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Causative
Agent
Routes of Exposure
Infective Dose &
Infectivity
Incubation Period
Clinical Effects
Lethality
Transmissibility
Primary Contaminations & Methods of Dissemination
Secondary Contamination & Persistence of organism
Decontamination &
Isolation
Outbreak control
Laboratory testing
Therapeutic Treatment
Prophylactic Treatment
Differential Diagnosis
References
Causative
Agent:
Q fever is a zoonotic disease caused by a
rickettsia Coxiella burnetii.
Route of Exposure:
Humans usually acquire Q fever through the inhalation of
airborne particles. Sheep, cattle, and goats can serve
as reservoirs for the agent. Consumption of contaminated
food or water can also result in infection.
Infective Dose &
Infectivity: 1-10
Organisms
Incubation Period:
The incubation period ranges from 10 to 40 days.
Clinical Effects: Q
fever generally occurs as a self-limiting illness lasting 2
days to 2 weeks. The disease generally presents as an
acute non-differentiated febrile illness with headaches,
fatigue and myalgias as prominent symptoms. Pneumonia with an
abnormal chest X-ray occurs in about 50% of all patients.
Non-productive cough and pleuritic chest pain can also occur.
Uncommon complications of Q fever infection include: chronic
hepatitis, endocarditis, aseptic meningitis, encephalitis, and
osteomyelitis.
Lethality:
While highly
incapacitating, the death rate due to Q fever is very low
(<1-3%).
Transmissibility (person to
person): Transmission from person-to-person is extremely
rare.
Primary Contamination & Methods of Dissemination:
The most likely route of intentional
dissemination would be through aerosolization.
Alternatively, the organism could be disseminated through
sabotage of the food supply.
Secondary Contamination & Persistence of Organism:
Persons who are exposed to Q fever through the aerosol route
do not present a risk for secondary contamination or re-aerosolization
of the organism. The organism is highly resistant to
many disinfectants.
Decontamination &
Isolation:
-
Patients
– Patients can be treated using standard precautions.
Gross decontamination is not necessary.
-
Equipment
& other objects
– Contaminated surfaces and clothing can be decontaminated
with 0. 5% hypochlorite solution (one part household bleach
and nine parts water = 0.5% solution) or a 1:100 solution of
Lysol.
Outbreak control:
Since secondary cases are unlikely, outbreak control measures
are not recommended.
Laboratory Testing: Isolation of C. burnetii is usually not
done due to the risk to laboratory workers. Diagnosis
can be made acute and convalescent antibody titers (indirect
immunofluorescence antibody or complement fixation antibody),
polymerase chain reaction on tissue, or positive
immunostaining on a heart valve.
Therapeutic Treatment: Tetracycline or doxycycline is the recommended
treatment. A combination of erythromycin plus rifampin
is also effective.
Prophylactic Treatment: Treatment with a tetracycline during the
incubation period may delay, but will not prevent the onset of
symptoms. A vaccine has been developed, but is not
licensed for use in the United States.
Differential Diagnosis: Q fever must be differentiated from pneumonias
caused by mycoplasma, Legionella pneumophila,
Chlamydophila psittaci, or Chlamydophila pneumoniae.
References:
-
Committee
on Infectious Diseases. Q Fever. In: Pickering LK, ed. Red
Book: 2003 Report of the Committee on Infectious Diseases.
Elk Grove Village, IL: American Academy of Pediatrics; 2003:
512-514.
-
Chin J.
Control of Communicable Diseases Manual, Seventeenth
Edition, American Public Health Association; 2000.
-
Kortepeter
M, Christopher G, Cieslak T, et al. Medical Management of
Biological Casualties Handbook, U.S. Army Medical Research
Institute of Infectious Diseases, U.S. Department of
Defense; 2001: 33-36.
-
Byrne WR.
Q Fever. In: Zajtchuk R, Bellamy RF, eds. Medical Aspects of
Chemical and Biological Warfare. Washington, DC: Office of
the Surgeon General, U.S. Department of the Army; 1997:
523-537.
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