Diagnosis
Diagnosis
of Q fever is difficult in mild cases because of a lack of symptoms. The most common symptoms include extreme
fever (104°F), headache, fatigue, muscle pain, vomiting, diarrhea,
non-productive cough, sweating, and chills.
The fever lasts 1-2 weeks, and significant weight loss is apparent. Thirty to fifty percent of patients with
symptomatic cases will develop pneumonia, and liver failure has also been
observed. Most cases resolve with a few
months without treatment, and only 1-2% of cases end in death.
The
incubation period depends on the number of bacteria contracted. A single bacterium can cause disease but
with a lengthy incubation time. Most
patients become ill within 2-3 weeks after exposure, and chronic disease may
occur 1-20 years post-exposure. Chronic Q fever can progress from the initial
infection and last more than 6 months.
Endocarditis often occurs in chronic cases.
Because
these symptoms are not exclusive to Q fever, serologic testing must be used to
confirm a diagnosis. Indirect
immunofluorescence assays (IFA), polymerase chain reactions (PCR),
enzyme-linked immunosorbant assay (ELISA) and immunohistochemistry (IHC) are
examples of common tests. IHC requires
a tissue sample, and is therefore most often used postmortem.
References:
*CDC: www.cdc.gov
*Texas Department of Health: http://www.tdh.state.tx.us/bioterrorism/facts/qfever.html