Q fever

Q fever is a zoonosis caused by a highly infectious microorganism: Coxiella burnetii.  That organism is very resistant to heat, pressure and drying. It can persist for months under the form of spores, a long time after the infectious outbreak is over. Q fever has been described for the first time in Australia. It is widespread worldwide.

Goats, cattle and sheep are the primary reservoir of Q fever. C. burnetii can be found in faeces, urine, milk and tissue (mainly placenta). You can also find it in arthropods, rodents, other mammals and birds that can all play a role in human infection. The microorganism is eliminated by urine and faeces of contaminated animals. It can mainly be found in blood and tissues of birth products. During pregnancy, the organism accumulates in the placenta. During birth, considerable quantities of Coxiella organisms are thus widespread in nature.

The disease mainly occurs in veterinarians, meat merchants and farmers. Outbreaks have started in animal farms, in meat packaging industries and in laboratories that use sheep for research.

Contamination modes

• Humans are infected by inhalation of infected drops present in the dust of contaminated zones.
• Infection by ingestion of contaminated food or non-pasteurized milk is rare.
• Infection is rarely due to tick bites.
• Contamination from human to human by infection due to drops has not been reported.
• Transmission from human to human is rare but contaminated clothes can be a cause of infection.

Intentional propagation:

• It is very likely that propagation occurs under the form of a cloud of Coxiella spores that would be inhaled by victims. The organism is easily propagated by spray and is very stable and very resistant to heat and to drying.
• The potential of C. burnetii as biological weapon is directly linked to the high degree of contagiousness of the germ.
• It is assessed that 50 kg of C. burnetti under the form of dried powder could cause as many victims as an equal quantity of anthrax or organisms propagating tularaemia.

Q fever symptoms

C. burnetti provokes disease symptoms only in humans. Only 50 % of infected people develop a syndrome. The disease is rarely fatal (less than 1 %). 

• The incubation period varies between 10 to 40 days.
• The disease can start in a sudden or insidious way with fever, shaking, stiffness and violent headaches.
• Those symptoms are often accompanied by malaise, tiredness, myalgia, and anorexia sometimes leading to acute loss of weight.
• Cough appears later on sometimes with retrosternal pains.
• Central nervous system can be attacked, mainly under the form of visual and auditory hallucinations, diplopia, and disarthria.

Treatment

Most patients totally recover without any treatment after a few months. However antibiotics shorten the disease duration. Doxycycline is the best treatment in case of acute Q fever. Antibiotics therapy is mostly effective when it is started within the first three days of the disease.

Alarm signs indicating a potential intentional propagation by aerosol

If, on a period of one or two weeks, a relatively high number of persons develops a non-specific febrile syndrome which, in one case out of four is associated with pulmonary symptoms, the possibility of intentional propagation of Coxiella burnetii has to be taken into account.