Many people infected with Q fever never show symptoms. If you do have symptoms, you'll probably notice them between three and 30 days after exposure to the bacteria. Signs and symptoms may include:

• High fever, up to 105 F (41 C)
• Severe headache
• Fatigue
• Chills
• Cough
• Nausea
• Vomiting
• Diarrhea
• Sensitivity to light

Q fever is caused by the bacterium Coxiella burnetii, commonly found in sheep, goats and cattle. The bacterium can also infect pets, including cats, dogs and rabbits.

These animals transmit the bacteria through their urine, feces, milk and birthing products — such as the 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 usually transmitted to humans through their lungs, when they inhale contaminated barnyard dust.

Certain factors can increase your risk of being infected with Q fever bacteria, 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.
• Time of year. Q fever can occur at any time of the year, but the number of infections usually peaks in April and May in the U.S.

Risk factors for chronic Q fever

The risk of eventually developing the more deadly form of Q fever is increased in people who have:

• Heart valve disease
• Blood vessel abnormalities
• Weakened immune systems
• Impaired kidney function

A Q fever recurrence can affect your heart, liver, lungs and brain, giving rise to serious complications, such as:

• Endocarditis. An inflammation of the membrane inside your heart, endocarditis can severely damage your heart valves. Endocarditis is the most deadly of Q fever's complications.
• Lung issues. Some people who have Q fever develop pneumonia. This can lead to acute respiratory distress, a medical emergency in which you're not getting enough oxygen.
• Pregnancy problems. Chronic Q fever increases the risk of miscarriage, low birth weight, premature birth and stillbirth.
• Liver damage. Some people who have Q fever develop hepatitis, an inflammation of the liver that interferes with its function.
• Meningitis. Q fever can cause meningitis, an inflammation of the membrane surrounding your brain and spinal cord.