Bacteria, Epidemiology, Infectious Diseases, Microbiology, Vaccines

Q-Fever 101: All About This Neglected Zoonotic Disease

Author Chandana Balasubramanian , 28-Feb-2024

Q fever may not be well known, but it is a bacterial disease that can be used as a biological weapon. Coxiella burnetii, the causative agent, infects sheep, cattle, and other domestic animals and can spread to humans, even when the animals do not show symptoms of the infection!


C.burnetii is hardy, can survive in harsh environments, and is highly resistant to high temperatures, pressures, and many common disinfectants. Adding to these complications, the bacteria is regarded as a potential agent of bioterror. 


This makes it important to be vigilant and prioritize surveillance and timely reporting of Q fever outbreaks.


This article covers the basics of Q fever, including the history, epidemiology, biology, transmission, symptoms, diagnosis, treatment, and ways to prevent Q fever infections.



Other names for Q fever include Nine Mile fever, Australian Q fever, and Balkan influenza.

Q fever was first discovered in 1935 in workers in slaughterhouses in Australia. Dr. Derrick is credited with discovering the bacterial infection, although the pathogen was still unknown at the time. Because doctors did not know what caused the disease and had ‘queries,’ Q fever was known as query fever.

Around the same time, in Nine Mile, Montana, in the United States, a pathogen was isolated and named the ‘Nine Mile agent.’ Eventually, a person in Nine Mile, Montana, fell ill when handling Q fever samples shipped from Australia, establishing a potential link between Q fever and the Nine Mile fever.



Q fever is found around the world. It can infect various hosts, including ticks, fish, birds, sheep, goats, cattle, other ruminants, and humans. 

People most at risk of developing Q fever work with cattle and sheep. This includes slaughterhouse workers, veterinarians, farm workers, and meat packers.  

Notable Q fever outbreaks

  • 1948: Germany: 1,500 cases reported near Tubingen.
  • 1980: Czech Republic: 526 cases reported in employees of a cotton production plant at Staré Město.
  • 1982-1985: Bulgaria: 725 cases near Knezha town.
  • 2007-2011: Netherlands: 4,107 cases reported with 24 deaths in the Noord-Brabant and Den Bosch region. As a result, 62,500 animals were culled in over 94 farms. By 2016, total mortality, including from patients with chronic Q fever, had risen to 74 cases. This is the largest Q fever outbreak reported so far.


For a comprehensive list of Q fever outbreaks and more information, visit GIDEON


How does it spread?

The bacterium Coxiella burnetii has a remarkable ability to survive in even tough environments, making its transmission to humans more likely under certain conditions. 

Here is how Q fever can spread to humans:

  • Inhalation of aerosolized bacteria: The most common way that Q fever spreads to humans is by inhaling contaminated air containing the bacteria. Infections can happen on farms, in slaughterhouses, and anywhere close contact with animals or animal products occurs. The risk is particularly high after the delivery of infected animals when the concentration of bacteria in the environment spikes.
  • Exposure to high concentrations of bacteria: Infected animals shed the bacteria in their urine, feces, and milk. These bodily fluids can contain high concentrations of the bacteria, especially after the animal has given birth. The bacteria can survive for extended periods in the environment, increasing the risk of human exposure.
  • Eating unpasteurized dairy products: Unpasteurized dairy products can increase the risk of humans getting sick from Q fever.
  • Bioterrorism: Q fever can be aerosolized and used as a bioterror agent. As a bioterror agent, Q fever may not cause widespread deaths, but it may lead to disabling disease among many. 


Biology of the disease

C.burnetii is an intracellular, gram-negative bacterium. Q fever primarily infects humans through breathing in air or dust containing the bacteria. 

Once inhaled, C.burnetii travels to the lungs, where it can infect alveolar macrophages, an immune cell responsible for engulfing and digesting pathogens. 

The bacteria blocks the function of these macrophages and then uses the host’s cellular machinery to replicate and spread to the rest of the body, infecting the liver, spleen, and heart.

Chronic Q fever can cause infective endocarditis, an inflammation of the heart.



Q fever is caused by the bacterium Coxiella burnetii and can affect humans. 

According to the US CDC, Q fever symptoms include: 

  • High fever
  • Severe headache
  • General malaise
  • Muscle pain
  • Chills and/or sweats
  • Non-productive cough
  • Nausea, vomiting, or diarrhea
  • Chest pain
  • Abdominal pain
  • Tiredness


In chronic cases, which are less common, symptoms may include:

  • Endocarditis (an infection of the heart valves)
  • Persistent fevers
  • Fatigue
  • Weight loss


Symptoms usually appear 2 to 3 weeks after exposure to the bacterium. Many people infected with Coxiella burnetii may have mild symptoms or be asymptomatic and never know they were infected. 

People who have heart valve disease or are immunocompromised (for example, people who have HIV or cancer) may be at a higher risk of developing chronic Q fever.



Q fever is often misdiagnosed as an influenza or pneumonia-like infection because its symptoms are similar to many other diseases. Because of this, it is even more critical for healthcare providers to ask about patient history, including exposure to animals.

If patients let their healthcare providers know about any recent contact with sheep, goats, or cattle, the proper blood tests may help identify Q fever accurately.



Most people with Q fever recover without any treatment. However, antibiotics may be prescribed for those with more severe or prolonged symptoms.



The best way to prevent Q fever is to:

  • Consume pasteurized milk and other dairy products
  • Avoid or minimize interactions with animals, particularly when they are giving birth
  • Wearing gloves and masks can help protect against animal fluids when working with animals.


In Australia, a Q fever vaccine called Q-Vax for adults is recommended, particularly for at-risk people who work with animals.



Q fever is a bacterial infection that can be used in biological warfare. It is caused by C.burnetii, a hardy bacteria that can live in demanding environments, making it harder to kill. The zoonotic disease spreads to humans primarily from goats, sheep, and cattle. Although most people have mild or no symptoms, infections can lead to chronic Q fever, a more debilitating, longer-term illness.

People most susceptible to Q fever infections are those who work with animals. Unfortunately, there is only one Q fever vaccine, Q-Vax, which is used exclusively in Australia, even though Q fever is endemic worldwide. A vaccine that is available worldwide and safe hygiene practices when handling animals can go a long way in preventing Q fever outbreaks.


The GIDEON difference

GIDEON is one of the most well-known and comprehensive global databases for infectious diseases. Data is refreshed daily, and the GIDEON API allows medical professionals and researchers access to a continuous stream of data. Whether your research involves quantifying data, learning about specific microbes, or testing out differential diagnosis tools– GIDEON has you covered with a program that has met standards for accessibility excellence.

Learn more about more bacterial infections on the GIDEON platform.


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Chandana Balasubramanian

Chandana Balasubramanian is an experienced healthcare executive who writes on the intersection of healthcare and technology. She is the President of Global Insight Advisory Network, and has a Masters degree in Biomedical Engineering from the University of Wisconsin-Madison, USA.

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