Pathology of inhalational anthrax in 42 cases from the Sverdlovsk outbreak of 1979.

Abstract

A large epidemic of anthrax that occurred in Sverdlovsk (now Ekaterinburg), Russia, in 1979 resulted in the deaths of many persons. A series of 42 necropsies, representing a majority of the fatalities from this outbreak, consistently revealed pathologic lesions diagnostic of inhalational anthrax, namely hemorrhagic necrosis of the thoracic lymph nodes in the lymphatic drainage of the lungs and hemorrhagic mediastinitis. Bacillus anthracis was recovered in bacterial cultures of 20 cases, and organisms were detected microscopically in the infected tissues of nearly all of the cases. A novel observation was primary focal hemorrhagic necrotizing pneumonia at the apparent portal of entry in 11 cases. Mesenteric lymphadenitis occurred in only 9 cases. This remarkably large series demonstrated the full range of effects of anthrax bacteremia and toxemia (edema especially adjacent to sites of extensive infection and pleural effusions) and hematogenously disseminated infection [hemorrhagic meningitis (21 cases) and multiple gastrointestinal submucosal hemorrhagic lesions (39 cases)].

Full text

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Proc. Natl. Acad. Sci. USA
Vol. 90, pp. 2291-2294, March 1993
Medical Sciences
Pathology of inhalational anthrax in 42 cases from the Sverdlovsk
outbreak of 1979
(Bacillus anthracis/hemorrhagic mediastinitis/hemorrhagic thoracic lymphadenitis/epidemic/Russia)
FAINA A. ABRAMOVA*, LEV M. GRINBERGt, OLGA V. YAMPOLSKAYAt, AND DAVID H. WALKER§1
*Department of Pathology, Hospital 40, Ekaterinburg, Russia; tDepartment of Pathoanatomy, Tuberculosis and Pulmonary Diseases Unit, Ekaterinburg,
Russia; tDepartment of Infectious Diseases, Central Postgraduate Institute, Botkin Hospital, Moscow,Russia;and §Department of Pathology, University of
Texas Medical Branch, Galveston, TX 77555-0609
Communicated by Matthew Meselson, December 14, 1992
ABSTRACT
Sverdlovsk (now Ekaterinburg), Russia, in 1979 resulted in the
deaths ofmany persons. A series of42 necropsies, representing
a majority of the fatalities from this outbreak, consistently
revealed pathologic lesions diagnostic of inhalational anthrax,
namely hemorrhagic necrosis ofthe thoracic lymph nodes in the
lymphatic drainage ofthe lungs and hemorrhagic mediastinitis.
Bacillusanthraciswas recovered inbacterialcultures of20cases,
and organisms were detected microscopically in the infected
tissuesofnearly allofthecases. A novelobservation wasprimary
focal hemorrhagic necrotizingpneumonia attheapparent portal
of entry in 11 cases. Mesenteric lymphadenitis occurred in only
9 cases. This remarkably large series demonstrated the full
range of effects of anthrax bacteremia and toxemia (edema
especially adjacent to sites of extensive infection and pleural
effusions) and hematogenously disseminated infection [hemor-
rhagic meningitis (21 cases) and multiple gastrointestinal sub-
mucosal hemorrhagic lesions (39 cases)].
A large epidemic of anthrax that occurred in
Beginning early in April 1979, there was a sudden outbreak
of an unknown disease among the population of Sverdlovsk
in the former Union of Soviet Socialist Republics. In this
large industrial city just east of the Ural Mountains, the
majority of the patients resided in a limited area on the
southern edge of the municipality. International interest was
drawn by the suspicion that the epidemic might have resulted
from release ofabiologic agentfrom a military facility located
in the district where the majority of the patients lived. A
publication in May 1980 attributed the epidemic to cutaneous
and gastrointestinal exposure to meat from animals infected
with Bacillus anthracis (1).
Little further information has been published. In fact, the
hospital records of the patients affected by this outbreak
including the autopsy reports wereremoved from the hospital.
Notes describing the details of the gross observations in the
organs at the autopsies of 42 persons in this epidemic were
kept in the personal possession of two of the participating
pathologists (F.A.A. and L.M.G.). The microscopic slides,
paraffin blocks, and tissue samples from the necropsies were
also kept in a secure location. A substantial collection of
representative examples of the diseased organs was also
maintained for demonstration. A series of detailed articles on
the macroscopic lesions, microscopic lesions, and causes of
death will be published in the Russian medical literature (2).
This preliminary report has the purpose of providing in the
English language the major observations in a timely manner.
MATERIALS AND METHODS
During the period of 1 week in June 1992, the four authors
reexamined together the glass microscopic slides and the
available gross organs and evaluated the correlations with
notes made in 1979 ofthe gross descriptions ofeach necropsy
and the microscopic observations for that case. Cultures had
been taken for identification of bacterial agents. Bacteria
were searched for microscopically in sections stained with
hematoxylin and eosin in all cases. Sections cut from six
blocks were stained by the Brown-Brenn and Brown-Hopps
methods for demonstration of Gram-positive and Gram-
negative bacteria (3, 4).
RESULTS
The initial diagnosis of anthrax was made by the pathologist
(F.A.A.) in case 1 ofthis series on the basis ofthe remarkably
hemorrhagic meningitis in a patient who died on approxi-
mately the sixth day of the epidemic. The diagnosis was
confirmed by demonstration of bacilli on smears prepared at
necropsy on the same day (April 10, 1979) and definitively
documented by identification of B. anthracis in cultures on
April 11.
This series of 42 autopsies represents a striking illness
affecting previously healthy persons, who died usually after
a rapid course of 1-4 days duration (Table 1). All 42 cases
were characterized by the most prominent and consistent
lesions ofhemorrhagic thoracic lymphadenitis (Figs. 1-3) and
hemorrhagic mediastinitis (Figs. 3 and 4). Spread of B.
anthracis to the peribronchial lymph nodes by the lymphatic
vessels was emphasized by the presence of the organisms in
the marginal sinus where the afferent lymph first enters the
lymph node (Fig. 5). The pulmonary portal of entry was
further emphasized by the presence of a primary anthrax
pulmonary focus-i.e., focal hemorrhagic, necrotizing an-
thrax pneumonia in 11 patients.
There were various manifestations of hematogenous
spread of B. anthracis infection including serohemorrhagic
and hemorrhagic leptomeningitis (21 cases) (Figs. 6 and 7).
Gastrointestinal lesions were observed in 39 cases, most of
which appeared to represent multifocal hematogenous spread
ofB. anthracis to the submucosa ofthe gastrointestinal tract,
in particular to the small intestine, stomach, and colon (Figs.
8 and 9). The lesions did not involve the Peyer's patches.
Mesenteric lymph nodes demonstrated hemorrhagicinvolve-
ment in only 9 cases.
A remarkable effect of the disease was edema and other
evidence of increased vascular permeability including gelat-
inous edema of the mediastinum, pleural effusions, lepto-
meningeal edema, and pulmonary edema. B. anthracis was
observed in the lesions of serohemorrhagic nature, and
anthrax toxins secreted by these organismswere considered
to be the cause of the vascular damage resultingin hemor-
rhage and serious exudate.
ITo whom reprint requests should be addressed.
2291
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2292
Medical Sciences: Abramova et al.
Table 1.
Sverdlovsk in 1979
Forty-two patients with inhalational anthrax in
B.
anthracis
identifi-
cation
Cul-
Date
Admis-
sion
4/10
4/8
4/9
4/8
Pathology
Age/
sex
42/M
67/M
68/F
38/M
47/M
68/M
25/F
66/F
50/M
65/M
48/M
42/M
40/M
52/M
37/M
32/M
52/M
68/F
71/F
58/F
42/F
49/M
43/M
68/F
44/M
39/M
46/M
50/F
45/M
39/M
42/M
42/M
48/M
33/M
32/M
55/M
33/M
43/M
25/M
30/M
29/M
¶/M
Onset
4/7
4/7
4/8
4/9
4/10
4/10
4/12
4/10
4/11
4/12
4/10
4/13
4/15
1
4/14
4/14
4/15
4/15
4/15
4/17
4/20
4/21
4/21
4/22
4/25
4/27
4/29
5/4
5/7
5/9
5/12
4/12
4/13
4/13
4/13
4/13
4/13
4/13
4/13
4/14
4/16
4/13
4/16
4/15
4/22
4/21
4/23
4/24
4/28
5/1
4/30
5/6
5/12
5/15
Death ture
4/10
4/9
4/10
4/8
4/12
4/13
4/13
4/13
4/13
4/14
4/14
4/14
4/14
4/14
4/15
4/15
4/16
4/16
4/15
4/25
4/17
4/16
4/16
4/30
4/18
4/19
4/21
4/25
4/22
4/23
4/24
4/24
4/24
5/3
4/28
5/1
4/30
5/10
5/12
5/10
5/16
11
+
§
+
§
+
-
+
+
-
-
-
+
+
+
-
-
-
-
-
-
-
+
-
-
+
+
+
-
-
+
-
+
+
-
+
-
+
-
+
+
-
+
Hist- HEM HEM
ology LN* MEDt
++
¶
+
++
§
+
+
+
+
+
+
+
++
+
+
+
+
++
+
+
++
+
+
+
+
++
+
+
¶
,+
+
+
_
+
+
+
+
+
++
_
+
+
+
+
+
+
+
++
+
+
+
+
++
+
+
+
+
¶
+
+
+
++
++
¶
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
MEN*
+
+
+
+
+
+
+
§
*Hemorrhagic thoracic lymphadenitis.
tHemorrhagic mediastinitis.
tSerohemorrhagic and hemorrhagic meningitis.
§Not examined.
$Unknown.
IFound dead and autopsied on 6/15, with preservation oftissues and
condition ofthe body suggesting a short interval between death and
necropsy.
DISCUSSION
The pattern of lesions in these 42 cases of fatal anthrax
bacteremia and toxemia from Sverdlovsk is typical of inha-
lational anthrax in experimentally infected nonhuman pri-
mates (5) and in epidemiologically diagnosed humans (6-13).
The pathogenesis ofB. anthracis infection that enters via the
normal lung begins with transport of spores to the peribron-
chial and mediastinal lymph nodes (8, 14). After germination
of the spores, the bacteria replicate and secrete the three
FIG. 1.
nodes in case 41 reveals massive hemorrhagic enlargement of the
peribronchial and carinal lymph nodes with extension of the hem-
orrhage into the adjacent tissues including the submucosa of the
bronchi and trachea.
The cut surface of the lungs, trachea, and hilar lymph
components of the toxin: protective antigen, edema factor,
and lethal factor (15-17). Thus, inhalational anthrax is char-
acterized by the severe local effects ofthe toxin at its primary
site of production, thoracic hemorrhagic necrotizing lym-
phadenitis and hemorrhagic necrotizing mediastinitis, as well
as the systemic effects of bacteremia and toxemia. These
thoracic lesions are not expected to occur in toxemic cuta-
neous or intestinal anthrax because spread from the cutane-
ous or intestinal portal of entry by the lymphatic vessels
would involve the regional lymphatic drainage ofthe primary
skin or intestinal lesion, but there would be no spread to the
lymphatic drainage of the lungs in the mediastinum. In 11
cases of the present series, there was a single primary
pulmonary lesion analogous to the Ghon focus in the more
slowly developing infection, tuberculosis.
The gastrointestinal lesions appear to be mainly, or pos-
sibly wholly, hematogenous in origin. The lesions are cen-
FIG. 2.
39 reveals marked dilation of the marginal and draining sinuses
because of the presence of protein-rich edema and hemorrhage.
(Hematoxylin-eosin stain; x90.)
Photomicrograph of a peribronchial lymph node of case
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
-
-
Proc. Natl. Acad Sci. USA 90(1993)

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Proc. Natl. Acad. Sci. USA 90 (1993)
*,:,''.-.i.:.>.__>'>:S^...........................
FIG. 3.
rhage and necrosis and adjacent hemorrhagic mediastinitis in case 39.
(Hematoxyhineosin stain, x25.) (Inset) Higher magnification pho-
tomicrograph of the same section demonstrates lymph node necrosis
with karyorrhectic debnis, macrophages containing anthracotic pig-
ment, and B. anthracis organisms. (Brown-Brenn stain; X375.)
Photomicrograph of a thoracic lymph node with hemor-
tered in the submucosa where the blood supply is most
prominent. These lesions are analogous to the submucosal
metastases of hematogenously disseminated highly malig-
nant neoplasms. The mucosa was present over even the
largest hemorrhagic lesions that in some cases extended
through the muscularis propria, further suggesting that the
infection amrved in the submucosa via the bloodstream rather
than entering the mucosa from the gastrointestinal lumen. In
fact, Gram-positive bacilli were observed microscopically in
blood vessels of the intestinal submucosa. In 4 of the 11
reported cases of the pathology of fatal inhalational anthrax
published in the English language since 1960, intestinal
lesions presumably of hematogenous origin were described
(6, 7, 9, 10-13). Moreover, the classic Russian pathology text
by Davidovsky (18) emphasizes that in 90% of cases with
gastrointestinal lesions, the enteric pathology occurs because
of hematogenous spread of bacilli from a cutaneous or
respiratory portal of entry. Although a study ofthe pathology
of epidemiologically diagnosed intestinal anthrax is lacking,
the best data available suggest that the primary lesion of
intestinal anthrax is usually solitary and located in the
terminal ileum or cecum (19). The lesions in the present series
of cases usually were numerous and involved many regions
of the gastrointestinal tract, including in most cases the
stomach and jejunum, indicating that the gastrointestinal
MM,
"A~~~~~~~~~~4
T~
FIG 3
Phtmcorp
of a thoaci lymp
.
no*dXewth emr
with~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.
kayrhci
men, an
tere
in th
sumcs
deri, marohae cotiig ath,racotic...
. anthaci oraim. (Bron-Ben
wherel th
stain
suppl'-is'! most' '
I35
b,.loo.. ,d
prmnet Thes
metastases of heaoenul
nant neplsm.Th
lagst heorhai
''"e,s"...,", ns are anloou
to thsubmcosa
disseminated hihymlg
wa
preen
over. even the
tha
in som
case
muos
leson
exene
FIG. 4.
thracis in a hemorrhagic area of the mediastinum of case 39.
(Brown-Brenn stain; x375.)
Photomicrograph of a cluster of Gram-positive B. an-
.
4,W4'
d
FIG. 5.
lymph node in case 39 that is distended by lymph and contains many
B. anthracis organisms, some ofwhich appear Gram-positive (dark)
while others appear Gram-negative (lighter bacilli and filaments).
(Brown-Hopps stain; x250.)
Photomicrograph of the marginal sinus of a thoracic
involvement was most likely hematogenous. In 9 of our
cases, the route of spread from the pulmonary portal ofentry
included lymphogenous spread to the mediastinal lymph
nodes, followed by hematogenous spread to the intestinal
wall and subsequent lymphatic spread to the mesenteric
lymph nodes, which were less severely involved than the
thoracic lymph nodes. Unfortunately, there is a paucity of
information regarding the pathology and pathogenesis of
primary intestinal anthrax for comparison with our cases
(18-26).
The tragedy of these deaths is compounded by the condi-
tions of secrecy that have impeded elucidation ofmany facts
that potentially would be useful in the future diagnosis and
treatment of inhalational anthrax. The paucity of clinical
information impairs extensive clinicopathologic correlations
including the effects of various therapeutic approaches.
Some deaths occurred outside the hospital, at home, or even
in the street or in a field. Medical personnel accompanying
the emergency transport vehicles often made an initial diag-
FIG. 6.
edly hemorrhagic leptomeninges. (Hematoxylin-eosin stain; xlS.)
Photomicrograph of the brain from case 41 shows mark-
2293
Medical Sciences: Abramova et al.

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2294
Medical Sciences: Abramova et al.
>O..g
~~
M~
.
.,*,
*
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r
.
4~~~~~ V.i.',,'a f vSs ':"S
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114
FIG. 7.
many B. anthracis organisms and marked hemorrhage. (Brown-
Hopps stain; x210.)
Photomicrograph ofthe leptomeninges of case 41 reveals
nosis of pneumonia. The chest pain, which was severe
enough to suggest an initial diagnosis of myocardial infarc-
tion, undoubtedly resulted from the hemorrhagic thoracic
lymphadenitis and mediastinitis.
Previous reports ofthe cases in this outbreak have excluded
description of the thoracic pathology (1). The availability of
these new data leads to the conclusion that these patients died
because of inhalation of aerosols containing B. anthracis.
Description ofcases ofcutaneous anthrax suggests that some,
if not all, might have been acquired from animals infected by
the same source of spore-containing aerosol. None of these
cases of cutaneous anthrax, which is usually not fatal, were
represented in this large autopsy series.
We thank Ms. Wendy DuPriest for secretarial assistance in the
preparation of the manuscript. This investigation was supported in
part by a grant from the John D. and Catherine T. MacArthur
Foundation to Matthew Meselson for a continuing study of the
Sverdlovsk anthrax epidemic of 1979.
FIG. 8.
(Left) Photomicrograph of a substantial focus of submu.
cosal hemorrhage in the small intestine that extends into the mus-
cularis propria
in
case
6. The overlying
(Hematoxylin-eosin stain;
x13.) (Right) The
intestinal hemorrhage contains B.
Hopps stain; x250.)
mucosa
is
still
visible.
area of submucosal
anthracis organisms. (Brown-
FIG. 9.
of case 6 shows small blood vessels that contain B. anthracis
organisms. (Brown-Hopps stain; x300.)
Photomicrograph ofthe submucosa ofthe small intestine
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