Q Fever: Symptoms, Diagnosis, and Comprehensive Patient Guide

Q fever is a bacterial disease that can affect humans and various animals, especially cattle, sheep, and goats. The “Q” stands for “Query,” reflecting its mysterious origins when first identified in Australia in 1935. Coxiella burnetii is highly infectious—meaning even a small exposure may cause disease—and is typically transmitted through inhalation of contaminated aerosols from the urine, feces, or birth products of infected animals.

While Q fever can be acute or chronic, its acute form often presents as an undifferentiated febrile illness, making it easy to mistake for influenza or other common infections. However, unrecognized and untreated Q fever, especially chronic forms, can lead to fatal complications, such as endocarditis.

For more on infectious diseases and timely diagnosis, visit our Conditions & Treatments page.

Understanding the Symptoms of Q Fever

The clinical manifestation of Q fever is multifaceted, with symptoms often depending on the phase, immune status of the patient, and extent of exposure.

Early and Acute Q Fever Symptoms

1. Incubation Period

The incubation period—the time from exposure to symptom onset—ranges widely from 2 to 3 weeks, with most symptoms developing around day 18 post-exposure. Individuals may not recall the exact time of infection, further complicating the clinical picture.

2. Sudden Onset of Flu-like Illness

Most acute Q fever cases (up to 60%) present with non-specific, flu-like symptoms. Distinct features, however, aid identification:

a. High Fever

• One of the most consistent and prominent features.
• Rapid onset (≥39°C/102°F), often with chills.
• May occur as a single spike or as relapsing waves.

b. Severe Headache

• Often described as retro-orbital or behind the eyes.
• Throbbing, persistent, and unresponsive to general analgesics.
• May be accompanied by photophobia (sensitivity to light).

c. Myalgia and Arthralgia

• Muscle and joint pains can be pronounced, sometimes mimicking rheumatologic disorders.
• Affects lower back, thighs, and neck predominantly.

d. Fatigue and Malaise

• Profound exhaustion, often out of proportion to fever and other physical findings.
• Patients may struggle with routine activities, requiring prolonged bed rest.

e. Sweats and Chills

• Profuse sweating, often nocturnal, and rigors (intense chills).

3. Respiratory Symptoms

Up to 50% of patients have respiratory manifestations, including:

• Non-productive, dry cough.
• Pleuritic chest pain.
• Mild shortness of breath.

Acute Q fever pneumonia can occur, manifesting with:

• Patchy infiltrates on chest x-ray.
• Minimal crackles or wheezing on auscultation.
• Rarely, frank respiratory distress.

4. Hepatic Involvement (Hepatitis)

• Coxiella burnetii has a predilection for the liver:
• 85% of patients have some evidence of hepatic dysfunction, shown as enzyme elevations.
• Clinical signs: right upper quadrant pain, mild jaundice (rare), dark urine, hepatomegaly.
• Most hepatic symptoms are subclinical except for lab abnormalities.

5. Gastrointestinal Symptoms

• Nausea, vomiting.
• Diarrhea or abdominal pain in 15–30% of cases.

6. Skin Manifestations

• A non-specific, mild maculopapular rash occurs in less than 10% of cases.
• May be seen on the trunk or extremities, fading within days.

7. Cardiovascular and Neurological Symptoms

• Transient hypotension, palpitations, or arrhythmias may occur.
• Meningitic symptoms: Neck stiffness and photophobia (rare, may indicate neurological involvement).

8. Asymptomatic Presentations

Crucially, up to 60% of infected individuals may remain entirely asymptomatic but can still develop chronic disease or complications.

Chronic Q Fever Symptoms

Chronic Q fever develops months to years after the initial infection (6 months - several years), most often in people with risk factors such as valvular heart disease, vascular prostheses, or chronic immunosuppression.

1. Endocarditis

• The most common and feared chronic manifestation.
• Persistent low-grade fever.
• Night sweats.
• Weight loss over weeks to months.
• Heart murmurs on examination, worsening heart failure signs (edema, dyspnea, fatigue).
• May mimic classic infective endocarditis but blood cultures are typically negative (“culture-negative endocarditis”).

2. Chronic Vascular Infections

• Occur in patients with aortic aneurysms or vascular grafts.
• Back, abdominal, or limb pain (depending on location).
• Non-healing wounds, signs of sepsis, or embolic phenomena.

3. Osteoarticular and Other Complications

• Rarely, Q fever may cause chronic bone and joint infections.

4. Fatigue Syndrome

• Persistent, disabling fatigue may follow acute infection (Chronic Q fever fatigue syndrome).
• Profound lethargy, concentration difficulties, insomnia, myalgia.

Atypical and Complicated Presentations

Q fever is known as the “Great Imitator” among infectious diseases because of its diverse organ involvement and the resulting array of symptoms.

1. Neurological Manifestations

• Encephalitis or meningitis: Severe headaches, confusion, neck stiffness, photophobia, possible seizures.
• Guillain-Barré Syndrome-like paralysis (rare).
• Peripheral neuropathy.

2. Cardiac and Vascular Complications

• Pericarditis (inflammation of the heart lining).
• Myocarditis (inflammation of heart muscle).

3. Pregnancy Complications

• Q fever in pregnancy can cause spontaneous abortion, premature delivery, or fetal death.
• Chronic infection risk is also higher in pregnant women.

4. Immune System and Hematologic Effects

• Thrombocytopenia (low platelet count).
• Lymphadenopathy (swollen glands).

5. Kidney and Multi-organ Involvement

• Rarely causes glomerulonephritis or multi-organ dysfunction in severe cases.

Risk Factors Influencing Symptom Severity

Individuals in certain groups may develop more severe or atypical presentations of Q fever:

• Age: Elderly are prone to chronic forms, especially endocarditis.
• Gender: Males are more frequently symptomatic.
• Immunosuppression: Patients with HIV/AIDS, organ transplants, or those on immune-modulating drugs.
• Pregnancy: Higher risk of persistent infection and fetal complications.
• Pre-existing heart or vascular disease: Defective valves or vascular grafts predispose to chronic Q fever.

Long-Term Consequences and Complications

Even after apparent recovery, post-Q fever fatigue syndrome affects 10–25% of patients, manifesting as chronic exhaustion, impaired memory, and muscle pain.

Complications to Watch:

• Chronic Q fever endocarditis (requires specialist management for years)
• Hepatic fibrosis from severe hepatitis
• Renal impairment in multi-organ cases
• Fetal complications in pregnant women
• Persistent immune dysfunction or autoimmunity