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To the Editor: Dr Inglesby and colleagues¹ recommend that aerosol-generating autopsies (essentially all autopsies) performed on individuals who have died of plague should be conducted in negative-pressure rooms by prosectors wearing high-efficiency particulate air–filtered respirators. However, their recommendation points to a major limitation in our national autopsy infrastructure. Deaths from known bioterrorist events are classified as homicides and therefore fall under the jurisdiction of medical examiners and coroners, who would investigate these deaths and, unless overwhelmed by large numbers of fatalities, perform autopsies of the bodies. Similarly, medical examiners or coroners might also perform autopsies of individuals who die precipitously and unexpectedly from a covert bioterrorist attack.

Unfortunately, most offices of medical examiners and coroners and, indeed, most hospital autopsy facilities in the United States are inadequately constructed and ill prepared to perform autopsies that require respiratory precautions. Aerosol-transmitted outbreaks of tuberculosis have been traced to autopsies done in the Syracuse, NY, Medical Examiner's office, Los Angeles, Calif, Coroner's Office, University of Arkansas School of Medicine, and University of Health Sciences/Chicago Medical School.^2-5 These outbreaks were attributed to inadequate ventilation of autopsy rooms and insufficient respiratory precautions.

If autopsy prosectors and other office personnel are not adequately protected from the risks of tuberculosis, it is unlikely that they will be protected from the risk of plague. Many offices of medical examiners and coroners are located in older facilities, which often have common air circulation between prosecting areas and administrative spaces. Prosectors often do not adhere to guidelines intended to prevent the spread of blood-borne and aerosolized pathogens. To perform safe autopsies on bodies with infectious diseases, including those infectious diseases that may be a consequence of bioterrorism, we need an improved national autopsy infrastructure. Funding is needed to bring autopsy facilities into compliance with accepted public health standards and to provide prosectors with appropriate protective equipment. Prosectors will need to comply with recommended safety procedures. Because the infective potential of a body may be unknown, all autopsy-performing agencies consistently should be able to protect both prosectors and office personnel from aerosolized pathogens.

Kurt B. Nolte, MD
Office of the Medical Investigator
University of New Mexico School of Medicine
Albuquerque

1. Inglesby TV, Dennis DT, Henderson DA, et al. Plague as a biological weapon: medical and public health management. JAMA. 2000;283:2281-2290. FREE FULL TEXT 2. Kantor HS, Poblete R, Pusateri SL. Nosocomial transmission of tuberculosis from unsuspected disease. Am J Med. 1988;84:833-837. FULL TEXT | ISI | PUBMED 3. Meyer J. TB plagues office of LA Coroner. Los Angeles Times. April 25, 1997:A1, A27. 4. Templeton GL, Illing LA, Young L, Cave D, Stead WW, Bates JH. The risk for transmission of Mycobacterium tuberculosis at the bedside and during autopsy. Ann Intern Med. 1995;122:922-925. FREE FULL TEXT 5. Ussery XT, Bierman JA, Valway SE, Seitz TA, DiFernando GT Jr, Ostroff SM. Transmission of multidrug-resistant Mycobacterium tuberculosis among persons exposed in a medical examiner's office, New York. Infect Control Hosp Epidemiol. 1995;16:160-165. ISI | PUBMED

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.

Matthew E. Levison, MD
Division of Infectious Diseases
MCP Hahnemann University
Philadelphia, Pa

1. Inglesby TV, Dennis DT, Henderson DA, et al. Plague as a biological weapon: medical and public health management. JAMA. 2000;283:2281-2290. FREE FULL TEXT 2. Garner JS for 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. 3. Strong RP, ed. Report of the International Plague Conference. Manila, Philippines: Bureau of Printing; 1912. 4. Chernin E. Richard Pearson Strong and the Manchurian epidemic of pneumonic plague, 1910-1911. J Hist Med Allied Sci. 1989;44:296-319. FREE FULL TEXT 5. Meyer KF. Pneumonic plague. Bacteriol Rev. 1961;25:249-261. FREE FULL TEXT

In Reply: The authors from the Working Group for Civilian Biodefense share Dr Nolte's concerns about the potential limitations of the national autopsy infrastructure to prevent postmortem-associated acquisition of infection. As Nolte points out, guidelines regarding pathogens that might be aerosolized by postmortem procedures are of importance not only to protect against disease caused by biological weapons, but also to prevent the spread of naturally acquired infectious diseases.

Dr Levison proposes that infection control guidelines for patients with pneumonic plague should recommend negative pressure rooms for affected patients and class N95 respirators for health care workers. While data are limited and further research would be useful, there is no epidemiological evidence that pneumonic plague can be spread from person to person by droplet nuclei (aerosols). This is in contrast to pulmonary tuberculosis, for which there is clear evidence of contagion by droplet nuclei. Available evidence suggests that the risk of person-to-person spread of pneumonic plague is very low and that it requires respiratory droplet transmission by direct close (<2 m) contact.

The last US case of person-to-person spread of pneumonic plague was in a 1924 epidemic during which the disease was spread from 2 index patients to a number of close household contacts.¹ In the United States in the last 50 years, there have been 7 cases of primary pneumonic plague and 54 cases of pneumonic plague secondary to the bubonic or septicemic form of disease (Centers for Disease Control and Prevention [CDC], D.T.D., unpublished data, July 14, 2000). However, none of these cases resulted in plague being spread from person to person.²

In the Manchurian pneumonic plague epidemics of 1910-1911, investigators concluded that disease was spread by respiratory droplets and required close, direct contact with patients; furthermore, they concluded that the use of a simple gauze mask was effective in preventing spread from patients to health care workers.^{1, 3-4} Despite the continued sporadic occurrence of plague around the world, often in crowded urban settings, there has been a paucity of pneumonic plague outbreaks. There are no modern reports of pneumonic plague outbreaks in which more than 1 generation of pneumonic transmission has occurred.

There is no evidence to warrant the use of class N95 masks and negative pressure rooms to interrupt the secondary transmission of pneumonic plague. Moreover, recommending these procedures could lead to counterproductive logistical and cost issues. Class N95 masks are much more expensive than simple surgical masks and would require fit-testing before use. The number of negative pressure rooms in most hospitals is quite limited and adding a substantial number of such rooms would be very costly.

Because of these considerations and the other evidence presented in the working group consensus statement on the management of plague,⁵ the working group advises the use of simple surgical masks as part of respiratory droplet precautions to prevent person-to-person transmission of pneumonic plague. This recommendation is consistent with those of the CDC and the Association for Professionals in Infection Control and Epidemiology,² as well as that of the World Health Organization expert committee on plague.⁶

Thomas V. Inglesby, MD; Donald A. Henderson, MD, MPH; Tara O'Toole, MD, MPH
Center for Civilian Biodefense Studies
Johns Hopkins Schools of Medicine and Public Health
Baltimore, Md

David T. Dennis, MD, MPH
National Center for Infectious Diseases
Centers for Disease Control and Prevention
Fort Collins, Colo

1. Meyer K. Pneumonic plague. Bacteriol Rev. 1961;25:249-261. 2. Centers for Disease Control and Prevention. Fatal human plague. MMWR Morb Mortal Wkly Rep. 1997;278:380-382. 3. Chernin E. Richard Pearson Strong and the Manchurian epidemic of pneumonic plague, 1910-1911. J Hist Med Allied Sci. 1989;44:296-319. FREE FULL TEXT 4. Wu L-T. A Treatise on Pneumonic Plague. Geneva, Switzerland: League of Nations Health Organization; 1926. 5. Inglesby TV, Dennis DT, Henderson DA, et al. Plague as a biological weapon: medical and public health management. JAMA. 2000;283:2281-2290. FREE FULL TEXT 6. Dennis DT, Gage K, Gratz N, Poland J, Tikhomirov E. Plague Manual: Epidemiology, Distribution, Surveillance and Control. Geneva, Switzerland, World Health Organization; 1999. WHO/CDS/CSR/EDC/99.2, 58.

Letters Section Editors: Stephen J. Lurie, MD, PhD, Senior Editor; Phil B. Fontanarosa, MD, Executive Deputy Editor.

JAMA. 2000;284:1648-1649.

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Plague as a Biological Weapon: Medical and Public Health Management
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