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lymphadenitis involving a node draining the site of
inoculation. Most commonly, the primary site is inguinal,
although axillary or cervical nodes may be involved. The
involved nodes are swollen and tender, becoming fluctuant and
necrotic. Bubonic plague may progress spontaneously to the
septicemic form, which may then produce CNS or (less
frequently) pneumonic disease. Onset of primary septicemic
plague is similar, but without localizing "bubo". Infection by
flea bite or other cutaneous inoculation would most likely
produce bubonic or primary septicemic disease in most
individuals. In primary pneumonic plague, the incubation
period is shorter (1-6 days). Progressive respiratory
insufficiency, bloody sputum, and toxemia are typical.
Patients with pneumonia are highly contagious and should be
kept in respiratory isolation. Although some patients with
bubonic or septicemic plague may develop secondary pneumonia as
the disease process evolves, large numbers of individuals with
plague pneumonia almost certainly would indicate inhalation of
organisms delivered via aerosol.


DIAGNOSIS


Routing Laboratory Findings. Examination of bubo
aspirate, sputum, or cerebrospinal fluid by gram stain will
reveal numerous organisms typical morphologically of
Yersinia pestis.

Differential Diagnosis. Bubonic plague should be
suspected in large numbers of individuals with similar
findings of fever, malaise, and tender lymphadenopathy. An
epidemic of pneumonic plague in its early stages could be
confused with tularemia, anthrax~, or SEB; continued
deterioration without stabilization effectively rules out
SEB, while gram stain of the sputum, culture, and presence
of the plague F1 antigen in blood specimens provide more
specific evidence of plague.

Specific Laboratory Diagnosis. Yersinia pestis can be
readily cultured from blood, sputum, and bubo aspirates.
Presumptive diagnosis can be made by gram stain and (if
available) immunofluroscent staining. Most naturally
occurring strains of Y. pestis an "F1" antigen in-vivo,
which can be detected in serum samples by immunoassays
available in field diagnosis laboratories.

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