Page 119 - Journal of Special Operations Medicine - Summer 2015

An Ongoing Series

Q Fever

Mark W. Burnett, MD

ABSTRACT

Q fever is a zoonotic disease found throughout the Figure 1 Electron microscopic scan of the bacterium.
world. It is caused by the intracellular gram-negative
bacterium Coxiella burnetii. Infection by C. burnetii oc-
curs primarily by inhalation of the aerosolized bacteria
from birthing animals or contaminated dust. The bacte-
rium is very resistant to drying and heat, and is consid-
ered highly endemic in the Middle East, where it is likely
underdiagnosed. Special Operations Forces medical pro-
viders should be aware of this disease, which must be in
the differential diagnosis of a patient who has a history
of fever, elevated liver enzymes, pneumonia in its acute
form, and endocarditis, especially in those with existing
valvular heart disease in its chronic form.
Source: From the Centers for Disease Control and Prevention: http://
Keywords: Q fever; disease, zoonotic phil.cdc.gov/phil/home.asp.

or by blood transfusion. A single inhaled organism can
cause disease; therefore, this bacterium is a biological
Background
hazard and has been weaponized with varying degrees
Q fever, short for “query fever,” was a name proposed in of success.
the late 1930s to describe the unknown cause of a febrile
illness seen in slaughterhouse workers in Brisbane, Aus- Clinical Presentation
tralia. Research efforts conducted in the United States
and Australia, led by Herald Rea Cox and Macfarlane It is unknown what percentage of those who are in-
Burnet, respectively, led to the discovery of the intracel- fected with C. burnetii are asymptomatic or have mild
lular species of bacterium that was named in their honor symptoms. The incubation period of those eventually
as Coxiella burnetii (Figure 1). Q fever infections have symptomatic with Q fever is 2 to 3 weeks. Fever oc-
been described on all continents except Antarctica. curs in virtually all of these patients, lasting a median of
10 days in large studies including those who were un-
Most commonly, humans are infected by either being in treated, although it may resolve within 72 hours in pa-
contact with infected domestic farm animals, primarily tients started on appropriate antibiotics. Other common
cattle, sheep, and goats, or soil that has been contami- findings in patients with acute Q fever include fatigue,
nated and inhaled. These animals shed the organism in chills, and intractable headaches. Nonspecific pneumo-
greatest numbers during the birth process, but also in nia on chest radiograph, as well as elevated transami-
their milk, urine, and feces. C. burnetii is an extremely nase levels with a normal leukocyte count are seen, as
hardy organism that can survive and remain infective is thrombocytopenia in some cases. Case-fatality rates
for years, even in very dry and hot environments. It has in previously healthy adults are thought to be less than
been shown to travel in dust for great distances. Inhal- 2%. Children are more likely to have milder symptoms,
ing the dust leads to infections in those who have had but may display a skin rash. Women who are infected
no contact with infected animals. Rarely, this illness has before conception or during their pregnancy are at risk
been transmitted to humans by person-to-person con- of miscarriage, stillbirth, delivering low–birth weight in-
tact, tick bite, ingestion of contaminated dairy products, fants, and preterm delivery.

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