Q fever

Disease Overview

Summary

Q fever is an infectious disease that is spread by the inhalation or ingestion of a bacterium known as Coxiella burnetii, which belongs to the order of Legionellales. Animals such as cattle, sheep and goats are common bacterial hosts for this bacterium. C. burnetii is spread mainly by breathing contaminated air or eating or drinking contaminated food. Farm workers, especially those who work with animals, people who work in slaughterhouses and veterinarians are especially vulnerable to this disease. Other forms of transmission are rare but include tick bites and human to human transmission. Q fever causes highly variable symptoms ranging from acute (often self-limited) infection to fatal chronic infection. Progression of Q fever from acute infection to chronic fever occurs in less than 5% of patients. Infections that do not cause outward symptoms (subclinical) or no symptoms (asymptomatic) are also common. Acute Q fever is treated with antibiotics. Treatment for chronic Q fever is more complex and depends on an individual’s presenting symptoms. People of all ages are susceptible to Q fever.

Introduction

Since infection can occur because of airborne transmission and the bacterium is very resistant to environmental conditions such heat and pressure, C. burnetti was included on the list of possible bacteriological weapons.

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Synonyms

• Q fever pneumonia, atypical pneumonia
• Coxiella burnetii fever
• query fever
• Coxiellosis
• nine-mile fever
• quadrilateral fever

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Subdivisions

• acute Q fever
• chronic Q fever

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Signs & Symptoms

The symptoms of Q fever can vary dramatically from one person to another. Infection can result in no apparent symptoms (asymptomatic); an acute form of disease characterized by a flu-like illness that either goes away on its own (self-limited) or causes more serious symptoms; or a chronic form that can be associated with serious complications. Researchers believe that a variety of factors may influence the severity of Q fever including age, gender and a person’s general health, including pre-existing medical conditions (e.g., heart disease).

Acute Q Fever

The acute form of Q fever starts approximately two to three weeks after exposure to the bacterium. Acute Q fever is characterized by flu-like symptoms such as high fevers, chills, muscle pain (myalgia), muscle weakness, fatigue and headaches. In some patients, fevers do not occur. Additional nonspecific symptoms can potentially occur including cough, chest pain, sore throat, skin rash or gastrointestinal symptoms. Many people also suffer from small areas of inflammation (granuloma).

Pneumonia and inflammation of the liver (hepatitis) are commonly associated with acute Q fever. Pneumonia is often mild but can potentially progress to cause acute respiratory distress syndrome (ARDS). Hepatitis may cause abnormal enlargement of the liver (hepatomegaly). More rarely, it can cause yellowing of the skin and the whites of the eyes (jaundice). Other symptoms can occur in some affected individuals including inflammation of the muscular wall of the heart (myocarditis), inflammation of the sac-like membrane that surrounds the heart (pericarditis) and the development of a purple skin rash caused by bleeding (hemorrhaging) from tiny blood vessels just below the surface of the skin.

Acute Q fever may present as a neurological disease caused by inflammation of the thin membrane covering the brain and spinal cord or the brain (meningoencephalitis). In some individuals, acute Q fever can affect the kidneys, thyroids or genitals.

Chronic Q Fever

Chronic Q fever may occur months to years after acute disease or may occur without a previous history of symptomatic acute Q fever. Most cases of chronic Q fever occur in individuals with predisposing conditions such as existing heart valve or blood vessel (vascular) abnormalities or a compromised immune system.

The most common manifestation of chronic Q fever is inflammation of the thin membrane lining the inside of the heart and heart valves (infective endocarditis), potentially damaging the heart valves or heart tissue. Inflammation of heart muscle (myocarditis) is rarely seen but also possible. Other symptoms include inflammation of blood vessels (vasculitis), low red blood cell count (hemoglobin), low platelet count (thrombocytopenia), anticardiolipin IgG antibody positivity, antimitochondrial antibody positivity and blood in urine (hematuria). Affected individuals can develop congestive heart failure, a serious complication in which a limited ability to circulate blood to the lungs and the rest of the body results in fluid buildup in the heart, lungs and various body tissues. In addition, Q fever can cause liver inflammation (hepatitis), enlarged liver (hepatomegaly), enlarged liver and spleen (hepatosplenomegaly), fluid around lungs (pleural effusions) and respiratory distress.

Less commonly, chronic Q fever can present as an infection of the bones and joints (osteoarticular infection) such as osteomyelitis or osteoarthritis, which can cause bone and joint pain. Vascular infections, chronic hepatitis and chronic pulmonary disease are also seen in some patients. Chronic hepatitis can cause enlargement of the liver or jaundice. Chronic pulmonary disease can cause difficulty breathing (dyspnea) and other respiratory abnormalities. Other less common symptoms include abnormal heart valve morphology, immunodeficiency, increased circulating antibody level, flat and raised skin lesions (maculopapular exanthema), pneumonia, red or purple spots on the skin (purpura) and rheumatoid factor positivity.

Individuals with chronic Q fever may also experience a variety of symptoms similar to those experienced by acute Q Fever patients, including prolonged fevers (although fevers are often absent), joint pain (arthralgia), muscle pain (myalgia), night sweats, chills, fatigue and unintended weight loss.
Some individuals with Q fever develop long-term complications such as chronic, persistent fatigue. Some researchers believe that infection with Q fever increases an individual’s risk of developing cardiovascular disease later in life.

The rarest symptoms (approximately 1%- 4% of individuals) include abnormal function of the left ventricle, abnormal amyloid build-up (amyloidosis), inflammation of the gallbladder (cholecystitis), inflammation of the brain (encephalitis), lupus anticoagulant, swollen lymph nodes (lymphadenopathy) or inflammation of fluid and membrane around the brain and spinal cord (meningitis).

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Causes

Q fever is caused by inhalation or ingestion of the bacterium Coxiella burnetii. People are most often exposed to the bacterium from the milk, urine and feces of infected animals (for example, by inhaling contaminated air in a barnyard). When these waste substances dry in the air, the bacteria are able to mix with the barnyard dust that floats around. Consequently, this infection is primarily transferred to humans through their lungs when they breathe the contaminated dust. Also, when an infected animal gives birth, the bacteria may be present in high numbers in the amniotic fluid and placenta. Q fever bacterium primarily infects farm animals such as cattle sheep and goats. However, it has been reported in a wide variety of animals including domesticated animals such as dogs, cats and rabbits. The C. burnetii bacterium is highly infectious. The bacterium can survive in the environment for lengthy periods of time because it is resistant to environmental conditions such heat and pressure. It is also resistant to many common disinfectants.

Less common modes of transmission to humans include working in a slaughterhouse, drinking unpasteurized milk and hunting, slaughtering or dressing infected animals. According to the medical literature, in extremely rare cases, human-to-human transmission has been reported.
The mode of transmission in wild and domestic animals is different from the mode of transmission in humans. Animals become infected with C. burnetii from infected ticks. Originally, Q fever was classified as a rickettsial disease, a group of infectious diseases most often spread to humans from ticks. However, based on DNA-DNA hybridization studies and genome sequencing, C. burnetii was placed to the order of Legionellales, which also contains Legionella pneumophila, the bacterium that causes Legionnaires disease.

People with pre-existing conditions are at higher risk of developing chronic Q fever. These conditions include heart valve disease, blood vessel abnormalities, weakened immune system or an impaired kidney function.

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Affected populations

Q fever occurs worldwide and can affect individuals of every racial and ethnic background. The incidence of Q fever is unknown because in many countries it is not a reportable disease. Researchers believe that the infection is underreported. From 2000-2012, the incidence rate for this disease in the United States was 0.38 cases per million people per year. There have been higher incidence rates in certain countries such as the Netherlands, where there were reports of thousands of human cases.

Q fever has occurred more often in men than women, however, this trend is attributed to the fact that more men work in occupations where exposure to C. burnetii bacterium is likely to occur. Q fever can affect individuals of any age, but affected children are rarely reported. Some researchers have speculated that children develop symptoms that are milder and occur less often compared to adults.

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Disorders with Similar Symptoms

Symptoms of the following disorders can be similar to those of Q fever. Comparisons may be useful for a differential diagnosis.

Q fever must be differentiated from other, more common causes of fever, chronic fatigue, weakness, other nonspecific flu-like symptoms and endocarditis. Q fever must also be differentiated from other atypical pneumonias. Atypical pneumonias are a group of diseases in which pneumonia is caused by infection with certain bacteria. This group includes chlamydiosis, bartonellosis, the rickettsial diseases, legionellosis, brucellosis, tularemia and other diseases, including some viral infections.

The rickettsial diseases are a group of infectious disorders caused by exposure to bacteria belonging to the Rickettsiaceae family. The most common rickettsial disease is Rocky Mountain spotted fever (RMSF), caused by the bacterium Rickettsia rickettsii (R. rickettsii). In most cases, the bacteria responsible are thought to be carried and transmitted by certain ticks. The severity of the rickettsial diseases varies greatly. Some affected individuals develop mild symptoms, while others may potentially lead to life-threatening complications. Associated symptoms may include headache, fever, chills, muscle aches (myalgia), joint pain (arthralgia), extreme exhaustion (prostration) and/or a characteristic skin rash. In some people, additional symptoms may include nausea, vomiting, abdominal pain and/or other abnormalities. In some severe forms of the disease, damage to endothelial cells lining blood vessels may result in tissue injury of the heart, lungs, central nervous system, kidneys, liver and/or other organs, leading to potentially life-threatening complications. (For more information on this disorder, choose “Rocky Mountain Spotted Fever” as your search term in the Rare Disease Database).

Legionellosis is due to infection with Legionella species and clinically is seen most commonly as a severe community-acquired pneumonia called Legionnaire’s disease or a less severe form of pulmonary illness called Pontiac fever. Legionnaires’ disease is a rare infectious disease that is caused by the bacterium Legionella pneumophila. The first known outbreak occurred at a hotel that was hosting a meeting of the American Legion organization in Pennsylvania in 1976. In that outbreak, it was found that water in the hotel’s air conditioning system was contaminated with the bacteria. Legionnaires’ disease is most often contracted by inhaling contaminated water from sources such as showers and whirlpool baths. Legionnaires’ disease causes severe pneumonia, chills, fevers, cough and a sharp pain in the side of the chest. There is no evidence of human-to-human transmission. (For more information on this disorder, choose “Legionnaires’” as your search term in the Rare Disease Database).

Brucellosis is an infectious disease that affects livestock and may be transmitted to humans. It is rare in the United States (100 to 200 cases occur each year) but occurs more frequently in other parts of the world. The disorder is caused by bacteria belonging to the genus Brucella. Initial symptoms of infection may be nonspecific including fevers, muscle pain, headache, loss of appetite, profuse sweating and physical weakness. In some people, the symptoms occur suddenly (acute), whereas, in others, symptoms may develop over the course of a few months. If brucellosis is not treated, the disease may take months to resolve once appropriate therapy is begun. Brucellosis may be confined to a certain area of the body (local) or have serious widespread complications that affect various organ systems of the body, including the central nervous system. Brucellosis may be prevented by pasteurizing cow and goat’s milk before drinking. However, farmers and people exposed to butchered meat may also be affected by brucellosis. (For more information on this disorder, choose “brucellosis” as your search term in the Rare Disease Database).

Tularemia is found worldwide but this infectious disease is rare in the U.S. (approximately 120 cases are reported annually). It most often affects small mammals such as rabbits, rodents and hares. It is highly infectious and is most often transmitted to humans by handling an infected animal or being bit by an infected tick or fly. People have not been known to transmit the infection to others. The disease is caused by the bacterium Francisella tularensis. The severity of tularemia varies from mild and self-limiting, to serious and life threatening (about 2%). (For more information on this disorder, choose “tularemia” as your search term in the Rare Disease Database).

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Diagnosis

The signs and symptoms of Q fever are nonspecific and can be associated with a wide variety of diseases. A diagnosis of Q fever usually requires serological examination, which measures and characterizes antibodies. Q fever has two antibody-producing (antigenic) phases called phase I and phase II. These phases can help confirm a diagnosis and can help distinguish acute Q fever infection from chronic Q fever infection. Infected individuals develop specific antibodies against Q fever including immunoglobulin G (IgG), immunoglobulin A (IgA) and immunoglobulin M (IgM). Measuring the levels of these classes of antibodies can help confirm a diagnosis of Q fever. During the acute phase of Q fever, IgG and IgM antibodies may be detected. In chronic Q fever, IgG or IgA levels may be detected.

In acute Q fever, the levels of antibodies to phase II antigen of C. burnetii are higher than those to the phase I antigen. Phase II antigens of C. burnetii are normally detected during the second week of the illness. In chronic Q fever, a high level of phase I antibodies with a constant or falling level of phase II antibodies are common along with other elevated inflammatory markers.

The three most common serological tests for Q fever are indirect immunofluorescence, complement fixation and enzyme-linked immunosorbent assay (ELISA). Indirect immunofluorescence is a test that can detect the presence of specific antibodies in the blood or other fluids. The antibodies are tagged with a substance that causes them to glow when exposed to ultraviolet light. Complement fixation and ELISA tests can also detect the presence of specific antibodies or antigens. Isolation of the infectious agent in cell cultures, embryonated hen’s eggs and laboratory animals is also possible, but requires a special laboratory with biosafety level three (BSL3).

A common test that has been used to aid in the diagnosis of Q fever in some cases is a polymerase chain reaction (PCR) test. A PCR test is a highly sensitive test that amplifies a specific segment or sample of DNA, creating billions of copies of that segment There are three key steps to create the multitude of copies of a segment. First, the DNA strands are heated so they separate. Next, the reaction is cooled so the primer can bind to the DNA. A primer is a short sequence of nucleotides used to provide a starting point for the DNA synthesis reaction. Finally, the temperature of the reaction is raised again to extend the primers and synthesize new DNA strands. This amplified segment can then be studied to detect the presence of C. burnetii infection. It has been employed successfully to detect C. burnetii DNA in cell cultures and biological samples. Although a PCR test is highly sensitive, a negative result does not necessarily rule out a Q fever infection. Reasons for a negative result include inhibition of the PCR or low levels of C. burnetti that are not detectable by the polymerase chain reaction.

Clinical Testing and Work-Up

A physician may order some imaging tests to check the health of the internal organs. A chest X-ray may be used to evaluate for pneumonia, which affects some individuals with Q fever. Additionally, an echocardiography is used if chronic Q fever is suspected. This test can reveal any issues with heart valves.

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Standard Therapies

Antibiotic therapy is used to treat individuals with Q fever. Some mild cases of Q fever may improve without treatment, although antibiotic therapy can usually help reduce the duration of the infection. Physicians recommend that all individuals in whom Q fever is detected receive antibiotic therapy, even those with no recognizable symptoms.

Doxycycline is currently the most used antibiotic therapy for the treatment of individuals with Q fever and is most effective when started within three days of infection. Anti-inflammatory drugs may be used if individuals do not respond to antibiotics. Hydroxychloroquine, which is often used to treat malaria, has also been used to treat Q fever. Hydroxychloroquine can help raise the pH of lysosomal compartments, allowing more effective antibiotic activity toward the bacteria.

Chronic Q fever is more difficult to treat. Endocarditis may require prolonged antibiotic treatment which usually involves treatment with multiple drugs. One such combination is the use of doxycycline and hydroxychloroquine. For patients allergic to doxycycline, trimethoprim-sulfamethoxazole may be used instead. The optimal duration of therapy is unknown and varies from person to person. In individuals with damage to the heart valves or a history of heart failure, surgery may be necessary.

There is currently no vaccine approved by the U.S. Food and Drug Administration (FDA) for Q fever.

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Clinical Trials and Studies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]

Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/

For information about clinical trials sponsored by private sources, contact:
www.centerwatch.com

For information about clinical trials conducted in Europe, contact:
https://www.clinicaltrialsregister.eu/

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References

TEXTBOOKS

Kovacova E, Kazar J. Q Fever. In: NORD Guide to Rare Disorders. Lippincott Williams &Wilkins. Philadelphia, PA. 2003:293.

JOURNAL ARTICLES

Dahlgren FS, McQuiston JH, Massung RF, Anderson AD. Q fever in the United States: summary of case reports from two national surveillance systems, 2000-2012. Am J Trop Med Hyg. 2015;92(2):247-255. doi:10.4269/ajtmh.14-0503

Kersh GJ. Antimicrobial therapies for Q fever. Expert Rev Anti Infect Ther. 2013;11(11):1207-1214. doi:10.1586/14787210.2013.840534

Roest HJI, Tilburg JJHC, Van der Hoek W, Vellema P, et al. The Q fever epidemic in The Netherlands: history, onset, response and reflection. Epidemiol. Infect. 2011; 139: 1-12.

Kersh GJ, Wolfe TM, Fitzpatrick KA, et al. Presence of Coxiella burnetii DNA in the environment of the United States (2006-2008). Appl. Environ. Microbiol.2010;76 (13): 4469-4475.

Omsland A, Cockrell DC, Howe D, et al. Host cell-free growth of the Q fever bacterium Coxiella burnetii. PNAS. 2009;106(11): 4430-4434.

Hartzell JD, Wood-Morris RN, Martinez LJ, Trotta RF. Q fever: epidemiology, diagnosis and treatment. Mayo Clin Proct. 2008; 83:574-79.

Parker NR, Barralet JH, Bell AM. Q fever.Lancet. 2006; 367:679-88.

Karakousis PC, Trucksis M, Dumler JS. Chronic Q fever in the United States.J Clin Microbiol. 2006;44:2283-87.

Marrie TJ. Empiric treatment of ambulatory community-acquired pneumonia: always include treatment for atypical agents. Infect Dis Clin North Am. 2004;18:829-41.

Marrie TJ. Q fever pneumonia. Curr Opin Infect Dis. 2004;17:137-42.

Madariaga MG, Rezai K, Tenholme GM, et al. Q fever: a biological weapon in your backyard. Lancet Infect Dis. 2003;3:709-21.

Kovacova E, Kazar J. Q fever – still a query and underestimated infectious disease. Acta Virol. 2002; 46: 193-210.

Maltezou HC, Raoult D. Q fever in children. Lancet Infect Dis. 2002; 2:686-691.

INTERNET

Cleveland KO. Q Fever. Emedicine. Updated June 4, 2019. https://emedicine.medscape.com/article/227156-overview Accessed May 11, 2022.

Q Fever. Orphanet. Updated Jan 2014. https://www.orpha.net/consor/cgi-bin/Disease_Search.php?lng=EN&data_id=8529&Disease_Disease_Search_diseaseGroup=Q-fever&Disease_Disease_Search_diseaseType=Pat&Disease(s)/group%20of%20diseases=Q-fever&title=Q%20fever&search=Disease_Search_Simple
Accessed May 11, 2022.

Mayo Clinic for Medical Education and Research. Q Fever. Updated January 18, 2011. https://www.mayoclinic.com/health/q-fever/DS00960 Accessed May 11, 2022.

Centers for Disease Control and Prevention. Q Fever. Updated January 18, 2011. https://www.cdc.gov/qfever/index.html Accessed May 11, 2022.

Mayo Clinic Laboratories. Q Fever. https://www.mayocliniclabs.com/test-catalog/overview/62248#Clinical-and-Interpretive Accessed May 11, 2022.

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The information provided on this page is for informational purposes only. The National Organization for Rare Disorders (NORD) does not endorse the information presented. The content has been gathered in partnership with the MONDO Disease Ontology. Please consult with a healthcare professional for medical advice and treatment.

GARD Disease Summary

The Genetic and Rare Diseases Information Center (GARD) has information and resources for patients, caregivers, and families that may be helpful before and after diagnosis of this condition. GARD is a program of the National Center for Advancing Translational Sciences (NCATS), part of the National Institutes of Health (NIH).

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Orphanet has a summary about this condition that may include information on the diagnosis, care, and treatment as well as other resources. Some of the information and resources are available in languages other than English. The summary may include medical terms, so we encourage you to share and discuss this information with your doctor. Orphanet is the French National Institute for Health and Medical Research and the Health Programme of the European Union.

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