Human Cases of Black Plague Hits Four States
Pastor Dale Morgan
Human Cases of Black Plague Hits Four States*
largest number of US cases since 1994
October 13, 2006
JAMA
Plague is a zoonotic disease caused by the bacterium Yersinia
pestis. In 2006, a total of 13 human plague cases have been reported
among residents of four states: New Mexico (seven cases), Colorado
(three cases), California (two cases), and Texas (one case).
This is the largest number of cases reported in a single year in the
United States since 1994. Dates of illness onset ranged from February 16
to August 14; two (15%) cases were fatal. The median age of patients was
43 years (range: 13-79 years); eight (62%) patients were female. Five
(38%) patients had primary septicemic plague, and the remaining eight
(62%) had bubonic plague. Two (15%) patients developed secondary plague
pneumonia, leading to administration of antibiotic prophylaxis to their
health-care providers. This report summarizes six of the 13 cases,
highlighting the severity and diverse clinical presentations of plague
and underscoring the need for prompt diagnosis and treatment when plague
is suspected.
Case 1
On February 17, a man aged 39 years from Travis County, Texas, was
hospitalized with a 1-day history of high fever, delirium, nausea, and
vomiting. Although lymphadenopathy was not detected on the initial
examination, a prominent axillary bubo was noted later. Blood cultures
yielded Y. pestis. The patient recovered after treatment with multiple
antibiotics, including gentamicin, doxycycline, ciprofloxacin, and
levofloxacin. Before his illness, the patient had hunted rabbits in Lea
County, New Mexico, and skinned the rabbit carcasses. Cultures from one
of the carcasses yielded Y. pestis that was indistinguishable from the
clinical isolates when subtyped by pulsed-field gel electrophoresis (PFGE).
Case 2
On April 17, a woman aged 28 years received the first diagnosis of
plague in Los Angeles County, California, since 1984. The woman was
hospitalized with fever, septic shock, and a painful right axillary
swelling; blood cultures grew Y. pestis. She responded to treatment with
gentamicin and levofloxacin. Although symptoms were compatible with
bubonic plague, the diagnosis had not been suspected because the patient
did not report traveling outside her urban Los Angeles neighborhood.
Later, health-care providers learned that the patient had handled raw
meat from a rabbit that had been killed in Kern County, California, and
transported to her home. An environmental investigation in Kern County
revealed evidence of die-off among jackrabbits and cottontails; rabbit
carcasses collected in the area yielded Y. pestis. PFGE patterns of
isolates from the patient and rabbits were indistinguishable. A total of
16 medical contacts and family members and friends who had visited the
patient's residence received antibiotic prophylaxis.
Case 3
On May 17, a woman aged 54 years from Bernalillo County, New Mexico,
went to a local urgent care center with a 4-day history of fever, severe
abdominal pain, and bloody stools. No lymphadenopathy was noted. While
being evaluated, the patient began vomiting blood and experienced acute
respiratory distress. She was transferred to a regional hospital but
died within a few hours of arrival. Blood and lung cultures obtained at
autopsy yielded Y. pestis; however, no histologic evidence of plague
pneumonia was discovered. One of the patient's dogs and a rock squirrel
(Spermophilus variegatus) that had been trapped by investigators on her
property had serologic evidence of past infection with Y. pestis.
Case 4
On May 25, a man aged 45 years from Santa Fe County, New Mexico,
went to a hospital emergency department with a 3-day history of nausea,
vomiting, and fever to 104蚌 (40蚓). Initial chest radiographs revealed
right lower lobe infiltrates; he was admitted with a diagnosis of
pneumonia. The patient was treated with gentamicin but was not placed in
respiratory isolation. On hospital day 1, the patient required
intubation for respiratory distress. On hospital day 2, blood cultures
drawn at admission yielded Y. pestis. The patient remained on mechanical
ventilation for 4 weeks and eventually recovered. At least 37 hospital
workers who had contact with the patient before he was intubated
received postexposure prophylaxis with doxycycline. Both of the
patient's dogs had serologic evidence of past Y. pestis infection. Y.
pestis was isolated from fleas (Anomiopsyllus nudatus) combed from a
woodrat (Neotoma micropus) that was trapped by investigators on the
patient's property.
Case 5
On July 9, a man aged 30 years from La Plata County, Colorado, went
to a hospital emergency department with a 3-day history of fever,
nausea, vomiting, and right inguinal lymphadenopathy. He was discharged
home without treatment. Three days later, the man returned and was
hospitalized with sepsis and bilateral pulmonary infiltrates. Plague was
considered immediately, and the patient was placed in respiratory
isolation. He was treated with gentamicin and recovered. Five hospital
workers were administered doxycycline prophylaxis because of exposures
before respiratory isolation had been initiated. Cultures of blood and a
lymph node aspirate grew Y. pestis. One of the patient's dogs had
serologic evidence of past Y. pestis infection. Y. pestis was recovered
from fleas of two species (Aetheca wagneri and Pulex simulans) collected
near the patient's home. A plague epizootic had been noted in the area,
and four other human plague cases have been reported from La Plata
County since July 2005.
Case 6
On July 18, a woman aged 43 years from Torrance County, New Mexico,
went to a local clinic with a 1-day history of vomiting, diarrhea,
abdominal pain, and fever. The patient reported a recent dog bite and
was treated for presumed cellulitis. The next day, the woman returned to
the clinic because of worsening symptoms and pain in the left side of
her groin. She was transported by ambulance to the emergency department,
where inguinal lymphadenopathy was noted and plague was suspected. She
was admitted to the hospital, placed in the intensive care unit, and
administered gentamicin and doxycycline. Y. pestis was isolated from
blood cultures. Despite treatment, she died on July 22. Animals trapped
on the patient's property, including four mice (Peromyscus spp.) and
five rock squirrels, did not have laboratory evidence of infection with
Y. pestis.
Reported by:
L Bertram-Sosa, C Jaso, A Valadez, MD, Austin/Travis County Health
and Human Svcs Dept; B Nix, DVM, R Jones, MPH, T Sidwa, DVM, J Walker,
MD, Texas Dept of State Health Svcs. A Anglim, MD, Univ of Southern
California; R Reporter, MD, L Mascola, MD, G Van Gordon, MS, J Ramirez,
Los Angeles County Dept of Health Svcs; C Fritz, DVM, R Davis, ScD,
California Dept of Health Svcs. J Ross, MD, K Chongsiriwatana, MD,
Infectious Diseases and Internal Medicine Associates of New Mexico; M
DiMenna, PhD, J Sheyka, MS, City of Albuquerque Environmental Health
Dept; P Ettestad, DVM, C Smelser, MD, N Powers, PhD, P Reynolds, New
Mexico Dept of Health. J Fowler, San Juan Basin Health Dept, Durango; J
Pape, D Tanda, Colorado Dept of Public Health and Environment. P Mead,
MD, K Griffith, MD, KL Gage, PhD, J Montenieri, G Dietrich, MS, K
Kubota, MPH, J Young, Div of Vector-Borne Infectious Diseases, National
Center for Zoonotic, Vector-Borne, and Enteric Diseases (proposed); LH
Gould, PhD, EIS Officer, CDC.
CDC Editorial Note:
The natural reservoir of plague is wild rodents. Human infection
usually is acquired through the bites of infected rodent fleas and has
an incubation period of 1-6 days.1 Plague also can be contracted from
handling infected animals, especially rodents, lagomorphs (e.g., rabbits
or hares), and domestic cats, or through close contact with patients
with pneumonic plague. However, person-to-person transmission is
extremely rare; the last such transmission in the United States was
reported in 1925. During 1990-2005, a total of 107 cases of plague were
reported in the United States (CDC, unpublished data, 2006), a median of
seven cases per year. The increased plague activity in 2006 is
consistent with the predicted relationship between climate and the
frequency of human plague in the southwestern United States. Two
consecutive February-March periods with high precipitation and an
intervening cool summer predicts increased cases of plague the next
summer; this effect is thought to lead to increased reproduction and
survival rates among rodents and fleas.2
The principal forms of plague are bubonic, septicemic, and
pneumonic.3 All of these forms can be accompanied by fever and systemic
manifestations of gram-negative sepsis. Bubonic plague is distinguished
by the presence of a bubo (i.e., one or more enlarged, tender, regional
lymph nodes). Patients with septicemic plague often have prominent
gastrointestinal symptoms, including nausea, vomiting, diarrhea, and
abdominal pain,4 and patients with pneumonic plague have dyspnea, chest
pain, and a cough that can produce bloody sputum. During 1990-2005, a
total of 81 (76%) of 107 plague cases in the United States were
classified as primary bubonic plague, 19 (18%) as primary septicemic
plague, and five (5%) as primary pneumonic plague; two (2%) were not
classified (CDC, unpublished data, 2006). Eleven (10%) cases were fatal.
In 2006, five (38%) of the 13 patients had primary septicemic plague,
underscoring the need for clinicians to consider this diagnosis in
patients who do not have an obvious bubo. Septicemic and pneumonic
plague progress rapidly and are usually fatal without prompt treatment;
bubonic plague has a mortality rate of 50%-60% if untreated.
In the United States, nearly all fatal plague cases are associated
with delays in diagnosis and treatment. In its early stages, plague is
treatable with appropriate antibiotics. Health-care providers should
consider a diagnosis of plague in persons who (1) have unexplained
fever, suspected sepsis, or pneumonia with or without lymphadenopathy or
a classic bubo, and (2) live in or have traveled to a plague-endemic
region (e.g., the western United States).3 When plague is suspected,
appropriate antibiotic treatment should be initiated immediately and not
delayed for laboratory confirmation. Drugs effective against plague
include streptomycin and the tetracyclines. Although not approved by the
Food and Drug Administration (FDA) for treatment of plague, gentamicin
is more readily available than streptomycin and has been used
successfully.5 Fluoroquinolones are used empirically to treat critically
ill patients and have demonstrated activity against Y. pestis but are
not FDA approved for this indication.6
The majority of exposures to plague occur in the peridomestic
environment3; free-roaming pets that bring infected rodent fleas into
the home have been suspected as a potential source of human infections.
Persons residing in areas where plague is endemic should keep their dogs
and cats free of fleas through regular use of flea treatments and by
keeping them indoors. Year-round rodent control should be conducted,
including rodent proofing of structures and eliminating food sources
(e.g., pet food or garbage) and harborage (e.g., piles of wood or
debris) in the peridomestic environment. Persons who participate in
outdoor recreational activities, particularly rabbit hunting,7 in areas
of epizootic plague activity also are at risk for plague. Personal
protective measures include using insect repellents, wearing protective
clothing, and avoiding sick or dead animals. In areas of epizootic
plague activity, public health officials should treat rodent habitats
with insecticides and should educate the public regarding plague
prevention and control. Health-care providers and veterinarians should
be educated regarding the manifestations and diagnosis of plague.
Antibiotic prophylaxis might be indicated for close contacts (who come
within 2 m) of patients with plague pneumonia.5 Appropriate respiratory
droplet precautions should be taken when treating patients with
suspected plague who have evidence of respiratory involvement.8
Acknowledgments
This report is based, in part, on contributions by D Gardner, MD, R
Irvine, MD, S Lathrop, DVM, Univ of New Mexico Health Sciences Center,
Office of the Medical Investigator. R Eisen, PhD, R Vera-Tudela, X
Liang, A Janusz, Div of Vector-Borne Infectious Diseases, National
Center for Zoonotic, Vector-Borne, and Enteric Diseases (proposed), CDC.
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