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Many people
think tuberculosis (TB) is a disease of the
past. But,
Tuberculosis is still a leading
killer of young adults worldwide. Some 2
billion people – one-third of the world's
population – are infected with the
tuberculosis bacterium,
M.
tuberculosis.
Tuberculosis is a chronic bacterial
infection. It is spread through the air and
usually infects the lungs, although other
organs are sometimes involved.
Most persons
that are infected with
M.
tuberculosis
harbor the bacterium without symptoms but
many develop active tuberculosis disease.
Each year, 8 million people worldwide
develop active tuberculosis and 3 million
die.
What caused tuberculosis to return?
Cases of
TB dropped rapidly in the 1940s
and 1950s when the first effective
antibiotic therapies for tuberculosis
were introduced.
In 1985,
however, the decline ended and the number of
active tuberculosis cases in the United
States began to rise again. Several forces,
often interrelated, were behind
tuberculosis's resurgence:
- The
HIV/AIDS epidemic. People with HIV are
particularly vulnerable to turn infection
with M.
tuberculosis into
active
tuberculosis and are also more sensitive
to developing active tuberculosis when
they are first infected with the
tuberculosis germ.
- Increased
numbers of foreign-born nationals from
countries where many cases of tuberculosis
occur, such as Africa, Asia, and Latin
America. Tuberculosis cases among those
persons now living in the US account for
nearly half of the national total.
- Increased
poverty, injection drug use, and
homelessness. Tuberculosis transmission is
rampant in crowded shelters and prisons
where people weakened by poor nutrition,
drug addiction, and alcoholism are exposed
to M.
tuberculosis.
- Failure of
patients to take their prescribed
antibiotics against tuberculosis as
directed.
- Increased
numbers of residents in long-term care
facilities such as nursing homes. Many
develop active tuberculosis from
infections with
M.
tuberculosis
that occurred much earlier in life because
their general health has declined. Other
elderly people, especially those with weak
immune systems, become newly infected with
M.
tuberculosis and can rapidly
develop active tuberculosis.
How do people catch tuberculosis?
Tuberculosis
is primarily an airborne disease. The
disease is spread from person to person in
tiny microscopic droplets when a
tuberculosis sufferer coughs, sneezes,
speaks, sings, or laughs.
Only people with
active disease are contagious.
It usually
takes lengthy contact with someone with
active tuberculosis before a person can
become infected. On average, people have a
50 percent chance of becoming infected with
M.
tuberculosis if they spend eight
hours a day for six months or 24 hours a day
for two months working or living with
someone with active tuberculosis. However,
people with tuberculosis who have been
treated with appropriate drugs for at least
two weeks are no longer contagious and do
not spread the germ to others.
Adequate
ventilation is the most important measure to
prevent the transmission of tuberculosis.
Is tuberculosis a problem in the United
States?
In the United
States, tuberculosis has re-emerged as a
serious public health problem. In 2001,
based on provisional data reported to the
U.S. Centers for Disease Control and
Prevention, the number of cases has
decreased for the ninth straight year to
15,991 cases of active tuberculosis
(infection with full-blown disease
symptoms). This all-time low is due largely
to improved public health control measures.
In addition to those with active
tuberculosis, however,
an estimated 10 to 15
million people in the United States are
infected with
M.
tuberculosis
without displaying symptoms (latent
tuberculosis) and about one in ten of these
individuals will develop
active tuberculosis
at some time in their lives.
Minorities
are affected disproportionately by
tuberculosis: 54 percent of
active
tuberculosis cases in 1999 were among
African-American and Hispanic people, with
an additional 20 percent found in Asians.
Tuberculosis Symptoms
Between two
to eight weeks after being infected with
M.
tuberculosis, a person's
immune
system responds to the tuberculosis germ by
walling off infected cells. From then on the
body maintains a standoff with the
infection, sometimes for years. Most people
undergo complete healing of their initial
infection, and the bacteria eventually die
off. A positive tuberculosis skin test, and
old scars on a chest x-ray, may provide the
only evidence of the infection.
If, however,
the body's resistance is low because of
aging, infections such as
HIV, malnutrition,
or other reasons, the bacteria may break out
of hiding and cause active tuberculosis.
What is "active" tuberculosis disease?
One in ten
people that are infected with
M.
tuberculosis may develop active
tuberculosis at some time in their lives.
The risk of developing active disease is
greatest in the first year after infection,
but active disease often does not occur
until many years later.
Early
symptoms of active tuberculosis can include
weight loss, fever, night sweats, and loss
of appetite, or they may be vague and go
unnoticed by the affected individual. One in
three patients with tuberculosis will die
within weeks to months if the disease is not
treated. For the rest, their disease either
goes into remission (halts) or becomes
chronic and more debilitating with cough,
chest pain, and bloody sputum.
Symptoms of
tuberculosis involving areas other than the
lungs vary, depending upon the organ
affected.
How is tuberculosis diagnosed?
Doctors can
identify most people infected with
M.
tuberculosis with a skin test. They
will inject a substance under the skin of
the forearm. If a red welt forms around the
injection site within 72 hours, the person
may have been tuberculosis infected. This doesn't
necessarily mean he or she has active
tuberculosis disease. Most people with previous exposure
to M.
tuberculosis will test
positive on the tuberculin test, as will
some people exposed to bacteria that are
related to the tuberculosis germ.
If a person has
an obvious reaction to the skin test, other
methods can help to show if the individual
has active tuberculosis. In making a
diagnosis, doctors rely on symptoms and
other physical signs, a person's history of
exposure to tuberculosis, and x-rays that
may show evidence of
M.
tuberculosis
infection. |
