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Q Fever

Q Fever

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What is Q Fever?

Q fever is a disease (acute or sometimes chronic) caused by the bacteria Coxiella burnetii. This disease is found worldwide. The bacteria naturally infects mammals; primarily goats, sheep and cattle but, has also been found in birds, and ticks. Thirty-five species of ticks have been identified as natural hosts of this bacteria.

The most common route of transmission to humans is through inhalation of dust that has been contaminated by infected animal feces, urine, milk, and birth products. The organism is extremely hardy and resistant to heat, drying, and many common disinfectants, which enable the bacteria to survive for long periods in the environment. High-risk occupations include farming, ranching, veterinary care and animal research.

Other less common modes of transmission, include tick bites, ingestion of unpasteurized milk or dairy products, and human to human transmission.

Acute infection with this bacteria is highly variable. Q fever is usually a mild disease with flu-like symptoms. Many people exposed to this disease have no symptoms at all. However, in a small percentage of people, the infection can resurface years later. This more deadly, chronic form, of Q fever can damage heart, liver, brain and lungs. C. burnetii is highly infectious. Humans that are susceptible to this disease can be infected by a single organism. It is considered a significant threat for bio warfare and is classified as a Category B agent of bioterrorism.

Mild cases of Q fever clear up quickly with antibiotic treatment. But if Q fever recurs, you may need to take antibiotics for at least 18 months.

Is Q Fever in Colorado?

Yes, Q-fever is in Colorado. Seven cases of acute Q-fever were reported within Colorado in 2015, with a 5.4 case average for 2011 through 2015. There were zero cases of chronic Q-fever in 2015, with a case average of 1.6 for the years 2011-2015. Though this disease is most commonly associated with inhalation of dust contaminated with infected animal feces, urine, milk, or birth products; tick vectors of this disease are also known to occur in Colorado and include the Brown Dog Tick (Rhipicephalus sanguineus), Rocky Mountain Wood Tick (Dermacentor andersoni).

What are Q Fever Symptoms?

Q fever can cause acute or chronic illness. Acute symptoms usually develop within 2-3 weeks of exposure, although 50% of infected persons may be asymptomatic.

The severity and combination of signs and symptoms vary greatly. About half the people infected with Q fever will get sick. Signs and symptoms of Q fever may include:

  • High fever (up to 105°F)
  • Fatigue
  • Severe headache
  • General malaise
  • Myalgia
  • Chills or sweats
  • Non-productive cough
  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Chest pain

Most people with acute Q fever infection recover completely. People who develop severe cases may develop inflammation of the lungs (pneumonia) or liver (hepatitis), myocarditis, or central nervous system complications.

Pregnant women- Women who are infected during pregnancy may be at risk for miscarriage, stillbirth, pre-term delivery or low infant birth weight. Women infected by C. burnetii during pregnancy and those with immunosuppression have also been linked to development of chronic Q fever.

Chronic Q fever- A very small percentage of people who become infected with Q fever develop a more serious infection called chronic Q fever. Chronic Q fever is serious and can be fatal if not treated correctly. It may present within weeks or many years following an acute infection. Anyone who has been infected with C. burnetii is at risk for developing chronic Q fever, however those with a history of heart valve disease, blood vessel abnormalities, or who are immunosuppressed are at higher risk. Endocarditis is the most commonly recognized manifestation of chronic Q fever and is fatal if untreated. Patients with endocarditis require early diagnosis and long-term antibiotic treatment (18 months to several years) for a successful outcome. Other forms of chronic Q fever include vascular aneurysms, and infections of bone, liver or reproductive organs.

How is Q Fever Diagnosed?

The symptoms of Q Fever vary from patient to patient and can be difficult to distinguish from other diseases. Diagnosis is based on a combination of clinical presentation, patient history (especially history of contact with animals or animal feces) and serologic tests. Chest radiographs can be useful in patients with respiratory symptoms; where an atypical pneumonia pattern is the most common finding. After a suspect diagnosis is made based on clinical suspicion and treatment has begun, specialized laboratory testing should be used to confirm the diagnosis of Q fever.

Routine blood tests, such as a complete blood cell count (CBC) or a chemistry panel (CMP) may be helpful. Prolonged fever with low platelet count, normal leukocyte count, and elevated liver enzymes are suggestive of acute Q fever infection, but may not be present in all patients.

Chronic Q fever is a risk for anyone with a history of acute Q fever, but are more frequent in persons with valvular disease, blood vessel abnormalities, immunosuppressed persons, and women who were pregnant when they became infected. People a history of Q-fever infection with these risk factors should be routinely monitored using serologic methods for the two years following diagnosis of acute Q fever to ensure rapid diagnosis and treatment of chronic Q fever.

How to test for Q-Fever?

In the early stages of illness, it is recommended to use serologic tests in combination with PCR of whole blood or serum. Laboratory testing and reporting of results can take several weeks, therefore treatment should be initiated as soon as Q fever is suspected and should never be withheld pending the receipt of diagnostic test results.

Diagnostic tests based on the detection of antibodies will frequently appear negative in the first 7-15 days of Patients should be treated based on clinical suspicion alone and not wait for the return of confirmatory tests.

The most frequently used and dependable serologic method for Q fever diagnosis is indirect immunofluorescent antibody (IFA) testing. Culturing of C. burnetii is also possible, but is rarely performed, as laboratory-transmitted cases of Q fever have been reported.

How is Q-Fever treated?

  • Acute Q fever: Most people with acute Q fever will recover without antibiotic treatment. Treatment is generally not recommended for patients who are asymptomatic or who have already recovered from their illness, but might be considered for those at high risk of developing chronic Q fever. For those that require treatment, doxycycline is the recommended first-line treatment for non-pregnant adults with Q fever and is most effective at preventing severe complications if it is started within the first 3 days of symptoms. Quinolone antibiotics are also active against C. burnetii, and are sometime used as an alternative. If signs and symptoms persist or if the patient relapses, treatment should be extended or reinitiated.

Treatment must be based on clinical suspicion and should always begin before laboratory results return. If the patient is treated within the first 3 days of the disease, fever generally subsides within 72 hours. Severely ill patients may require longer periods before their fever resolves.

  • Chronic Q fever: Chronic Q fever is significantly more difficult to treat. It is a serious infection and requires several months of treatment with a combination of antibiotics including doxycycline and hydroxychloroquine. In patients with endocarditis, open ended treatment with doxycycline in combination with either a quinolone or hydroxychloroquine (Plaquenil) is frequently used. Duration of treatment for chronic Q fever is based on serologic response and evidence of clinical improvement (18 months to at least 4 years in some cases). Patients with life-threatening allergies to doxycycline may consider alternate antibiotics such as moxifloxacin, clarithromycin, trimethoprim/sulfamethoxazole and rifampin. Serologic monitoring of a patient with chronic Q fever should be done in consultation with an infectious disease specialist.


Colorado Department of Health and Environment webpage and personal communication with former CDPHE Epidemiologist, Dr. Leah Colton

Columbia University- Lyme and Tick-borne Diseases Research Center

Centers for Disease Control and Prevention