2. History & Significance
14th Century: “Black Death” responsible for
>20 million deaths in Europe
Used as a BW agent by Japan in WW II
Studied by Soviet and, to a smaller
extent, U.S. BW programs
1995: Larry Wayne Harris arrested for illicit
procurement of culture via mail
3. Epidemiology
Caused by Yersinia pestis
Gram negative, non-motile, non-spore-forming bacillus
Resistant to freezing temperature and drying, killed by
heat and sunlight
Zoonotic infection; Humans are accidental hosts
Human plague occurs from bite of an infected flea
(bubonic)
Outbreaks are cyclical corresponding to rodent reservoir
and arthropod vector populations
Only pneumonic form of plague is spread person-to-
person
Last case of person-to-person transmission in U.S.
occurred in 1924
4. Epidemiology
Transmission
Historically, rat-borne urban epidemics
Now mostly endemic sylvatic plague with sporadic
outbreaks
Pneumonic is only form capable of person to person
spread
Higher risk in overcrowding, indoor
contacts, cold/wet weather
5. Epidemiology
Risk Factors
Close contact with case
Contact with infected animal
Living or recent travel in endemic area
Peridomestic animals running loose
Residing in crowded conditions
Cool, wet weather
Exposure to a known intentional release
6. History of Plague
Plague recorded more than 2000 years ago
Three pandemics
1st 542AD; 100million dead in 60 years; from N.Africa
2nd 14th century; Black Death; 25million dead in Europe
alone (>1/4 of entire population); from central Asia;
disease became endemic in urban rat population and
smaller epidemics occurred through 17th century
3rd ended in 1990s; Burma to China (1894) & Hong Kong
to other continents including N. America via rat-infected
ships; 20million dead in India alone; foci of infection firmly
established in wild rodents in rural areas
About 10-15 cases/year U.S.
7. Epidemiology cycles
Sylvatic (wild) Cycle of Plague
Reservoir (foci) = wild rodents (prairie
dogs, rabbits, mice, dogs)
Vector = wild rodent flea
Urban (domestic) Cycle of Plague
Reservoir = domestic (urban) black rat
Over 8 million in NYC = human population
Vector = oriental rat flea (Xenopsylla cheopis)
Human Cycle of Plague
Bubonic plague acquired from contact with either
sylvatic or urban reservoirs or arthropod vector bite
and further transmitted in human population by
spread of pneumonic plague
9. Plague
Case Definition
Characterized by
fever, chills, headache, malaise, prostration,
& leukocytosis that manifests in one or more
of the following clinical forms:
Regional lymphadenitis (bubonic)
Septicemia w/o evident bubo (septicemic)
Plague pneumonia
Pharyngitis & cervical lymphadenitis (pharyngeal)
10. Plague
Case Definition, cont.
Laboratory criteria for diagnosis:
Presumptive
Elevated serum antibody titers to Y. pestis F1 antigen (w/o
documented 4-fold change) in a patient with no history of plague
vaccination OR
Detection of F1 antigen in a clinical specimen by fluorescent assay
Confirmatory
Isolation of Y. pestis from a clinical specimen OR
4-fold or greater change in serum antibody titer to Y. pestis F1
antigen
11. Plague: Case Classification
Suspected: Clinically compatible case w/o
presumptive or confirmatory lab results
Probable: Clinically compatible case with
presumptive lab results
Confirmed: Clinically compatible case with
confirmatory lab results
12. Plague
Clinical Forms
Bubonic plague
Most common naturally-occurring form
Mortality 60% untreated, <5% treated
Primary or secondary septicemic
plague
Pneumonic plague
Most likely BT presentation
From aerosol or septicemic spread to lungs
Survival unlikely if treatment not initiated w/in 24
hours of the onset of symptoms
13. Bubonic Plague
Incubation: 2-8 days
Sudden onset nonspecific symptoms:
fever, chills, malaise, muscle aches, headache
Regional lymphadenitis (buboes)
Swollen, very painful lymph nodes
Typically inguinal, femoral, axillary, or cervical
Erythema overlying skin
May have surrounding edema
Concurrent with or shortly after onset of other symptoms
15. Pneumonic Plague
Clinical Presentation
Incubation: 1-6 days (usually 2-4 days)
Acute onset of fever with cough, dyspnea, and
chest pain
Hemoptysis characteristic; watery or purulent
sputum also possible
Prominent GI symptoms may be
present, including
nausea, vomiting, diarrhea, and abdominal
pain
Other symptoms include
headache, chills, malaise, myalgias
16. Surveillance
Any clinical or laboratory suspicion of
plague cases should be immediately
reported to the local health department
and laboratory and if applicable the
hospital epidemiologist or infection
control practitioner
17. Prevention
Vaccination - Bubonic only
Killed virulent strain – used in U.S.
Formalin-fixed, no longer commercially
available
Future production and licensure unknown
Series
3 primary (1.0cc, 0.2 cc at 1-3 mo and 5-6
mo later)
2 boosters 0.2cc at 6 mo intervals then q1-
2yrs
18. Prevention
Vaccination
Indications
Lab workers with fully virulent strains
Military personnel stationed in endemic
areas
Efficacy
Based on WWII (0 cases) and Vietnam (3
cases) troops
Protects vs. bubonic only, not pneumonic
Adverse effects
Significant number have mild reactions
19. Prevention
Vaccination
Indications
Lab workers with fully virulent strains
Military personnel stationed in endemic areas
Efficacy
Based on WWII (0 cases) and Vietnam (3 cases)
troops
Protects vs. bubonic only, not pneumonic
Adverse effects
Significant number have mild reactions
May be severe
20. Infection Control
Mechanism for person-person spread
Not completely understood
Respiratory droplets most likely, not droplet nuclei
Historically prevented by masks
Respiratory Droplet Precautions
Wear mask, gown, gloves, eye protection
Suspected cases - isolate
Immediately respiratory (even for bubonic)
Avoid unnecessary close contact 1st 48 hrs of abx
Duration
2 days after initiating antibiotics and clinically improved
After sputum cultures negative
21. Infection Control
Respiratory Droplet Precautions
Mask during transport
Can cohort if not enough room
Contacts – consider isolation
Recommended for those receiving
PEP
during1st 48 hrs of Rx
Not recommended for those
refusing PEP Image: National Library of Medicine
22. Infection Control
Standard Precautions
Successfully treated cases after 48hr
of abx
Laboratory safety
Alert lab if suspected
BSL-2 for normal procedures
BSL-3 if hi risk aerosolizing or large
volumes or resistant strains
23. Infection Control
Corpses
Standard strict precautions by
trained personnel
Transport same as live patient
Avoid aerosolizing procedures or
use HEPA filters and negative
pressure room
24. Infection Control
National control programs
Surveillance
Early diagnosis, treatment &
isolation of cases
Environmental sanitation &
exposure avoidance
Public education
Non-eradicable
25. Decontamination
Environment
Aerosol dispersed within an hour –
fragile
No evidence residual bacteria are a
threat
No environmental decon indicated
May need surveillance measures for
rodents/fleas in area
26. Decontamination
Patient rooms
Usual cleaning
Use standard precautions
Disinfect contaminated linens
Standard disinfectants
27. Post-exposure Prophylaxis
Also for mass causalities
For all asymptomatic contacts of suspected
untreated pneumonic cases
Contact within last 6 days
Untreated pneumonic = <48hr approp treatment
Those within 2 meters of case
Household, hospital contacts
Those who might have been exposed to initial
aerosol
Seek out homeless, mental
handicaps, homebound
28. Post-exposure Prophylaxis
Antibiotics
1st choices
Tetracyclines
Doxycycline
o 100 po bid adults and kids >45 kg
o 2.2 mg/kg po bid for kids <45 kg
Tetracycline – equivalent dosages
Fluoroquinolones
Ciprofloxacin
o 500 mg po bid for adults
o 20 mg/kg po bid (max 1g/day) for kids
Others at equivalent dosages
29. Post-exposure Prophylaxis
Alternatives
Chloramphenical 25 mg/kg po qid
Not in kids <2yo
For pregnant & breastfeeding women
Same as adults above but no tetracycline
Doxycycline may be used
Duration
7 days since last exposure PEP
10 days for mass casualties
