The interval between inhalation of the organism (ie. exposure) and onset of the illness may range from 14 to 60 days, depending on the intensity of exposure to the organism. Individuals exposed to the highly infective products of conception have been observed to have the shortest incubation period and the most severe illness. The usual incubation period is 19 to 21 days.
Signs and Symptoms
These include sudden onset of acute fever, chills, profuse sweating, cough, severe headache, muscle pains and weakness. It is not unusual for a diagnosis of influenza to be made during the initial stages of the illness. As the symptoms could be the body’s response to any number of invading organisms or viruses, a series of laboratory blood tests are required to confirm a diagnosis of Q fever.
Individual responses to this infection, as with all infections, will vary. For some, there will be no illness and a past exposure may only become apparent when antibodies are detected ‘in a blood sample or there is a positive skin test reaction. Others may have symptoms for a few days, dismissing the illness as ‘viral’ or they could just feel ‘off colour’ and, as such, may not seek medical attention.
Typically though, the fever lasts seven to ten days and is accompanied by excessive sweating (warranting many changes of clothes and bed linen), nausea, vomiting, diarrhoea, and anorexia. There is often weight loss of 6 to 12 kilograms if the acute episode is prolonged. For some, the recovery period will be protracted following an acute infection.
On occasions, other patterns of the disease can be so debilitating that hospitalisation is required. As the organism is circulated through the body in the blood stream, any organ system can become involved including the central nervous system, lungs, liver, kidney, testes and heart muscle and tissue. Persons with pre-existing heart valve damage resulting from disease or congenital malformation could be at risk of developing endocarditis.
Death from acute Q fever is very rare and occurs mainly in the elderly or those whose health is compromised by illness or disease.
Generally, the illness will last one to six weeks with most patients gaining a life-long immunity to further infection.