What is it?
Q fever is caused by a specific type of bacteria carried by animals, most commonly sheep, goats and cattle. When you inhale barnyard dust particles contaminated by infected animals, you may become infected.
Most people with Q fever have no initial symptoms, but some experience flu-like symptoms or develop pneumonia or hepatitis. This acute form of Q fever can lead to chronic Q fever, which is a serious disease that can last three to four years, can affect your heart, liver, brain and lungs, and is often fatal.
Acute Q fever usually clears up within a few weeks with no treatment. If you have symptoms, your doctor will likely prescribe antibiotics. Chronic Q fever requires specific antibiotic treatment, multiple follow-up tests and possibly surgery.
The signs and symptoms for Q fever vary widely. People with acute Q fever may have no symptoms at all, while chronic Q fever typically affects the heart and other major organs.
Acute Q fever
More than half the people infected with acute Q fever never show symptoms. If you do have symptoms, you'll notice them about two to three weeks after exposure to the bacteria. The infection may mimic the flu, causing these signs and symptoms:
- High fever (104 degrees Fahrenheit, or 40 degrees Celsius)
- Severe headache
- Sore throat
- Cough, which may be dry or productive
- Chest pain
- Abdominal pain
- Purplish rash
- Severe muscle pain
Chronic Q fever
If you have had Q fever for more than six months, it's considered chronic. Chronic Q fever can develop anytime between one and 20 years after you first had acute Q fever, even if you didn't show symptoms initially.
The symptoms of chronic Q fever vary depending on how it manifests itself. Different ways chronic Q fever can affect you include:
- Q fever endocarditis. With endocarditis, the heart's inner lining is inflamed, which can lead to damage of the heart's valves. Signs and symptoms include prolonged fever, night sweats, chills, fatigue and shortness of breath.
- Blood vessel infections. When the bacteria that cause Q fever infect your blood vessels, you may have a fever, fatigue, loss of appetite and weight loss.
- Other types of chronic Q fever. Rarely, chronic Q fever can manifest itself as a bone infection (osteomyelitis), chronic lung infection or chronic fatigue, each with its own set of symptoms.
Coxiella burnetii bacteria typically infect animals. The infection most commonly affects sheep, goats and cattle, but can also affect pets, such as cats, dogs, birds and rabbits. These mammals transmit the bacteria through their urine, feces, milk and birth products, such as placenta and amniotic fluid. When these substances dry, the bacteria in them become part of the barnyard dust that floats in the air. The infection is transmitted to humans through the lungs, when you inhale contaminated barnyard dust.
Rarely, you can get Q fever from drinking large amounts of unpasteurized milk or by being bitten by an infected wood tick.
Certain factors can increase your risk of getting acute Q fever, including:
- Occupation. Certain occupations place you at higher risk because you're exposed to animals and animal products as part of your job. At-risk occupations include veterinary medicine, meat processing, livestock farming and animal research.
- Location. Simply being near a farm or farming facility may put you at higher risk of Q fever, because the bacteria can travel long distances accompanying dust particles in the air.
- Your sex. Men are more likely to develop symptomatic acute Q fever.
- History of acute Q fever. Anyone who has had Q fever is at risk of developing the chronic form of the disease. This risk is greater if you also have heart valve disease, blood vessel abnormalities, chronic kidney disease or a weakened immune system.
Q fever can affect your heart, liver, lungs and brain, giving rise to serious complications, such as:
- Endocarditis, an inflammation of the membrane surrounding your heart
- Meningitis, an inflammation of the membrane surrounding your brain and spinal cord
- Acute respiratory distress, a medical emergency in which you're not getting enough oxygen
- Pregnancy complications, including miscarriage, low birth weight, premature birth, intrauterine growth retardation and stillbirth
To diagnose Q fever, your doctor will perform one or more blood tests, along with additional tests if chronic Q fever is suspected.
- Platelet count. Performing a platelet count may suggest Q fever, but it can't provide a definite diagnosis.
- Serologic testing. To make a specific diagnosis of Q fever, your doctor will test your blood serum for antibodies to the Coxiella burnetii antigen.
- Echocardiography. If chronic Q fever is suspected, your doctor may do an echocardiogram to check for lesions on your heart valves, the most common sign of endocarditis. If no lesions are found on the echocardiogram, your doctor may want you to return in three or six months for more serologic tests and another echocardiogram.