Digestive 
Blood
Cardiovascular
Dermatology
Genitourinary,
Hormones
Infections
Oncology and
Musculo-skeletal
Mental health and
Parasites
Respiratory
Senses
Various
About a third of the world's population may be infected with Mycobacterium tuberculosis, which causes tuberculosis bacillus.
The transmission of tuberculosis bacilli occurs almost exclusively via droplets that are expelled with the phlegm of those affected by pulmonary tuberculosis. These droplets can remain infective in the air for quite some time and can be inhaled by others.
Infection is more likely to occur when someone lives with or has prolonged contact with the patient who is expelling bacilli and is in a poorly ventilated room.
Not all infected people get sick. Pulmonary tuberculosis is the most common.
