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be confused with a wide variety of viral, bacterial, and
fungal infectious diseases. Progression over 2-3 days with
the sudden development of severe respiratory distress
followed by shock and death in 24-36 hours in essentially
all untreated cases eliminates diagnoses other than
inhalation anthrax. The presence of a widened mediastinum
on chest X-ray, in particular, should alert one to the
diagnosis. Other suggestive findings include chest-wall
edema, hemorrhagic pleural effusions, and hemorrhagic
meningitis. Other diagnoses to consider include aerosol
exposure to SEB; but in this case, onset would be more rapid
after exposure (if known), and no prodrome would be evident
prior to onset of severe respiratory symptoms. Mediastinal
widening on chest X-ray will also be absent. Patients with
plague or tularemia pneumonia will have pulmonary
infiltrates and clinical signs of pneumonia (usually absent
in anthrax).

Specific Laboratory Diagnosis. Bacillus anthracis will
be readily detecable by blood culture with routine media.
Smears and cultures of pleural fluid and abnormal
cerebrospinal fluid may also be positive. Impression smears
of mediastinal lymph nodes and spleen from fatal cases
should be positive. Toxemia is sufficient to permit anthrax
toxin detection in blood by immunoassays, and such assays
will be available in field-deployed laboratories (see
Section III).

Therapy. Almost all cases of inhalation anthrax where
treatment was begun after patients were symptomatic have been
fatal, regardless of treatment. Historically, penicillin has
been regarded as the treatment of choice, with 2 million units
given intravenously every 2 hours. Tetracycline and
erythromycin have been recommended in penicillin-sensitive
patients. The vast majority of anthrax strains are sensitive
in vitro to penicillin. However, penicillin-resistant strains
exist naturally, and one has been recovered from a fatal human
case. Moreover, it is not difficult to induce resistance to
penicillin, tetracycline, erythromycin, and many other
antibiotics through laboratory manipulation of organisms. All
naturally-occurring strains tested to date have been sensitive
to erythromycin, chloramphenical, gentamicin, and
ciprofloxacin. In the current setting, treatment should be
instituted at the earliest sign of disease with ciprofloxacin

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