TB which is also known as tuberculosis, is an infectious disease caused by the bacillus Mycobacterium tuberculosis and characterized by the formation of nodular lesions (tubercles) in the tissues.
- Bacillus inhaled into the lungs:
In pulmonary tuberculosis – formerly known as consumption and pthisis (wasting – the bacillus is inhaled into the lungs where it sets up a primary tubercle and spreads to the nearest lymph nodes (the primary complex). Natural immune defences may heal it at this stage. Alternatively the disease may smoulder for months or years and fluctuate with the patient’s resistance. Many people become infected but show no symptoms. Others develop a chronic infection and can transmit the bacillus by coughing and sneezing.
- Bacillus entering by mouth e.g. in infected cow’s milk:
Set up a primary complex in the abdominal lymph nodes, leading to peritonitis, and sometimes spread to other organs, joints, and bones.
Symptoms of active tuberculosis include fever, night sweats, weight loss, and the spitting of blood.
In some cases the bacilli spread from the lungs to the bloodstream, setting up millions of tiny tubercles throughout the body (military tuberculosis), or migrate to the meninges to cause tuberculous meningitis.
Tuberculosis is curable by various combinations of antibiotics. Preventative measures used in the UK have included the detection of cases by X-ray screening of vunerable populations and inoculation with BCG vaccine.
See also a list of diseases and disorders of the respiratory system (info all on one page).