It can be quite lethal depending on the strain and various health factors. It is a serious illness, but can be treatable (once again, depending on the strain of tuberculosis involved and other...
Most diseases can be both non-lethal or lethal, depending on factors such as: the patient's prior health status the patient's pre-existing conditions such as COPD the patient's overall condition such...
There is NO "no effect dose" dose or "lethal effect" dose for viruses, bacteria, and other microorganisms, because they make you ill by multiplying at first in number ('growth')
If left untreated it can definitely be deadly but in most cases it takes years before the virus even becomes active. Even in it's worst stages it can be treated and cured.