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Bioterrorism-Related Anthrax
Opening a Bacillus
anthracis–Containing Envelope, Capitol Hill, Washington, D.C.:
The Public Health Response
Vincent P. Hsu,* Susan L. Lukacs,* Thomas Handzel,* James Hayslett,*
Scott Harper,* Thomas Hales,* Vera A. Semenova,* Sandra Romero-Steiner,*
Cheryl Elie,* Conrad P. Quinn,* Rima Khabbaz,* Ali S. Khan,* Gregory
Martin,† John Eisold,‡ Anne Schuchat,* and Rana A. Hajjeh*
*Centers for Disease Control and Prevention, Atlanta, Georgia,
USA; †National Naval Medical Center, Bethesda, Maryland, USA; and
‡Office of the Attending Physician, U.S. Capitol, Washington, D.C.,
USA
Suggested citation for this article: Hsu
VP, Lukacs SL, Handzel T, Hayslett J, Harper S, Hales T, et al.
Opening a Bacillus anthracis-containing envelope, Capitol
Hill, Washington, D.C.: the public health response. Emerg Infect
Dis [serial online] 2002 Oct [date cited];8. Available
from: URL: http://www.cdc.gov/ncidod/EID/vol8no10/02-0332.htm
On October
15, 2001, a U.S. Senate staff member opened an envelope containing
Bacillus anthracis spores. Chemoprophylaxis was promptly
initiated and nasal swabs obtained for all persons in the immediate
area. An epidemiologic investigation was conducted to define exposure
areas and identify persons who should receive prolonged chemoprophylaxis,
based on their exposure risk. Persons immediately exposed to B.
anthracis spores were interviewed; records were reviewed to
identify additional persons in this area. Persons with positive
nasal swabs had repeat swabs and serial serologic evaluation to
measure antibodies to B. anthracis protective antigen (anti-PA).
A total of 625 persons were identified as requiring prolonged
chemoprophylaxis; 28 had positive nasal swabs. Repeat nasal swabs
were negative at 7 days; none had developed anti-PA antibodies
by 42 days after exposure. Early nasal swab testing is a useful
epidemiologic tool to assess risk of exposure to aerosolized B.
anthracis. Early, wide chemoprophylaxis may have averted an
outbreak of anthrax in this population.
In the fall of 2001, a series of envelopes containing Bacillus
anthracis spores were sent via the U.S. Postal Service (USPS)
to cities in Florida and New York. Consequently, many persons, including
staff on Capitol Hill, received training on how to respond to suspicious
envelopes that might contain B. anthracis spores. This training
was based on previously prepared recommendations for a comprehensive
response to biological attacks using B. anthracis (1–3).
On October 15, 2001, an envelope addressed to Senator Tom Daschle
containing B. anthracis spores was opened by one of his staff
members. While the bioterrorism events in Florida and New York came
to the attention of public health authorities only when persons
were diagnosed (4–7) with anthrax, the
event on Capitol Hill was different—the presence of B. anthracis
spores was suspected immediately, allowing appropriate response
and prompt initiation of chemoprophylaxis in exposed persons. A
known source of exposure allowed a rapid epidemiologic investigation,
using nasal swab cultures for B. anthracis, environmental
sampling, and serologic testing. Although previous epidemiologic
studies have used nasal swabs and serologic tests to assess B.
anthracis exposure and subclinical (asymptomatic) infection
in endemic and outbreak settings (8–11),
the usefulness of these tools in the context of a bioterrorism event
is not known.
We describe here the initial public health response to the opening
of the contaminated envelope on Capitol Hill and the epidemiologic
methods used to determine the exposed area and the population at
risk for developing anthrax. While the public health response later
included the letter traceback through the entire postal system,
including identification and prophylaxis of at-risk USPS employees
(12), we limit our discussion to Capitol Hill.
The results and epidemiologic importance of environmental sampling
for B. anthracis, although briefly mentioned, will be the
focus of a separate paper.
Timeline
of Events
On October 15, 2001, at 9:45 a.m., a staff member on the 6th floor
of the Hart Senate Office Building (HSOB) in the office of Senate
Majority Leader Tom Daschle cut open a taped business envelope containing
a letter and a powdery substance (Table 1).
Upon noticing a burst of dust, she placed the letter on the floor
and notified the U.S. Capitol Police. Within 5 minutes of being
notified, officers were at the scene. The hazardous device unit
of the Capitol Police arrived minutes later. The officers and emergency
response personnel, referred to as first responders, arrived with
respiratory personal protective equipment (PPE) on hand, but equipment
was not put on until after arrival at the scene. These officers
tested the powder for B. anthracis spores twice, using commercial
rapid tests. Preliminary results obtained within 15 minutes suggested
that the powder contained B. anthracis. Laboratories at the
U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID)
in Fort Detrick, Maryland, later confirmed these preliminary results.
At approximately 10:30 a.m., the ventilation system was shut off.
Medical staff from the Office of the Attending Physician (OAP),
U.S. Capitol, began collecting nasal swabs for B. anthracis
culture from staff members in Senator Daschle’s office, from staff
in an adjacent office belonging to Senator Russell Feingold, and
from the first responders; in addition, an initial 3-day antimicrobial
postexposure prophylaxis regimen consisting of ciprofloxacin, 500
mg twice a day, was given to these persons. Only the person who
opened the contaminated envelope removed and changed her clothing
and was decontaminated with soap and water. All others washed their
hands with soap and water.
Next, first responders led employees from the two 6th-floor offices
to the 9th floor of the building, where further samples were taken
from nares and clothing. After testing, these employees were led
back to Senator Daschle’s 5th-floor office, where other staff members
were detained. At approximately 3:00 p.m., the staff members
were allowed to go home.
Employees in other offices continued working until the close of
business. The southwest quadrant of the building was closed the
morning of October 16, and a decision was made to close the entire
HSOB that evening. During the next 3 days, OAP continued to collect
nasal swabs for B. anthracis for all HSOB employees present
on October 15 and for others on Capitol Hill who requested these
tests. OAP also gave those tested an initial 3-day antimicrobial
prophylaxis, pending final confirmation of the presence of B.
anthracis spores and results of the epidemiologic investigation.
Methods
A team from the Centers for Disease Control and Prevention (CDC)
arrived in Washington D.C., on the morning of October 16 to begin
the epidemiologic investigation. To identify the group of persons
who needed prolonged antimicrobial prophylaxis on the basis of likely
exposure to B. anthracis spores, we sought to define an exposure
area of higher risk.
To identify other facilities that may have been contaminated with
B. anthracis spores, the contaminated envelope was traced
back through the congressional mail distribution system before its
arrival in Senator Daschle’s office. To define the exposure area
for HSOB, we obtained floor diagrams for the 5th and 6th floors
and information about the ventilation system from the Office of
the Architect of the Capitol, which maintains and operates the U.S.
Capitol complex. Multiple environmental samples were taken
from these facilities by a variety of techniques (13).
The population at risk of developing anthrax was defined as persons
in the exposed area during or after the time the contaminated envelope
was processed or opened. To identify each person who may have been
within the exposure area, employee lists were obtained from staff
managers for each affected facility; in HSOB, managers for individual
senators’ offices within the defined exposure area were contacted
to obtain employee and visitor lists. We identified responders within
HSOB, such as law enforcement and medical personnel, by contacting
supervisors for a comprehensive list of those who were in the area.
To identify other visitors or nonemployees, press conferences were
used to relay the appropriate information.
Within 9 hours of the initial event, nasal swab specimens were
collected for all persons in Senator Daschle’s and Senator Feingold’s
offices and for all first responders. As mentioned earlier, further
specimens were collected by OAP, for 4 days after the opening of
the contaminated envelope, from employees of HSOB and others
on Capitol Hill. Specimens were collected with Dacron fiber-tipped
sterile swabs and sent for B. anthracis culture at the National
Naval Medical Center in Bethesda, Maryland. Persons with initial
positive nasal swabs for B. anthracis had repeat nasal swabs
at 7 days postexposure and were administered a questionnaire about
symptoms consistent with anthrax disease. In addition, serum specimens
were obtained from these persons and tested at the CDC Meningitis
and Special Pathogens Laboratory for the presence of immunoglobulin
(Ig) G antibodies to B. anthracis protective antigen (anti-PA)
at 7, 21, and 42 days postexposure.
In collaboration with OAP, efforts were made to ensure that all
exposed persons were contacted and that they received appropriate
prophylaxis with ciprofloxacin, or in the cases of persons unable
to tolerate a quinolone, with doxycyline. OAP closely monitored
persons who came to the clinic with respiratory symptoms; follow-up
surveys were later conducted on persons receiving long-term antibiotic
prophylaxis.
Results
Defining the Exposure
Area and Population at Risk
Within Capitol Hill, the traceback of the contaminated envelope
before its arrival in Senator Daschle’s office showed that it had
been screened through a mail facility on P Street and then through
the Senate nonpublic mailroom, located in the Dirksen Senate Office
Building (Table 2). Nasal swabs for B.
anthracis in employees of both mail facilities were negative;
however, since exposure to B. anthracis spores may have occurred
during mail handling of the contaminated letter, the Dirksen mailroom
and the entire P Street facility, which was an open warehouse, were
defined as exposed areas. Additionally, positive environmental samples
for B. anthracis were found in the mailroom in the Ford House
Office Building, where mail to the House of Representatives is processed.
Although the contaminated envelope did not pass through the Ford
Building mailroom, the potential of aerosolization of spores from
processing equipment, as well as the possibility of an additional
contaminated envelope, warranted its designation as an exposed area.
Senator Daschle’s suite is located on the 5th and 6th floors of
the southeast quadrant, with an open internal staircase joining
the floors. An adjacent suite occupied by staff of Senator Feingold
has a similar layout. Both adjacent offices share a common hallway
that serves as the main entry to the 6th-floor office, but no door
connects the Daschle and Feingold suites. A single ventilation system
supplies and exhausts air for the nine floors in the southeast quadrant,
independently of other areas in the building.
In HSOB, where the primary release of B. anthracis spores
occurred, all persons with nasal cultures positive for B. anthracis
were clustered in and around Senator Daschle’s office and were
located on either the 5th or 6th floor (see below). Preliminary
environmental sampling results were positive for B. anthracis
spores from within the same rooms occupied by persons with
positive nasal cultures. The location of the contaminated office
was within the shared ventilation space of the southeast quadrant
of the building. The exposure area in HSOB was thus defined as the
southeast quadrant of the 5th and 6th floors. Within these four
designated exposure areas (5th- and 6th-floor southeast quadrant,
P Street facility, and the Dirksen and Ford Building mailrooms),
625 persons were identified as employees, visitors, or otherwise
being within the exposed areas (Table 2).
More than 2,000 persons received an initial 3-day course of antibiotics,
but only the 625 persons from the defined exposure areas were recommended
to receive 60 days of chemoprophylaxis.
Nasal Swabs Results
OAP obtained nasal swabs for B. anthracis culture from
2,172 persons during October 15–October 18, including the 625 persons
identified at risk. Of these, 71 were known to be in the immediate
exposure area within the first hour of the event in which the contaminated
envelope was opened (Table 3); 65 were Senate
staff, and 6 were first responders. A total of 28 persons had positive
nasal cultures for B. anthracis; all positive results were
from specimens obtained on October 15 between 10:30 a.m. and 7:00
p.m. The median age of these persons was 27 years (range 21–57).
All persons positive for B. anthracis entered either Senator
Daschle’s or Senator Feingold’s suites, with the exception of one
responder who was in the hallway adjacent to Senator Daschle’s office
on the 6th floor but did not enter either suite. All 18 persons
(including 5 first responders) in Senator Daschle’s 6th-floor suite
had positive nasal cultures; a much lower proportion had positive
nasal swabs on the 5th-floor Daschle suite (28%) and 6th-floor Feingold
suite (13%).
Repeat nasal swabs from the 28 persons with initially positive
nasal cultures for B. anthracis were negative for all persons
at 7 days postexposure. Serologic tests were negative for anti-PA
IgG antibodies in all persons at 7, 21, and 42 days after exposure.
To date, anthrax has not developed in anyone in this cohort or in
the larger cohort of persons on Capitol Hill.
Discussion
Among the series of bioterrorism incidents during 2001 related
to B. anthracis–contaminated envelopes, this event was unique
because it was the first with a known source of exposure, enabling
a rapid public health response by a multidisciplinary team including
law enforcement officers, medical and public health personnel, laboratory
personnel, industrial hygienists, and engineers. The known source
enabled us to assess the usefulness of nasal swab cultures in determining
exposure to B. anthracis.
The contaminated letter purportedly contained about 2 g of powder,
with each gram reported to contain between 100 billion to 1 trillion
spores (14). The recovery of B. anthracis
from nasal cultures was limited to persons who were inside Senator
Daschle or Feingold’s offices or in the hallway joining the two
offices. Nasal swab results suggest that the ventilation system
played a very small role, if any, in the spread of anthrax spores
in HSOB. Based on proportions of persons with positive nasal swabs,
most dissemination likely occurred through room currents from the
6th to the 5th floor of the Daschle suite via an open staircase;
closed doors that blocked air currents were most likely the reason
a smaller proportion in Senator Feingold’s office had positive nasal
cultures despite being adjacent to Senator Daschle’s office.
Swabs were taken within 1 day of the initial event from all 71
persons in the immediate exposure area, including those with positive
nasal cultures for B. anthracis. However, in others with
negative results, testing was not done for up to 4 days. Although
these persons were located outside the immediate exposure area,
it is uncertain whether prompt antibiotic administration, a delay
in nasal swab testing, or both, may have had an effect on those
nasal culture results. In one animal model involving macaques, large
inhaled doses of anthrax spores in a controlled setting yielded
B. anthracis in nasal swabs of all animals within 24 hours
of exposure, and although sensitivity decreased as time progressed,
positive nasal cultures were recovered in some macaques 1 week after
exposure (15). In the Florida anthrax investigation,
positive nasal cultures were detected in a person >1 week after
presumed exposure (5). Repeat swabs from the persons
with initially positive cultures were negative at 7 days postexposure,
but prophylaxis administration may have influenced those results.
The greatest sensitivity for recovery of B. anthracis can
be achieved by obtaining nasal swab specimens as early as possible
after recognized exposure.
Nasal swabs served as an epidemiologic tool; we considered the
work locations of those with positive nasal swabs to be areas at
risk for anthrax exposure. However, interpretation of positive or
negative nasal swab results for individual risk assessment of anthrax
disease has not been evaluated, and nasal swabs should not be used
for this purpose. In the case of one person who died after exposure
to anthrax, a nasal swab culture was negative (16).
Likewise, environmental sampling may be a valuable component of
assessment of areas of risk, but individual environmental samples
are not sufficient to determine a person's risk for anthrax.
Two other issues deserve mention. First, the use of PPE may be
an effective barrier to exposure to B. anthracis spores,
although its efficacy could not be addressed in this investigation;
no responder entering Senator Daschle’s office wore PPE before entering
the office, and all had positive nasal swabs. Second, while subclinical
anthrax infection has been documented in persons with continuous
exposure to B. anthracis spores (9), the
lack of serologic conversion in persons with positive nasal cultures
suggests that no apparent asymptomatic infection occurred during
this event, when prophylaxis was promptly initiated and continued.
Since the initial events of October 15, more information has become
available—four cases of inhalational anthrax, two of them fatal,
occurred in USPS employees from the Washington, D.C., Postal Distribution
Center where Senator Daschle’s envelope was sorted (7,12,16),
and a fifth case occurred in an employee of another mail facility,
which receives government mail from the Washington, D.C., Distribution
Center. These events led to new recommendations to expand the traceback
for future events through the entire path to envelope origin. In
addition, updated prophylaxis and treatment protocols, including
options for vaccination, and subsequent recommendations for a comprehensive
response to a bioterrorism attack involving B. anthracis
have been published (17–21). In Table
4, specific recommendations are given for a comprehensive public
health response and epidemiologic investigation that prevent further
spread, identify and treat those at risk, and avoid mass administration
of prolonged prophylaxis to persons not considered at risk for anthrax
in the event of a future bioterrorist attack.
In conclusion, a rapid and coordinated public health response helped
avert an anthrax outbreak by identifying and administering prophylaxis
to persons at high risk for disease. Nasal swabs can provide useful
information about the extent of exposure to B. anthracis
spores to assist with defining groups at risk.
Epidemiologic assessment of risk for anthrax in persons in settings
affected by a biological attack is complex, and much remains to
be learned. In the meantime, a well-developed public health infrastructure,
effective antimicrobial prophylaxis strategies, and effective guidelines
for management based on past experiences are essential in our defense
against future bioterrorism events.
Acknowledgments
We thank Patrick McConnon from the Centers for Disease Control
and Prevention (CDC) for coordinating communication on Capitol Hill,
all other members of the CDC Washington, D.C., Anthrax Response
Team [1] who assisted
in the Capitol Hill investigation (including epidemiology and laboratory
personnel at CDC and in Washington, D.C.), and employees of the
Washington, D.C,. Health Department. We also thank all employees
of the Office of the Attending Physician, U.S. Capitol staff, National
Naval Medical Center staff, and U.S. Capitol employees, especially
U.S. Senate staff and U.S. Capitol Police, for their assistance
during this unprecedented event.
Dr. Hsu is an Epidemic Intelligence Service officer with the Respiratory
and Enteric Virus Branch at the Centers for Disease Control and
Prevention. His main research interests involve infectious diseases
of a global nature, specifically research on tuberculosis, HIV,
and rotavirus infections.
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[1] Members of the CDC Washington, D.C., Anthrax
Response Team: Alicia Anderson, Tracy Agerton , Mary-Kate Appicelli,
Paul Arguin, Robert Benson, Lilah Besser, Richard Besser, John Brooks,
John Cardinelly, George Carlone, Mei Castor, Gerald Curtis, Lisa
Delaney, Peter Dull, Eric Esswein, Cindy Friedman, Kate Glynn, Ron
Hall, Rick Hartle, Leigh Ann Hawley, Leta Helsel, Tami Hilger, Patricia
Holder, Scott Johnson, Molly Kellum, Bradley King, Jonathan King,
Maria Elena Jefferds, Jill Levine, Han Li, Ken Martinez, Dino Mattorano,
Jane McCamon, Trudy Messmer, Elizabeth Mothershed, Andy Mullins,
Minday Perilla, Janet Pruckler, Julia Rhodes, Daniel Schmidt, Stephanie
Schwartz, Theresa Smith, Karen Stamey, Evelene Steward-Clark, Eyasu
Teshale, Lanier Thacker, Tim Uyeki, and Brad Winterton.
September 19, 2002. The following names were inadvertently
omitted from the list above: Laura Broyles, Catherine Dentinger,
Puneet Dewan, Alicia Fry, Cindy Hamlin, Debbie Hurlburt, Dennis
Kim, Kayla Laserson, Mark Long, Kelly Moore, Stephanie Schrag, Andi
Shane, Bruce Tierney, Kevin Winthrop. We regret this omission.
| Table
1. Timeline of events within the Hart Senate Office Building,
Washington, D.C., October 15, 2001a |
|
|
Time of day
|
Event /response
|
|
|
9:45 a.m.
|
Staff person opens letter containing Bacillus
anthracis spores
|
|
9:55 a.m.
|
First responders arrive at scene
|
|
10:00 a.m.
|
Hazardous device unit arrives at scene and
performs initial tests for B. anthracis
|
|
10:15 a.m.
|
First rapid test is positive for B. anthracis
|
|
10:30 a.m.
|
Ventilation system turned off
Second rapid test is positive
OAPb begins nasal swab testing and antibiotic chemoprophylaxis
distribution
|
|
10:40 a.m.
|
6th floor staff moved to 9th floor; swabbing
continues; staff later moved to 5th floor
|
|
3:00 p.m.
|
Senators Daschle and Feingold’s staff allowed
to go home
|
|
|
aOne responder with a positive
nasal swab who was in the 6th-floor hallway did not enter
the Daschle or Feingold suites and was not included in this
table.
bOAP, Office of the Attending Physician.
|
|
