Illness typically develops 2-3 weeks after being exposed to the bacterium. Signs and symptoms of Q fever may include fever, chills or sweats, fatigue, headache, muscle aches, nausea, vomiting, diarrhea, chest pain, stomach pain, weight loss and a non-productive cough. Symptoms can be mild or severe. People who develop severe disease may experience infection of the lungs (pneumonia) or liver (hepatitis).
Less than 5% of people who become infected with Coxiella burnetii develop a more serious infection called chronic Q fever. This can occur months or years after the initial infection and often leads to inflammation of the heart valves (endocarditis). Chronic Q fever is more likely to occur in people with preexisting heart valve disease or blood vessel abnormalities or in people with weakened immune systems.