Q fever is an acute illness often accompanied by pneumonia which results from infection with a form of Rickettsia. The first human cases of the disease were observed in Australia in 1933. Since they originated in Queensland, the infection was named “Q fever.” Now a similar organism has been isolated from ticks captured in Montana and cases have been found in other areas of the United States.

Human beings are highly susceptible to Q fever; from 25 to 40 per cent of those exposed may be attacked by the disease. The condition was found much more often in Australia among people exposed to cattle. Before 1946 the disease was rare in the United States but has now been found particularly in epidemics in stockyards such as the one in Amarillo, Texas, in Chicago, and among dairymen in Los Angeles county. Workers in research institutes have frequently been infected.

From twelve to twenty-six days after exposure, the disease comes on with symptoms like those seen in other Rickettsial diseases. The two striking features that make Q fever different from other infections with Rickettsia is the absence of any characteristic rash and the almost invariable presence of pneumonia. However, pulmonary symptoms are often mild or absent. About one-half the patients have aches in the chest. X-ray of the chest shows that the lungs have been infected in at least 90 per cent of the cases.

Q fever may be confused with primary virus pneumonia, with tuberculosis, with psittacosis or infected bird fever, and must also be distinguished from ordinary influenza, sinusitis, undulant fever, dengue, and other Rickettsial infections.

Here again aureomycin, chloromycetin, and terramycin have been found useful in treatment. Relapses are rare. Most of the patients recover. Thus far only some eight or ten deaths have occurred among perhaps 1,000 cases that have been reported in medical writings.

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When living organisms such as germs or viruses invade the human body, the tissues of the body undergo changes which help them to resist the poisons of the invader. By this reaction the tissues become immune to the poisons. Much depends on the virulence of the infections, the total number of germs invading, the place where they enter the body, the tissues or structures where they settle and grow. If you are susceptible to the infection, it will attack you; it may even overcome you. If you are resistant, the tissues of your body may develop antibodies which will overcome the germs or viruses or their poisons.

Certain environmental conditions may increase or lower your resistance to infection. Chilling of the body, excessive fatigue, absence of some essential nutritional substance, as proteins, or mineral salts or vitamins, or the presence of another disease at the same time may modify the resistance of the body to an invader.

The chemical composition of the invading organism may be significant in the way in which the body responds to it. An invading substance is known as an “antigen.” Usually the response of the body to an invading germ is specific against that germ or against that type of germ. Bacteria may contain a number of antigenic substances, against each of which the body will rebuild resistance. An example of an antibody against infections is the immune globulin. This is a protein substance found in blood, in which we now know are accumulated substances that help to resist various infections such as those of measles or poliomyelitis. In man, most of the antibodies are found in the immune globulin of the blood. The amount of antibody that develops is also governed by such factors as the amount of infectious material that gets into the body. The doctors find that they can help you build resistance by repeatedly injecting small doses of an infecting substance. We know that a child gets resisting substances from its mother in her blood at the time of birth and in the first material that comes from the breast when the child begins to nurse. This is called “colostrum.” The amount of antibodies may be unfavorably affected by starvation, exposure, reduced protein intake, alcoholism, or other poisoning.

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