On this page
- Key messages
- Notification requirement for Q fever
- Primary school and children’s services centre exclusion for Q fever
- Infectious agent of Q fever
- Identification of Q fever
- Incubation period of Q fever
- Public health significance and occurrence of Q fever
- Reservoir of Coxiella burnetii
- Mode of transmission of Coxiella burnetii
- Period of communicability of Q fever
- Susceptibility and resistance to Q fever
- Control measures for Q fever - preventive measures
- Outbreak measures for Q fever
Key messages
- Q fever is a zoonotic bacterial disease that can cause acute flu-like illness and long term complications.
- Q fever is spread to humans from infected animals, animal products and animal waste, most commonly cattle, sheep and goats.
- People who work with animals, animal products and animal waste are at increased risk of Q fever, particularly those in high-risk occupational groups.
- Vaccination is recommended for workers in high-risk occupational groups.
- Early diagnosis and antibiotic treatment are important to reduce the severity of illness and risk of long term complications.
- Q fever is a routine notifiable condition and must be notified by medical practitioners and pathology services in writing within 5 days of diagnosis to the Department of Health.
Notification requirement for Q fever
Q fever infection is a ‘routine’ notifiable condition and must be notified by medical practitioners and pathology services in writing within 5 days of diagnosis to the Department of Health.
This is a Victorian statutory requirement.
Primary school and children’s services centre exclusion for Q fever
Exclusion is not applicable.
Infectious agent of Q fever
Q fever is caused by Coxiella burnetii (C. burnetii), an obligate intracellular Gram-negative coccobacillus. It is highly infective and can survive in the general environment, such as dust and soil, for months and years.
Identification of Q fever
Clinical features
Many people with Q fever have no symptoms or mild symptoms (almost 60 per cent of infections). Q fever can present as an acute or chronic illness.
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Acute Q fever can present as a flu-like illness with symptoms of fever, chills, sweats, severe headache (especially behind the eyes), weakness, anorexia, myalgia and cough. Sometimes it can be associated with a transient mild rash. Most people make a full recovery.
Other acute presentations include pneumonia and hepatitis, which may be granulomatous. Rarely (in less than 1 per cent of infections), acute Q fever can lead to complications of pericarditis, myocarditis, meningoencephalitis, encephalomyelitis and orchitis.
Q fever in pregnancy can lead to abortion, premature delivery, or low birth weight.
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Chronic Q fever can occur from one month to several years after acute illness, and sometimes even without a history of acute illness, as a result of persistent C. burnetii infection in the host after primary infection.
Chronic Q fever may present as one of three major forms depending on the focus of infection:
- Endocarditis, which is the most serious form and is fatal if left untreated. Risk factors include underlying valvular heart disease and valvular prosthesis.
- Osteoarticular infections, which can affect bone and joints at multiple locations.
- Vascular infections, which most frequently affect the thoracic and abdominal aorta and is associated with high mortality. Risk factors include underlying aneurysms and vascular grafts.
People at increased risk of developing chronic Q fever infection include those who are immunosuppressed, pregnant women and those with pre-existing valvular heart disease, valvular prosthesis, aneurysms or vascular grafts.
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Q fever fatigue syndrome refers to systemic symptoms that fail to recover more than 12 months after the acute illness. Typical features include profound fatigue, arthralgia, myalgia, concentration and memory problems, sleeping problems, sweats and headaches.
It is the most common sequela of acute Q fever in Australia, occurring in approximately 10 to 15 per cent of people with acute infection.
Diagnosis
Q fever is usually diagnosed by:
- polymerase chain reaction (PCR) testing, and
- serology with paired (acute and convalescent) samples
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C. burnetii can be detected in blood on PCR testing for up to 2 weeks after illness onset. It is highly sensitive in detecting early infection. However, a negative result alone does not exclude a diagnosis of acute Q fever, and serological testing should be completed for all patients.
Paired (acute and convalescent) serum/blood samples should be collected 2 to 3 weeks apart in all patients suspected of Q fever, even if the patient has recovered This is because single serology tests (EIA, CFT, or IFA) are unable to distinguish between acute, past and chronic infections, and antibody detection is highly dependent on the timing of specimen collection. Indirect immunofluorescence assay (IFA) is the reference method, but the complement fixation test (CFT) and enzyme immunoassays (EIA) are also used to support diagnoses.
In addition to positive PCR, acute Q fever diagnosis can be confirmed by observing seroconversion or a 4-fold or greater increase in C. burnetii antibody titre to phase II antigen by CFT or by IFA assay in paired sera.
The diagnosis is also suggested by:
- the presence of IgM antibody to burnetii phase II antigen, or
- a single convalescent IgG antibody to phase II antigen > 1:128 by IFA assay.
Q fever IgM may persist for many months after infection; hence, its presence does not necessarily confirm the diagnosis.
If Q fever antibodies are present within 3–4 days of the onset of symptoms, this is more likely to indicate past exposure than recent infection.
People with acute Q fever should have serial antibody titres over time to monitor for the risk of developing chronic Q fever and to allow early interventions.
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PCR testing is less sensitive in chronic Q fever. Suitable specimens include blood and biopsy specimens of focally infected tissues such as heart tissue, bone or vascular graft.
Diagnosis of chronic Q fever is usually made by detection of C. burnetii by PCR of heart tissue, bone or vascular graft and can be suggested by detection in blood. It is also suggested by the presence of IgG antibody to C. burnetii phase I antigen > 1:1024 by IFA assay.
IgA class antibody to phase I antigen is highly suggestive of Q fever endocarditis.
Cross-reactive serologies have been extensively reported for pathogens such as Legionella spp., Mycoplasma pneumoniae, Rickettsia spp., Chlamydia spp., parvovirus, Bordetella pertussis, Epstein–Barr virus and cytomegalovirus. Almost 50 per cent of cases have cross-reactive serology for Bartonella spp.
The interpretation of Q fever serology results can be challenging. Clinicians should seek advice from their local infectious diseases service or microbiologist as required.
Incubation period of Q fever
The incubation period is typically 14 to 21 days, depending on the size of the infectious dose but can range from 4 days to 6 weeks.
Public health significance and occurrence of Q fever
Q fever is a zoonotic disease that occurs around the world. The true incidence of disease is likely greater than that reported because of asymptomatic and subclinical infection, as well as limited clinical suspicion and testing.
Q fever usually has low mortality but can be associated with significant morbidity. It most commonly occurs in people in high-risk occupational groups who work with animals, animal products and animal waste (including farm animals such as cattle, sheep and goats and some wild and domestic animals). Outbreaks have been reported occasionally in Australia, generally related to occupational and/or environmental exposures.
Reservoir of Coxiella burnetii
C. burnetii is commonly found in cattle, sheep, and goats but can also found in a wide range of domestic and wild animals including camels, llamas, alpacas, rodents, cats, dogs, horses, rabbits, pigs, buffalo, foxes, some birds, kangaroos and bandicoots.
Infected animals shed C. burnetii in milk, urine, faeces and birth products. It can survive for long periods in the environment (more than 1 month on fresh meat, almost 9 months in wool, and 40 months in skim milk).
C. burnetii can survive in the general environment (such as dust and soil). It is resistant to a variety of harsh environmental conditions including elevated temperatures, desiccation, osmotic shock, UV light and chemical disinfectants.
Mode of transmission of Coxiella burnetii
Q fever is most commonly transmitted to humans through inhalation of dust or aerosols contaminated with bacteria from birth fluids, faeces, urine, or blood of infected animals in circumstances such as:
- animal birthing
- animal slaughter, skinning and meat processing
- herding
- shearing and wool processing
- work with animal manure
- transport of infected animals
- mowing in or through areas where there are livestock or wild animals
- veterinary procedures
Contaminated dust or aerosols may potentially travel considerable distances from the source to cause exposure.
- Q fever can also be transmitted through direct contact of broken skin with infected animal tissues and fluids or contaminated materials, including contaminated such as straw, wool, hides or the clothing of workers.
- Person-to-person transmission is very rare but can occur through blood transfusion or bone marrow transplant, vertical or perinatal transmission, autopsy of infected cadavers and sexual transmission.
- Foodborne: Drinking unpasteurised milk from an infected animal has been suggested as a possible route, but this has not been proven.
- Percutaneous route: infection can occur through subcutaneous and intramuscular inoculation, for example following cuts with contaminated knives in the abattoir.
- Vector-borne: C. burnetii has been detected in numerous tick species in Australia, but human infections from ticks have been infrequently documented, possibly through tick bites or inhalation of tick excreta
Period of communicability of Q fever
Person-to-person transmission is very rare.
Susceptibility and resistance to Q fever
People are at risk of Q fever following exposure if they have not been vaccinated or do not have immunity following recovery from previous infection.
People who work with animals, animal products and animal waste in high-risk occupational groups are at increased risk. Refer to the Better Health Channel webpage on Q for further information on these groups.
Previous infection may confer lifelong immunity. Antibodies are detectable for 3 to 5 years but may persist as long as 15 years.
Most cases are in male adults, but this is probably due to their higher frequency of occupational exposure rather than differential susceptibility.
Control measures for Q fever - preventive measures
Vaccination
Workers in high-risk occupational groups are strongly recommended to be vaccinated against Q fever. However, people who have previously had Q fever or have already received the Q fever vaccine should not be vaccinated due to the risk of adverse reactions (severe local reactions).
It is necessary to screen for previous exposure prior to vaccination. This involves:
- checking for a documented clinical history of Q fever or Q fever vaccination, and
- serology tests, and
- an intradermal skin test, read after 7 days.
Any positive result on screening precludes vaccination.
Vaccine immunity appears to last at least 5 years. Training is recommended for medical practitioners intending to conduct Q fever screening and vaccination. Boosters are not recommended because there is a risk of serious local adverse events in people with pre-existing immunity to Coxiella burnetii, obtained either through natural infection or vaccination.
Access to high-risk environments, such as abattoirs and meat-processing plants, should be restricted to immunised people. This includes visitors, contractors and delivery drivers. Workers in these environments should also be educated about the nature of the disease.
For more information on vaccination refer to the Q fever vaccination webpage and Australian Immunisation Handbook – Q .
Infection prevention and control measures
Individuals, companies and employers can take steps to reduce the risk of exposure to Q fever through workplace design and safe work practices.
Actions that can be taken to reduce exposure include, but are not limited to:
- Washing the hands and arms thoroughly in soapy water after any contact with animals
- Wearing a P2 respiratory mask (available from pharmacies and hardware stores) and gloves in handling and disposing of animal products, waste, placentas and aborted fetuses
- Keeping personal protective equipment (PPE) and contaminated clothing at the workplace and appropriately bagging and washing them on site where possible to reduce the risk of exposing non-vaccinated individuals outside the workplace
- Appropriately managing and disposing of animal products and animal waste to prevent spread of C.burnetii bacteria
- Minimising dust and aerosols in slaughter and animal housing areas
Control of case
Q fever infection is treated with antibiotics.
Acute Q fever generally requires treatment with doxycycline. Consult the current version of Therapeutic guidelines: antibiotic or your local infectious diseases service.
Chronic Q fever requires long-term combination antibiotic treatment , specialist input and potentially surgical treatment, for example cardiac surgery. Clinicians should seek advice on clinical management from an infectious diseases service.
Isolation is not necessary. Articles contaminated with blood, sputum and excreta should be disinfected using standard precautions.
Control of contacts
No specific measures are required for household contacts, although it is recommended that they do not handle potentially contaminated clothing from the case.
Vaccination during the incubation period does not prevent the disease. There is no evidence to support post-exposure antibiotic prophylaxis and it is not recommended.
Control of environment
If a clear source is identified, C. burnetii can be killed by:
- Heating to >63 degrees Celsius for 30 minutes
- hydrogen peroxide
- sodium hypochlorite (at concentrations of greater than 5 per cent)
- 2 per cent formaldehyde
- 1:100 dilution of household bleach
Outbreak measures for Q fever
All notified cases are investigated to ascertain the most likely source of exposure, identify and provide information to other people at risk of infection (the ‘co-exposed’), identify any other linked cases and ensure control measures are in place. If two or more cases are linked in time and place to a workplace, other staff should be assessed for immune status (if not already known) with antibody levels and skin testing. Non-immune staff should be excluded from the worksite until 15 days after vaccination.
WorkSafe Victoria will be notified by the Local Public Health Unit if there is a plausible occupational exposure uncovered in the investigation.
The role of the workplace health and safety regulator is to investigate and identify unsafe working conditions, make recommendations to the employer, monitor the control measures implemented and enforce compliance.
Further information on activities undertaken by WorkSafe can be found on the WorkSafe Q fever . Victoria is notified by the Local Public Health Unit if there is a plausible link to an animal source to potentially assist in environmental investigation.
Management of co-exposed persons
A co-exposed person is defined as anyone who may have experienced the same occupational, animal, or environmental exposures as the case, or who may have been exposed to contaminated items associated with the case.
Those workers/co-exposed persons with the same exposure that do not have immunity to Q fever should not visit the setting, enter high risk workplaces or perform work that exposes them to Q fever risks without wearing a properly fitted particulate respirator.
Vaccination and post exposure prophylaxis with antibiotics are not recommended.
Co-exposed persons should be advised to seek medical attention if they develop symptoms. Vaccination should be offered to persons in at-risk occupations.
Reviewed 17 December 2024