Q fever

Page last reviewed: 13/07/2011

Q fever is a bacterial infection caused by the coxiella burnetii bacteria. It causes flu-like symptoms such as a high temperature, muscle pain and headaches. Read more about the symptoms of Q fever

In most people, the symptoms of Q fever will get better without treatment within two weeks. Antibiotics may be recommended if your symptoms are severe or do not improve. A less common, long-term form of Q fever requires antibiotics for several years. Read more about treating Q fever.

The 'Q' in Q fever stands for 'query'. This is because when the infection was first indentified, its cause was unknown. The cause is now understood but the name has remained the same.

Catching Q fever 

Q fever is spread to humans from animals, most commonly livestock such as sheep, goats and cattle. Very rarely, it can spread directly from human to human, usually during sexual intercourse. Read more about the causes of Q fever.

In Ireland, people who are most at risk of getting Q fever are those whose occupation brings them into close contact with livestock, including:

  • farmers
  • stablehands
  • abattoir workers
  • meat packers
  • veterinarians

In Ireland, around 17 cases of Q fever were reported in 2009. However, the actual figure may be much higher because Q fever often causes only mild symptoms that can be mistaken for flu.

Q fever is more common during the lambing season (around January to April), but can occur at any time of year. It is also more common in agricultural areas.

Types of Q fever

There are two main types of Q fever:

  • the most common and least serious type is called acute Q fever
  • the less common but more serious type is called chronic Q fever

Acute Q fever

Acute means short-term. Acute Q fever causes flu-like symptoms that last for a couple of weeks. Less commonly, acute Q fever can cause mild pneumonia (inflammation of the lungs), and mild hepatitis (inflammation of the liver).

Chronic Q fever

Chronic means long-term. In some cases, the symptoms of Q fever can last for six months or longer. This is called chronic Q fever. People with chronic Q fever will need to take antibiotics for at least three years to prevent the infection from reoccurring.

It is also possible for chronic Q fever to cause inflammation of the inner lining of the heart (endocarditis). Endocarditis is potentially very serious. Left untreated, it can affect the normal workings of the heart and lead to heart failure. With treatment, it is estimated that less than 1 in 10 people with endocarditis caused by Q fever will die. 


Useful Links



There is no vaccine for Q fever available in Ireland

Page last reviewed: 13/07/2011

Acute Q fever

Q fever is usually a short-term (acute) condition.

The symptoms of acute Q fever usually develop two or three weeks after the initial infection, although it can be as little as two days or as long as 40 days after. The time it takes for symptoms to develop after infection is known as the incubation period. Symptoms include:

  • high temperature (fever) of 38°C (100.4°F) or over
  • severe headaches
  • muscle and joint pain
  • sweats
  • sore throat
  • sensitivity to light
  • weight loss
  • a skin rash (less commonly)

These symptoms can come on quite suddenly and usually last up to two weeks.

In a few cases, acute Q fever can also cause pneumonia (inflammation of the lungs) and hepatitis (inflammation of the liver).

The pneumonia caused by Q fever is usually mild.

Symptoms include:

  • a dry cough
  • a sharp chest pain that is made worse by breathing deeply, coughing or laughing 

As with pneumonia, the hepatitis caused by Q fever is usually mild and many people will experience no obvious symptoms. Yellowing of your skin and the whites of your eyes (jaundice) is rare.

Chronic Q fever

In some cases, Q fever can become a long-term (chronic) condition. In chronic Q fever, the symptoms can last six months or longer after an acute Q fever infection. You may feel tired and generally unwell for months. 

In a few rare cases, chronic Q fever can cause inflammation of the inner lining of the heart (endocarditis). This is more likely to occur if you already have damage to your heart valves, or if you have had heart bypass surgery.

Endocarditis can cause the following symptoms:

  • chills
  • night sweats
  • fever
  • shortness of breath
  • a cough
  • unexplained weight loss

Read more about endocarditis.

Q fever in pregnancy

If you catch Q fever while you are pregnant, it often causes no symptoms. However, it can affect your unborn baby whether you experience any symptoms or not. It can cause:

  • your baby to be born early
  • your baby to have a low birth weight
  • a miscarriage or stillbirth



Page last reviewed: 13/07/2011

Q fever is caused by bacteria known as coxiella burnetii (or c. burnetii). The bacteria are usually spread to animals by infected ticks. Samples of c. burnetii have been found in almost all types of animals, including reptiles and fish.

The most commonly affected animals, and those that pose the biggest risk to humans, are:

  • sheep
  • cows
  • goats
  • domesticated pets, such as dogs, cats and guinea pigs

Most animals with Q fever do not experience any symptoms, so it can be difficult to tell if an animal is infected. However, the bacteria can cause an increase in miscarriages among an infected herd of cows or flock of sheep.

The bacteria can be released by an infected animal through its:

  • milk
  • blood
  • urine
  • stools (faeces)
  • fluids and products produced during birth, such as the afterbirth (placenta)

Birth by-products pose the greatest risk because they contain a high number of c. burnetii bacteria. For example, it is estimated that one gram of infected placenta contains enough bacteria to infect 100 million guinea pigs with Q fever.

How Q fever is spread to humans

Q fever can be spread to humans in a number of different ways. The c. burnetii bacteria are tough and can survive in the outside environment for up to six months. They can spread through:

  • breathing in small particles released by infected animals, particularly when animals are being slaughtered or giving birth
  • breathing in small particles from contaminated soil, dust, hay, straw bedding or other substances
  • infected particles coming into contact with a cut on your skin or the white part of your eyes 
  • drinking unpasteurised milk from an infected animal (unpasteurised milk is milk that has not been treated with heat to kill off bacteria)

It is possible that a bite from an infected tick could lead to Q fever, but there have not been any recorded cases of this in Ireland.

Human to human transmission

It is possible, but very rare, to catch Q fever from another person.

Most experts believe that Q fever can only be transmitted from one human to another through:

  • sexual intercourse
  • by a pregnant woman passing on the infection to her unborn child

Chronic Q fever

It is unclear why some people go on to develop the long-term (chronic) form of Q fever. Most cases of chronic Q fever develop in people with a pre-existing health condition, which makes them more vulnerable to infections. These health conditions include:

coronary heart disease or congenital heart disease, particularly disease that affects the valves of the heart, such as narrowing of the valves (stenosis)

  • having previously had heart bypass surgery (coronary artery bypass graft)
  • kidney disease
  • cancers that affect the blood, such as lymphoma and leukaemia

Vulnerability to infection is higher in people who have a weakened immune system, caused either by a health condition, such as HIV or AIDS, or as a side effect of certain medical treatments, such as chemotherapy or long-term steroid use.

Useful Links

Page last reviewed: 13/07/2011

Q fever can be diagnosed using a blood test.

Blood test

If the c. burnetii bacteria that cause Q fever are present in your blood, your immune system (the body's natural defence system) will produce a type of protein called an antibody to kill them. A sample of your blood will be tested at a laboratory for the presence of these antibodies. The antibodies should show up two or three weeks after you have been infected.

A sample of your blood can also be tested after you have been treated to check that the antibodies have gone.

Further tests

If you develop inflammation of the lungs (pneumonia) or inflammation of the liver (hepatitis), you may have some further tests such as:

  • a chest X-ray to see how the infection has affected your lungs
  • liver function tests to see how well your liver is working


Useful Links

Page last reviewed: 13/07/2011

In most people, the symptoms of Q fever will get better without treatment within two weeks.

You may need treatment with antibiotics if your symptoms:

  • are severe
  • do not improve
  • return after your initial infection

Acute Q fever

If you have short-term (acute) Q fever, you may be prescribed doxycycline or tetracycline.

You will need to take these for 7-14 days and for at least three days after your fever has improved.

If you are prescribed antibiotics, it is important that you finish the whole course, even if you feel better. This will ensure that all the bacteria have been killed, preventing the infection from reoccurring.

Chronic Q fever

Long-term (chronic) Q fever can be difficult to treat because the c. burnetii bacteria, which cause Q fever, can be resistant to antibiotics. This means the antibiotics can't kill them.

You will need to take a combination of antibiotics, such as doxycycline and chloroquine.

It is recommended that you take these for at least three years. However, the infection returns in more than half of people.

You may need to have blood tests every three to six months while you are being treated to check that the treatment is working.

If you have inflammation of the lining of your heart (endocarditis), you will need to be treated in hospital. Read more about treating endocarditis.

Useful Links leave hpa link

Pregnancy and breastfeeding

If you are pregnant or breastfeeding and have Q fever you may be referred to a doctor who specialises in infectious diseases. They will advise you about your treatment.

Page last reviewed: 13/07/2011

At work

If you work with animals, your employer has to ensure that preventative measures are in place to lower your risk of getting Q fever. For example, they must ensure that all animal birth products are disposed of properly and that access to infected animals is restricted.

You can also reduce your risk of getting Q fever by not drinking unpasteurised milk and dairy products, and by not touching anything that may have been in contact with animal blood, stools (faeces) or urine.

People who are particularly vulnerable to infection should avoid occupations that carry a high risk of exposure to Q fever. These occupations are:

  • livestock workers
  • abattoir workers
  • meat packers
  • farmers
  • vets and veterinary assistants

People who are vulnerable to Q fever include:

  • those with a history of heart valve disease
  • those with a weakened immune system
  • pregnant women


If you are pregnant, avoid contact with sheep and lambs during the lambing season.

Pregnant women who come into close contact with sheep during lambing may risk the health of their unborn child because Q fever (as well as other sheep-borne infections) can cause miscarriages or stillbirths.

To avoid the possible risk of developing infections, pregnant women are also advised to avoid the following:

  • helping lamb or milk ewes
  • contact with aborted or newborn lambs or with the afterbirth
  • handling clothing, boots and other items that have come into contact with ewes or lambs

Useful Links

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

Browse Health A-Z