TB is spread from person to person through the air. When
people with lung TB cough, sneeze or spit, they propel the TB germs into
the air. A person needs to inhale only a few of these germs to become
infected. When a person develops active TB (disease),
the symptoms (cough,
fever, night sweats, weight loss etc.) may be mild for many months. This
can lead to delays in seeking care, and results in transmission of the
bacteria to others. People ill with TB can infect up to 10-15 other
people through close contact over the course of a year. Without proper
treatment up to two thirds of people ill with TB will die.
Common symptoms of active lung TB are cough with sputum and
blood at times, chest pains, weakness, weight loss, fever and night
sweats, Many countries still rely on a long-used method called sputum
smear microscopy to diagnose TB. Trained laboratory technicians look at
sputum samples under a microscope to see if TB bacteria are present.
With three such tests, diagnosis can be made within a day, but this test
does not detect numerous cases of less infectious forms of TB. Diagnosing MDR-TB (see Multidrug-resistant TB section below)
and HIV-associated TB can be more complex. A new two-hour test that has
proven highly effective in diagnosing TB and the presence of drug
resistance is now being rolled-out in many countries.
resistant to a single anti-TB drug have been documented in every country
The primary cause of MDR-TB is inappropriate treatment.
Inappropriate or incorrect use of anti-TB drugs, or use of poor quality
medicines, can all cause drug resistance.
In some cases more severe drug resistance can develop.
Extensively drug-resistant TB, XDR-TB, is a form of multi-drug resistant
tuberculosis that responds to even fewer available medicines, including
the most effective second-line anti-TB drugs.