Q fever or query fever is a disease caused by infection with Coxiella burnetii, a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including cats and dogs. The infection results from inhalation of a spore-like small-cell variant, and from contact with the milk, urine, feces, vaginal mucus, or semen of infected animals. Rarely, the disease is tick-borne. The incubation period is 9–40 days. Humans are vulnerable to Q fever, and infection can result from even a few organisms. The bacterium is an obligate intracellular pathogenic parasite. Signs and symptoms
Incubation period is usually two to three weeks. The most common manifestation is flu-like symptoms: abrupt onset of fever, malaise, profuse perspiration, severe headache, muscle pain, joint pain, loss of appetite, upper respiratory problems, dry cough, pleuritic pain, chills, confusion, and gastrointestinal symptoms, such as nausea, vomiting, and diarrhea. About half of infected individuals exhibit no symptoms.During its course, the disease can progress to an atypical pneumonia, which can result in a life-threatening acute respiratory distress syndrome, whereby such symptoms usually occur during the first four to five days of infection.Less often, Q fever causes (granulomatous) hepatitis, which may be asymptomatic or become symptomatic with malaise, fever, liver enlargement, and pain in the right upper quadrant of the abdomen. Whereas transaminase values are often elevated, jaundice is uncommon. Retinal vasculitis is a rare manifestation of Q fever.The chronic form of Q fever is virtually identical to endocarditis (i.e.
They have shown that approximately 1 in 3 cattle farms and 1 in 4 sheep or goat farms are infected. However, there are wide variations between studies and countries. In China, Iran, Great Britain, Germany, Hungary, the Netherlands, Spain, the US, Belgium, Denmark, Croatia, Slovakia, the Czech Republic, Serbia, Slovenia and Jordan, for example, it has been shown that more than 50% of cattle herds were infected with Q fever.Infected animals shed the bacteria by three routes: genital discharge, faeces and milk. Excretion is greatest at the time of parturition or abortion and placentas and aborted fetuses are the main sources of bacteria, particularly in goats. As Coxiella burnetii is small and resistant in the environment, it is easily airborne and can be transmitted from one farm to another, even if it is several kilometres away. Control
Biosecurity measures
Based on the epidemiological data, biosecurity measures can be derived:
The spread of manure from infected farm should be avoided in windy conditions
The level of hygiene must be very high during parturition and fetal annexes and fetuses must be collected and destroyed as soon as possible

Medical measures
A vaccine for cattle and goats exists. It reduces clinical expression such as abortions and decreases excretion of the bacteria by the animals leading to control of Q fever in herds.In addition, vaccination of herds against Q fever has been shown to reduce the risk of human infection. References
External links

Q fever at the CDC
Coxiella burnetii genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID