Unlike asthma or COPD, tuberculosis has a known cause. It results from infection by a bacterium known as Mycobacterium tuberculosis. While secondary infections are more likely when a person has COPD (as a result of the tendency to retain excess mucus), the bacterial infection itself is the prime cause of TB.

The symptoms of TB are also very different from those other, now more common lung diseases. Coughing is seen in both, but in TB this is accompanied by coughing up blood, severe chest pain, fever, and night sweats. While COPD creates shortness of breath and sometimes fatigue from difficulty of breathing, tuberculosis is often fatal if left untreated.

The disease most commonly attacks the upper lobe of the lungs, but other organs can be affected. Any spread inside the body is often accelerated by the germ's migration through the lymph system, since there are several lymph nodes near the lungs. In some cases, the body's own immune system is adequate to kill the germ and clear the disease.

Fortunately, there are simple tests that will detect the presence of the germ.

One common one is, happily, much less well-known now than in generations past thanks to many fewer cases. During a skin test a doctor injects a small amount of special fluid into the lower arm. The arm is checked 48-72 hours later for a characteristic swollen and reddened appearance at the site of the injection. It results from the interaction of the germ with the fluid, which contains deactivated TB proteins.

But the test can only detect the presence of the TB-causing organism, not the disease itself. Since it is possible for the germ to be dormant, a condition called Latent Tuberculosis, it is possible to house the bacteria but not be ill.

Follow up tests, such as an x-ray exam and sputum analysis, are performed when the skin test is positive. X-rays may show scarring (fibrosis), as the body wraps the germ in scar tissue, or calcification (hardening) in the lungs. Sputum analysis can directly detect the presence of the bacterium by using a special stain or dye.

When the germ is still latent it may reside in the lungs but will generally be absent from sputum. Though unlikely, it is possible to house the organism and never develop the full-blown disease. However, the longer the germ is retained without generating symptoms, the lower the odds of ever developing active TB.

Since it is an infectious disease, tuberculosis can be spread by proximity to an infected person. The germ can be injected into the air during a cough or sneeze. Indeed, millions caught it and died just that way around the turn of the 20th century. Fortunately, there are now vaccines that can help prevent the disease, and therefore curtail any spread. The most common vaccine is called BCG (Bacille Calmette-GuÈrin), after its developer.

However, in many countries around the world vaccination is not routine. Therefore, several treatments are still in widespread use for both Latent TB and its active form.

Latent TB is treated with antibiotics used to kill the infecting organism. Since there are different strains of the bacteria, often more than one drug will be used simultaneously to combat the illness.

Sadly, there are forms - called MDR-TB (Multiple Drug Resistant TB) and XDR-TB (Extensively drug-resistant TB) - that do not respond to the standard drugs. In this case, physicians employ a specialized regimen of treatment. Luckily, only about 10% of cases fall into either of those categories.