Overview
Highly infectious zoonotic disease caused by Coxiella burnetii, transmitted via contaminated aerosols from livestock, presenting as fever, pneumonia, or hepatitis.
Overview
Q fever is a highly infectious zoonotic disease caused by the bacterium Coxiella burnetii. It is transmitted primarily through inhalation of contaminated aerosols from infected livestock (cattle, sheep, goats) and can present as acute febrile illness or develop into chronic infection.
Overview
Q fever is caused by the obligate intracellular bacterium Coxiella burnetii, one of the most infectious organisms known — a single bacterium can cause disease in humans. Transmission occurs primarily by inhaling contaminated aerosols from infected animal birthing products, milk, urine, or feces.\n\nMost acute infections are self-limiting febrile illnesses, but Q fever can also cause atypical pneumonia and hepatitis. A small percentage of cases progress to chronic Q fever, most commonly presenting as endocarditis (heart valve infection). A vaccine (Q-Vax) is available in Australia for occupational risk groups.
Emergency Signs
- persistent high fever unresponsive to standard treatment lasting more than 2 weeks\n- signs of endocarditis: new heart murmur, unexplained prolonged fever, embolic phenomena (stroke-like symptoms, skin lesions)\n- jaundice or liver enlargement suggesting hepatitis\n- severe headache with confusion
Detailed Symptoms
Most common signs and symptoms
Acute Q fever (most common): Sudden onset of high fever (up to 40°C), severe headache, muscle pain, extreme fatigue, and dry cough. Atypical pneumonia occurs in 30–50% of symptomatic cases. Hepatitis (liver inflammation) develops in approximately 40%. Many infections are asymptomatic or mild.\n\nChronic Q fever: Develops in 1–5% of acute cases, primarily as endocarditis. Also manifests as chronic hepatitis, osteomyelitis, or vascular graft infection. May appear months to years after acute infection.
Knowing the symptoms is the first step to a quick response.
Course of Disease
Incubation period is typically 2–3 weeks (range 2–48 days). Acute illness lasts 1–3 weeks and is self-limiting in most cases. Chronic Q fever may develop 1–6 months after acute infection, particularly in individuals with pre-existing heart valve disease, vascular grafts, or immunosuppression.
Diagnosis
How this disease is identified
Serology (immunofluorescence assay) is the reference method — demonstrating seroconversion or a significant rise in antibody titers. Differentiation between acute (Phase II antibodies predominant) and chronic (high Phase I antibody titers) forms is important. PCR on blood during the acute phase can provide early diagnosis. Culture is possible but requires biosafety level 3 facilities.
Treatment
Available treatment methods
Acute Q fever is treated with antibiotics (typically doxycycline) for 14 days, most effective when started within the first 3 days of symptoms. Chronic Q fever (endocarditis) requires prolonged combination antibiotic therapy for at least 18 months with regular monitoring. Treatment decisions should be made by a physician familiar with Q fever management. Most people with acute Q fever recover fully without treatment, but antibiotics shorten illness duration.
Most cases are effectively treated with early diagnosis.
Prevention Details
How to protect yourself
- avoid exposure to livestock birthing products (placenta, amniotic fluid)\n- do not consume unpasteurized dairy products\n- occupational hygiene measures when handling animals\n- Q-Vax vaccine is available in Australia for high-risk workers (requires pre-vaccination screening)\n- proper disposal of animal birthing materials\n- pasteurization of milk and dairy products
Preparation is the best protection.
Travel Advice
- travelers to agricultural areas should be aware of Q fever risk\n- avoid direct contact with livestock, especially during birthing season\n- do not consume unpasteurized milk or dairy products\n- vaccination (Q-Vax) is available in Australia for occupational risk groups — discuss with a travel medicine specialist if relevant\n- seek medical attention for unexplained fever after livestock exposure
How common is it?
Statistics and geographic data
Q fever occurs worldwide wherever livestock are raised. It is endemic in Mediterranean countries, the Middle East, and Australia. Notable outbreaks include the large Netherlands epidemic of 2007–2010 with over 4,000 confirmed cases. Occupational risk is highest for farmers, veterinarians, and abattoir workers. Seasonal peaks coincide with livestock birthing seasons.
Risk Factors
Who is most at risk
- occupational contact with livestock, especially during birthing season\n- living near farms or agricultural areas\n- immunosuppression\n- pre-existing heart valve disease (risk factor for chronic Q fever endocarditis)\n- pregnancy (risk of obstetric complications including miscarriage)\n- consumption of unpasteurized dairy products
Complications Details
Potential complications
Post-Q fever fatigue syndrome affects approximately 20% of acute cases and can persist for months. Chronic endocarditis develops in 1–5% of acute Q fever cases and is the most serious complication. Other complications include hepatic granulomas, pregnancy complications (miscarriage, premature delivery, low birth weight), osteomyelitis, and vascular graft infection. Individuals with pre-existing valve disease are at highest risk for chronic complications.
Recovery & Outlook
Expected outcomes and recovery
Acute Q fever has less than 2% mortality and most patients recover fully within 2–3 weeks. Post-Q fever fatigue syndrome develops in approximately 20% of cases and can persist for months. Chronic Q fever (endocarditis) is serious with up to 25% mortality without treatment, but outcomes are manageable with prolonged antibiotic therapy and monitoring.