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Commentary
Syndromic Surveillance in
Bioterrorist Attacks
Arnold F. Kaufmann,* Nicki T. Pesik,* and Martin I. Meltzer*
*Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Suggested
citation for this article
The article by Nordin et al. (1) in this issue of Emerging
Infectious Diseases describes the use of syndromic surveillance to detect
inhalational anthrax resulting from a hypothetical covert release of Bacillus
anthracis spores at a major shopping mall. This study is an important
evaluation of syndromic surveillance's utility in detecting an inhalational
anthrax epidemic against a background of real patient presentations. Based
on historical clinical data from a large health maintenance organization
(HMO), the authors evaluated the sensitivity of a syndromic surveillance
system to detect an incident by season of the year, day of the week when
the release occurred, and attack rate in mall patrons.
Although numbers of persons exposed and becoming ill, as modeled in the
study, are not specified, the effect can be inferred from the specified
methods. On the basis of information from the mall's Web site (2)
and the methods stated in the article, the number of cases associated
with a 15% attack rate in mall visitors (115,000 daily average) and workers
(12,000) would be ≈19,000 (if no additional exposures occurred after
day of release). Of these patients, 59% would be from the metropolitan
area in which the mall was located, an additional 6% would reside within
a 150-mile radius of the metropolitan area, and the remainder would be
from more distant points, including international visitors. Syndromic
surveillance, with the HMO patient database, would detect 50% of such
incidents by day 5, with only 20% detected by day 4. Lesser attack rates
would notably lower the probability of detection. Even more problematic,
the syndromic surveillance systems, as modeled, would fail to detect the
outbreak in 13% of releases in summer and 47% of releases in winter. Performance
would improve markedly with higher attack rates. After detection of an
aberrant signal, the occurrence of a syndrome must be investigated to
determine the cause, and exposure history of patients must be determined
to discover the source. These investigations could result in additional
delay before a targeted response could be mounted to prevent more illnesses.
Such delays are problematic because the effectiveness of postexposure
prophylaxis for inhalational anthrax is related to speed of implementation
(3).
The authors point out that an astute clinician might diagnose inhalational
anthrax in a patient before syndromic surveillance detected that an outbreak
of some type was occurring. If, as the 15% attack rate scenario suggests,
>100 patients had onset of illness on day 2 after exposure,
a correct diagnosis could be established for at least 1 patient by day
4. By this time, hundreds of inhalational anthrax patients would be seen
at hospitals, at least 1 day before the syndromic surveillance system,
as modeled, would have a 50% probability of signaling the outbreak.
The issue now becomes whether or not syndromic surveillance can augment
the public health response to an outbreak. For example, if a syndromic
surveillance system allowed follow-up of individual cases, it might accelerate
case finding and investigation into the source of infection. This potential
role of syndromic surveillance was not included in the modeled scenario.
Syndromic surveillance systems, of the type modeled by Nordin et al.,
may be too slow to allow public health officials and policy makers to
mount a sufficiently rapid postexposure prophylaxis campaign. Therefore,
the ability of many current syndromic surveillance systems to rapidly
detect bioterrorist attacks needs to be improved. Another reason to improve
syndromic surveillance systems is that the systems may have public health
value other than detecting bioterrorist attacks, such as tracking the
course of seasonal diseases. We should not forget, however, that clinical
care providers will continue to have a critical role in detecting bioterrorist
attacks, and communications must be maintained with these first-line sentinels.
Dr Kaufmann is a
senior service fellow in the Environmental Public Health Readiness Branch,
Division of Emergency and Environmental Health Services, National Center
for Environmental Health, Centers for Disease Control and Prevention.
His research interests are preparedness and response to bioterrorism,
particularly Bacillus anthracis–related events.
References
- Nordin JD, Goodman MJ, Kulldorff M, Ritzwoller DP,
Abrams AM, Kleinman K, et al. Simulated anthrax attacks and syndromic
surveillance. Emerg Infect Dis. 2005;11:1396–400.
- Mall of America: media: mall facts [homepage on the Internet]. [cited
2005 Jul 14]. Available from http://www.mallofamerica.com/about_the_mall/mallfacts.aspx
- Kaufmann AF, Meltzer MI, Schmid GP. The
economic impact of a bioterrorist attack: are prevention and postattack
intervention programs justifiable? Emerg Infect Dis. 1997;3:83–94.
Suggested citation
for this article:
Kaufmann AF, Pesik
NT, Meltzer MI. Syndromic surveillance in bioterrorist attacks. Emerg
Infect Dis [serial on the Internet]. 2005 Sep [date cited]. Available
from http://www.cdc.gov/ncidod/EID/vol11no09/05-0981.htm
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