Tuberculosis is a deadly infectious disease that is caused by mycobacterium.
Tuberculosis may creep on insidiously and without warning. By the time the well-known, significant symptoms appear, the disease is well advanced. Cough, with production of sputum (probably blood-stained), and breathlessness occur only with a well-established disease. Generalised symptoms such as weight loss, fever and copious sweating are also indications of an advanced state of TB.
In the past in many cases (probably the majority), TB was detected during mass radiograph screenings, or if the patient happened to have a chest X-ray for some other purpose. At this stage, symptoms are usually totally absent. Sometimes situations call for a chest X-ray, such as a chest infection that is not responding to the usual forms of treatment within a reasonable period of time.
Left untreated, the lung substance is gradually destroyed as “caseating” lesions (wax-like material) develop in the diseased parts. The lung structure may become destroyed, thus reducing the amount of lung tissue available for the body’s respiratory requirements.
An unusual form of the disease, termed “miliary tuberculosis”, can occur in which there is a very fine spread of the disease throughout the lung substance. Even with radiography, these cases are sometimes missed by the experienced Xray interpreter.
Indeed, the situation has now been reached that practically anyone with active TB can be cured. It is merely a matter of time, and sticking to the recommended forms of medication. No longer are the long drawn-out forms of therapy of a few decades ago being used. Many persons can resume their usual activities, and live a relatively normal life. Also, their expected life span following a cure is about the same as that of the rest of the population.
In the unprotected situation, infants under the age of three years are particularly liable to infection. After this, there is relatively good protection in youngsters and adolescents. This also applies to young adults. Over the age of 40 years the male is much more likely to succumb to infection than the female. Many in the over-40-years age group were infected during their youth, and re-infections in this group are likely. Factors such as cigarette smoking may play a part in reactivation of the disease that has been dormant for many years.
Today, younger people are rarely exposed to infection. In many communities protection against TB is available in the form of the BCG vaccination, and large numbers have received this. Although the spread of the human strain of the TB germ is the most likely to infect other humans, the bovine (cow) strain may also play a part. However, in recent years with mass TB testing of dairy herds and pasteurisation of milk supplies, this source has largely been removed as a possible risk in most modern communities.
During the next 20 years there was another dramatic fall, to 4.6 per 100,000 males and to the low figure of 1.6 for females.
The first dramatic fall has been attributed to the massive improvement that occurred in the Western world in general with improved social and economic conditions.
Reduced overcrowding with better housing and improved sanitation and water supplies greatly improved the general level of living standards, and collectively they have proved to be effective in reducing the incidence of pulmonary tuberculosis.
The tubercle bacillus is freely shed from infected persons in the sputum that is coughed up from the lungs. This may persist for a long time, particularly if not exposed to the sunlight, which acts as a sterilising agent. This is the most common form of spread. Therefore, in times when overcrowding was the rule, it was very easy for persons to spread it readily to those in the nearby environment. The germ is spread in the air by droplet infection. Thus, if an infected person coughs, millions of germs may be sprayed into the surrounding environment, and anyone present is at risk.
With modern housing and less crowded situations, the risk of all this has largely been reduced. Also, with a general increase in the nutritional level of the community and an increase in personal vitality; the risk of contracting the germ is much less. This is one of the major advantages of living in today’s modern world.
Nevertheless, these sophisticated conditions are not present in many developing countries, and this is why the disease is still rife in so many impoverished lands even today.
Very small numbers of germs may establish infection in a person exposed to the germs. The tubercle bacillus has a predilection for the lung tissue, although tuberculosis may occur in virtually any organ of the body. In the lung, in the primary infection, it is the upper part that is usually affected first.