Q fever is a disease caused by a bacterium known as Coxiella burnetii ( C. burnetii ). It is a zoonotic disease, which means that the bacteria naturally exist in animals, called the natural reservoir. Cattle, sheep, and goats are the main natural reservoirs of C. burnetii , but the bacteria have been noted in a variety of other animals, including other species of livestock and domesticated pets. C. burnetii is found worldwide. It does not normally cause disease in animals, but it has been associated with miscarriage in some animals, especially livestock.
Q fever does occur in people, but it is not adequately reported to health officials by doctors, making it difficult for scientists to reliably measure how many cases of Q fever have actually occurred worldwide. In the United States, Q fever outbreaks have resulted mainly from work-related exposure among veterinarians, meat processing plant workers, sheep and dairy workers, livestock farmers, and researchers at facilities that house sheep. Approximately 2-3 Q fever cases are reported annually in New York City.
Exposure to C. burnetii does not always lead to illness. Only about half of all people infected with C. burnetii become ill. In those who do, Q fever often begins with sudden onset of one or more of the following: high fever (up to 104-105° F), severe headache, fatigue, muscle pain, confusion, sore throat, chills, sweats, dry cough, nausea, vomiting, diarrhea, abdominal pain, and chest pain. Fever usually lasts for 1-2 weeks. Weight loss can occur and last for some time. A majority of Q fever patients also have abnormal test results, indicating their liver is not functioning correctly. Some will develop inflammation of the liver (hepatitis) and others may get lung infections (pneumonia).
In general, most people with Q fever recover to good health within a few weeks without treatment. Although uncommon, some people with untreated infection can remain ill for months, which is called chronic Q fever. This is a much more serious and more difficult to treat disease and can involve severe heart infections. Patients with pre-existing heart valve disorders, transplant recipients, patients with cancer, and those with chronic kidney disease are at greater risk of developing chronic Q fever. Of the 1 to 2 percent of people with Q fever who die of the disease, most had chronic infections of the heart.
Symptoms of Q fever usually occur within 2-3 weeks of exposure, although some people get ill as long as 6 weeks later. Persons who were exposed to a large number of C. burnetii may become ill in a shorter amount of time than persons who were exposed to fewer organisms.
In the United States, Q fever outbreaks have resulted mainly from work-related exposure among veterinarians, meat processing plant workers, sheep and dairy workers, livestock farmers, and researchers at facilities that house sheep and especially in persons who have had contact with infected goats, sheep or cows that have recently given birth. Non-work-related infections also can take place. For example, contaminated dust can be carried long distances from farms by the wind and cause infections if inhaled.
Less commonly, milk or milk products can be naturally contaminated with the organism, and if the food item is not pasteurized, the bacteria can then cause infection after the food is consumed. On rare occasions, ticks that first fed on infected animals can then transmit the infection to people.
C. burnetii is excreted in milk, urine, and feces of infected animals. Extremely high numbers of the bacteria are shed during birthing (within the birth fluids and the placenta). C. burnetii forms unusual spore-like structures that are highly resistant to environmental conditions, including heat, drying, and many common disinfectants. These characteristics enable the bacteria to survive for long periods (up to 120 days) in the environment. C. burnetti is easily spread by aerosols; airborne particles can travel a half-mile or more.
Humans most often become infected by breathing in the bacteria through airborne barnyard dust contaminated by dried birth fluids, placental material, or waste of infected herd animals. In rare instances, transmission has occurred by tick bite. Humans are often very susceptible to the disease, and only a few bacteria may be required to cause infection. Fortunately, spread of the disease from person to person only occurs rarely.
Usually, Q fever is not contagious. Rarely, infection has been transmitted from one person to another by blood transfusion or bone marrow transplant. An obstetrician may have been infected by an infected patient when delivering her baby. Sexual transmission also may occur rarely.
Most often, antibody tests are done on blood samples to determine whether a person has been infected by C. burnetii . More specialized laboratory tests, such as polymerase chain reaction (PCR), also can be conducted when necessary.
Q fever typically is treated with a common antibiotic. Treatment is most effective when started within the first three days of illness.
Complications related to chronic Q fever (such as damaged heart valves) are much more difficult to treat effectively and often require the use of more than one drug. Surgery to replace damaged heart valves may be required in some cases.
There are no Q fever vaccines commercially available in the United States.
Many federal, State, and City agencies-including the New York City Health Department has been working together for several years to prepare for the detection and response to a bioterrorist event in New York City. In cooperation with other emergency response agencies, the Health Department has set in place systems that improve our ability to detect and respond to public health emergencies caused by the intentional release of a biological agent.
For more information about Q fever, visit the CDC Website .