Other Names: Q fever pneumonia; Coxiella Burnetii fever; Query fever
Q fever is a worldwide disease with acute and chronic stages caused by the bacteria known as Coxiella burnetii. This bacteria naturally infects some animals, such as goats, sheep, and cattle. C. burnetii bacteria are found in the birth products (i.e. placenta, amniotic fluid), urine, feces, and milk of infected animals.
People get infected by breathing in dust that has been contaminated by infected animal feces, urine, milk, and birth products that contain Coxiella burnetii. Direct contact (e.g. touching, being licked) with an animal is not required to become sick with Q fever. People may also get sick with Q fever by eating contaminated, unpasteurized dairy products. Rarely, Q fever has been spread through blood transfusion, from a pregnant woman to her fetus, or through sex.
Certain professions are at increased risk for exposure to C. burnetii, including veterinarians, meat processing plant workers, dairy workers, livestock farmers, and researchers at facilities housing sheep and goats. People working in these areas may need to take extra precautions
Signs and Symptoms
About 5 out of 10 people infected with Coxiella burnetii will get sick. Illness typically develops 2-3 weeks after being exposed to the bacteria. Signs and symptoms of Q fever may include:
- Chills or sweats
- Fatigue (tiredness)
- Muscle aches
- Nausea, vomiting, or diarrhea
- Chest pain
- Stomach pain
- Weight loss
- Non-productive cough
Symptoms can be mild or severe. People who develop severe disease may experience infection of the lungs (pneumonia) or liver (hepatitis). Women who are infected during pregnancy may be at risk for miscarriage, stillbirth, pre-term delivery, or low infant birth weight.
Chronic Q fever A very small percentage of people (less than 5 out of 100) who become infected with C. burnetii bacteria develop a more serious infection called chronic Q fever. Chronic Q fever develops months or years following initial Q fever infection. People with chronic Q fever often develop an infection of one or more heart valves (called endocarditis). People with endocarditis may experience night sweats, fatigue, shortness of breath, weight loss, or swelling of their limbs. A healthcare provider will need to perform a series of tests to diagnose endocarditis.
Diagnosis is usually based on serology(looking for an antibody response) rather than looking for the organism itself. Serology allows the detection of chronic infection by the appearance of high levels of the antibody against the virulent form of the bacterium. Molecular detection of bacterial DNA is increasingly used. Culture is technically difficult and not routinely available in most microbiology laboratories.
Q fever can cause endocarditis (infection of the heart valves) which may require transoesophageal echocardiography to diagnose. Q fever hepatitis manifests as an elevation of alanine transaminase and aspartate transaminase, but a definitive diagnosis is only possible on liver biopsy, which shows the characteristic fibrin ring granulomas.
Most people who are sick with Q fever will recover without antibiotic treatment. However, for people who develop Q fever disease, treatment with 2 weeks of doxycycline antibiotic is recommended. Chronic Q fever A life-threatening infection, requiring several months of antibiotic treatment. Treated with a combination of antibiotics including doxycycline and hydroxychloroquine for several months.
- Protection is offered by Q-Vax, a whole-cell, inactivated vaccine developed by an Australian vaccine manufacturing company, CSL Limited. The intradermal vaccination is composed of killed C. burnetii organisms. Skin and blood tests should be done before vaccination to identify pre-existing immunity, because vaccinating people who already have an immunity can result in a severe local reaction. After a single dose of vaccine, protective immunity lasts for many years. Revaccination is not generally required. Annual screening is typically recommended.
- Q fever vaccines are not available in the United States.
- Reduce your risk of getting Q fever by avoiding contact with animals, especially while animals are giving birth. Animals can be infected with Coxiella burnetii and appear healthy.
- Do not consume raw milk or raw milk products.
- If you have been diagnosed with Q fever and have a history of heart valve disease, blood vessel abnormalities, a weakened immune system, or are pregnant, talk to your healthcare provider about your risk for developing chronic Q fever.
Q fever was first recognized as a human disease in Australia in 1935 and in the United States in the early 1940s. The “Q” stands for “query” and was applied at a time when the cause was unknown. C. burnetii can survive for long periods of time in the environment and may be carried long distances by wind.
Q fever was made a nationally notifiable disease in the United States in 1999. The number of Q fever cases reported to CDC increased, from 19 cases reported in 2000, to 173 cases reported in 2007. In 2008, the Q fever case definition was changed to allow for the reporting of chronic and acute Q fever separately. During 2008–2013 the number of reported cases decreased slightly, relative to 2007, returning to high levels in 2014. In 2017, 153 acute Q fever cases were reported, as well as 40 chronic Q fever cases.