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
• Fatigue
• Sore throat
• Chills
• Sweats
• Cough, which may be dry or productive
• Chest pain
• Abdominal pain
• Nausea
• Vomiting
• Diarrhea
• 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
• Pneumonia
• 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

What you can do
If you've been exposed to any barnyard or livestock environments within the last three weeks and develop flu-like symptoms, talk to your doctor. Similarly, if you develop flu-like symptoms a few weeks after handling any animal birthing products, such as placenta, amniotic fluid or the coats of newborn animals, make an appointment to see your doctor. While Q fever is uncommon, it's still best to identify the cause of your symptoms.

What to expect
The flu-like symptoms associated with this infection aren't unique to Q fever. In an effort to narrow the possibilities, your doctor may ask if your medical history contains any links to endocarditis, pneumonia or hepatitis — all problems associated with Q fever. Also, because environmental factors play a large role in acquiring this infection, your doctor may ask about your recent exposure to areas that may have placed you at risk of acquiring Q fever infection. A blood test then can confirm the diagnosis.

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.

Treatment for Q fever depends on whether the infection is acute or chronic and whether you're pregnant.

Acute Q fever treatment
Mild or nonsymptomatic cases of acute Q fever often get better in about two weeks with no treatment. However, even if you have no symptoms your doctor may want to provide treatment in order to prevent future complications.

The standard treatment for acute Q fever is doxycycline, an antibiotic. The severity of your infection will determine the length of time you need to take the antibiotic, but the usual medication course is two to three weeks. It's important to get treatment as soon as you notice symptoms, because the antibiotics are the most effective when they're initiated within one week of symptoms' onset.

Sometimes, acute Q fever can come back. Your doctor may ask you to return in six months for serologic testing. If Q fever bacteria antibodies are found again, you'll likely need another round of antibiotics.

Chronic Q fever treatment
Chronic Q fever is treated with a combination of antibiotics taken for at least 18 months. In more-advanced cases, you may need to take the antibiotics for as long as four years.

If you have Q fever endocarditis, you may need surgery to remove or graft damaged heart valves or repair an aneurysm. Although treatments are available, complications can quickly multiply, and they may prove fatal. Even after successful chronic Q fever treatment, you'll need to go back for follow-up tests for years in case the infection returns.

Treatment of Q fever during pregnancy
Treating Q fever during pregnancy can be a challenge, because the usual antibiotics prescribed for Q fever are not recommended during pregnancy. Some women elect to wait until after delivery to treat Q fever, but that decision has risks as well. Pregnancy is a risk factor for developing chronic Q fever, and acute Q fever can cause multiple complications for the baby as well. If you're pregnant and have Q fever, be sure you understand all of your treatment options and their risks.

If you're at specific risk of Q fever, following these recommendations may prevent infection:

• Carefully dispose of animal products. The byproducts of an animal birth (including placenta and fetal membranes) can carry the Q fever bacteria. Properly dispose of all animal waste material to reduce risk.
• Use disinfectants. Use specific cleaners and disinfectants labeled effective against C. burnetii bacteria.
• Wash your hands. Thorough hand washing throughout the day may prevent the spread of C. burnetii and other bacteria.
• Drink only pasteurized milk. Drinking large amounts of unprocessed dairy products may expose you to harmful bacteria.
• Get vaccinated if possible. A tested and highly effective vaccine is available in Australia, though the vaccine is not commercially available in the United States.
• Perform laboratory procedures appropriately. If you're a researcher working with animals, take appropriate precautions and follow guidelines to reduce your risk.
• Quarantine imported animals. Since animal infection rates vary by country, keep imported animals away from the rest of the herd until you can verify that the animal is free of infection.
• Regularly test animals. If you work in an animal environment, regularly test the animals you work with for antibodies to the Coxiella burnetii bacteria, and treat as appropriate.
• Avoid farms and animal environments if you're at risk. If you are pregnant, are immunocompromised or have valve disease, do all you can to avoid barnyard and livestock dust that may be contaminated.