Affiliations

Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Executive Deputy EditorIndividualAuthor

JAMA. 2000;284(13):1648-1649. doi:10.1001/jama.284.13.1647

To the Editor: Dr Ingelsby and colleagues1 recommend isolation of patients with pneumonic plague to prevent droplet (usually defined as particles larger than 5 µ) transmission. Isolation of this type only includes the use of surgical masks when standing within 1 m of the patient (because large droplets do not settle beyond 1 m of the patient) and no special ventilation systems.2 However, if airborne particles are aerosolized (ie, are smaller than 5 µ), then well-ventilated rooms under negative pressure and 95% efficient masks (class N95 respirators) would be required, as is the case for pulmonary tuberculosis.2

Inhaled aerosols are not trapped by the mucociliary defenses of the respiratory tract and can penetrate to the periphery of the lung where they implant, proliferate, and become pathogenic. Indeed, from extensive autopsy data in the 1910-1911 Manchurian outbreak of pneumonic plague, the most common lesion was alveolitis, rather than involvement of the mucous membranes of the upper respiratory tract.3,4 Involvement of these airway sites, with secondary cervical buboes, would be expected if particles larger than 5 µ were inhaled and deposited on the sticky mucus stream moving over the upper respiratory tract and larger airways to the oropharynx. These sites have been noted occasionally to be infected in other outbreaks of pneumonic plague5; they are routinely infected if plague bacilli are implanted in the oral cavity of experimental animals, whereas primary plague pneumonia develops if the bacilli are injected directly into the trachea.2,5 Both droplet and aerosol transmission in several outbreaks of pneumonic plague have occurred; large particles that are inhaled are likely to lodge in the upper respiratory tract and produce tonsillar plague, whereas droplet nuclei tend to lodge in the lung and give rise to primary plague pneumonia.5

To prevent the spread of an almost uniformly fatal disease like primary plague pneumonia, it seems prudent to apply the more stringent standard of care, eg, use of well-ventilated rooms with negative pressure for housing patients and class N95 respirators by health care workers. To strengthen US preparedness against bioterrorism, we must rethink existing recommendations to ensure an adequate response to potential public health disasters.

Inglesby  TVDennis  DTHenderson  DA  et al.  Plague as a biological weapon: medical and public health management.  JAMA. 2000;283:2281-2290.Google Scholar
Garner  JSfor the Hospital Infection Control Practices Advisory Committee, Guidelines for isolation precautions in hospitals. Available at: http://aepo-xdv-www.epo.cdc.gov/wonder/prevguid/p0000419/entire.htm. Accessed August 23, 2000.
Strong  RP Report of the International Plague Conference. Manila, Philippines: Bureau of Printing; 1912.
Chernin  E Richard Pearson Strong and the Manchurian epidemic of pneumonic plague, 1910-1911.  J Hist Med Allied Sci. 1989;44:296-319.Google Scholar
Meyer  KF Pneumonic plague.  Bacteriol Rev. 1961;25:249-261.Google Scholar