"R.K." asked:

alt.support.tuberculosis

Most cases of TB occur among people living under conditions of
overcrowding, poor sanitation and inadequate nutrition.  The former
encourages spread and the latter makes it more difficult to fight the
infection.  In a healthy person a TB infection often goes dormant,
sometimes for decades, until age or other illnesses allow it to break
out again.

In the Third World, TB is common, and spreads rapidly, and in the
absence of medical care or other efforts (like isolation) to slow its
spread, has become epidemic.  Note also that people with AIDS readily
acquire TB and in some parts of sub-Sahara Africa, HIV infection is
as high as 40% of the population.  In developed countries, TB is
mainly a disease of the very poor, but of course, anyone can acquire
it if exposed.

In the US, 100 years ago, TB killed about one person in four, and
the rate was highest among the urban poor, who lived in the kind
of conditions common in today's Third World. Rural people and
the well-to-do also got it, but were less likely to die of it.