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To the Editor: In their Consensus Statement on hemorrhagic fever viruses that may be used as biological weapons, Dr Borio and colleagues¹ state, "There are no reported cases of person-to-person or nosocomial spread of flaviviruses." At least 2 cases of nosocomial transmission of dengue (a flavivirus) have been reported in the medical literature: one through a needlestick injury² and the other through bone marrow transplantation.³ These events, although rare, suggest that nosocomial spread may also be possible for a more feared flavivirus—yellow fever.

José G. Rigau-Pérez, MD,MPH
Dengue Branch, Division of Vector-Borne Infectious Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
San Juan, Puerto Rico

1. Borio L, Inglesby T, Peters CJ, et al. Hemorrhagic fever viruses as biological weapons: medical and public health management. JAMA. 2002;287:2391-2405. FREE FULL TEXT 2. de Wazières B, Gil H, Vuitton DA, Dupond JL. Nosocomial transmission of dengue from a needlestick injury. Lancet. 1998;351:498. PUBMED 3. Rigau-Pérez JG, Vorndam AV, Clark GG. The dengue and dengue hemorrhagic fever epidemic in Puerto Rico, 1994-1995. Am J Trop Med Hyg. 2001;64:67-74. ABSTRACT

To the Editor: In their Consensus Statement, Dr Borio and colleagues¹ briefly mention Kyasanur Forest disease virus (KFDV), which occurs in a remote part of the world. In 1957, 2 of my colleagues and I were accidentally infected with KFDV while engaged in vaccine preparation.² Despite our adherence to all of the then-current laboratory precautions, including wearing a face mask, face shield, and gown and working in individual vented cubicles, emulsification of infected tissues created an aerosol that resulted in clinical illness. This incident is evidence that KFDV, although transmitted in nature by a tick bite, is indeed infectious as an aerosol.

Our effort (and risk) in 1957 was to prepare a vaccine to protect people living in the region of the Kyasanur Forest (India) from becoming infected. So, many years later, it is very sad that our current concern pertains to the potential peril of KFDV and similar viruses as agents of bioterrorism.

Leonard J. Morse, MD
Departments of Clinical Medicine and Family Medicine and Community Health
University of Massachusetts Medical School
Worcester

1. Borio L, Inglesby T, Peters CJ, et al. Hemorrhagic fever viruses as biologic weapons: medical and public health management. JAMA. 2002;287:2391-2405. FREE FULL TEXT 2. Morse LJ, Russ SB, Needy CF, Buescher EL. Studies of viruses of the tick borne encephalitis complex, II: disease and immune response in man following accidental infection with Kyasanur Forest disease virus. J Immunol. 1962;2:240-248.

In Reply: We agree with Dr Rigau-Pérez that transmission of dengue by needlestick injury and bone marrow transplantation is possible. We excluded dengue from our analysis for reasons we discussed in our article. Although cases of nosocomial transmission of yellow fever have not been reported, it would be prudent to assume that exposure to a viremic patient through needlestick injury or bone marrow transplantation could transmit infection.

In response to Dr Morse, we stated that all of the viruses we reviewed are "highly infectious in the laboratory setting and may be transmitted via small-particle aerosol," as exemplified by his own unfortunate experience. This is why these viruses are routinely handled only in biosafety level 4 laboratories. Such infectivity poses great problems for patient care in the event of an outbreak. We favor the use of point-of-care analyzers to process clinical specimens of patients at the bedside, thereby precluding the need for aerosol-generating procedures and exposure of laboratory workers. In the event that point-of-care analyzers are not available or feasible, we suggest additional precautions to reduce the risk of accidental infection of laboratory workers.

Luciana Borio, MD
Johns Hopkins Center for Civilian Biodefense Strategies
Johns Hopkins Schools of Medicine and Public Health
Baltimore, Md
Critical Care Medicine Department
Clinical Center
National Institutes of Health
Bethesda, Md

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2002;288:571.