TB is airborne and caused by mycobacterium africanum, mycobacterium bovis, and mycobacterium tuberculosis often collectively termed M. tuberculosis complex. TB can affect any part of the body, when it affects several sites it is referred to as military tuberculosis. If it affects organs excluding the lungs it is referred to as extra-pulmonary TB. Generally though, most TB is pulmonary, and it is pulmonary TB that is transmitted, although close contact is required for long periods. It is transmitted by infected droplets in coughs, sneezes, breathing, or even talking. TB can be transmitted from animals to humans; cattle are particularly prone (in this case it can be transmitted also through contaminated meat or milk). In this case it is possible to spread extra-pulmonary TB.
Pulmonary TB occurs when the bacillus is inhaled into the alveoli, this is the primary focus of the infection, and will develop into a granuloma. During the primary stage of the infection, the bacteria may be transported to the lymph nodes. Generally in healthy people the infection will be killed off with no treatment, however, in some patients, particularly those who are immunocompromised, the bacteria will not be completely eradicated, and may lie in a dormant state, which may later become infectious. While dormant, TB cannot be spread, and the patient will be asymptomatic. If the disease is active, and the lungs are involved, this is then infectious. The active disease is more prevalent in those who are immunocompromised due to HIV infection, the ageing process, or immunosuppressant therapy. Those with diabetes or who are pregnany or have co-existing diseases are also likely to be infected.
Symptoms can differ with the site of the TB; pain from bone TB, haematuria and dysuria with renal TB, and with TB meningitis headaches, nausea, vomiting, and lymph node swelling. It is always important to consider whether pulmonary TB is also present (due to its contagion ability) when any of these symptoms occur. Pulmonary TB may present with weight loss, night sweats and/or fever, cough, haemoptysis, shortness of breath, malaise or lethargy.
Treatment of TB is comprehensive and therefore requires commitment from the patient. Several drugs may be required, and the medication schedule may last for at least six months. Patients should be made aware that drugs may have serious side effects, but that continuation of the treatment schedule is vital.