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Q fever: a tough zoonosis
  1. Conall McCaughey, BSc, MD, FRCPath
  1. Royal Hospitals, Belfast HSC Trust, Grosvenor Road, Belfast BT12 6BA, UK
  1. e-mail: conall.mccaughey{at}

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Q FEVER was first recognised as a clinical entity in an outbreak of respiratory illness in abattoir workers in Brisbane, Australia, by Derrick in the 1930s (Derrick 1937). The ‘Q’, which stands for ‘query’, was intended, at the time, as a temporary terminology while the cause was investigated. However, the name stuck and almost 80 years later, despite a mass of literature on the disease and the causal organism Coxiella burnetii, the human disease is still known as Q fever. The agent has a worldwide distribution with the notable exception of New Zealand and possibly parts of Oceania.

Clinical presentations in people vary widely. Most cases are asymptomatic or mild but clinically apparent infections typically present with fever and pneumonia which can be severe and result in hospitalisation. A small proportion of human cases go on to develop chronic infection usually manifesting as endocarditis, especially in patients with previously damaged or prosthetic heart valves. Such chronic infection is difficult to treat and has a substantive mortality.

Almost all human Q fever infections are zoonotic in origin with human-to-human transmission being only occasionally recognised (Miceli and others 2010). Ruminants are considered to be the main source of human infection; however, the role of wildlife, including rodents and ticks, as a reservoir of infection remains unresolved (Cutler and others 2007).

The causal organism was first isolated in guinea pigs from human blood by Burnet and Freeman (1937) in Australia and from ticks by Davis and Cox (1938) in the USA. Hence the genus …

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