Tuberculosis


Tuberculosis (TB) is an infectious disease caused by a germ (bacterium) called
Mycobacterium tuberculosis. This germ primarily affects the lungs and may infect
anyone at any age.

In the United States, the number of TB cases steadily decreased until 1986 when
an increase was noted; TB has continued to rise since. Today, ten million
individuals are infected in the U.S., as evidenced by positive skin tests, with
approximately 26,000 new cases of active disease each year. The increase in TB
cases is related to HIV/AIDS, homelessness, drug abuse and immigration of
persons with active infections.

How is TB Contracted?

TB is a contagious or infectious disease that is spread from person-to- person.
A person is usually infected by inhaling the germs which have been sprayed into
the air by someone with the active disease who coughs.

However, inhaling the germ does not usually mean you will develop active disease.
A person\'s natural body defenses are usually able to control the infection so
that it does not cause disease. In this case, the person would be infected, but
not have active disease. Only about 10% of those infected will actually develop
TB in their lifetimes.

Active disease can occur in an infected person when the body\'s resistance is low
or if there is a large or prolonged exposure to the germs that overcome the
body\'s natural defenses. The body\'s response to active TB infection produces
inflammation which can eventually damage the lungs. The amount of damage may be
quite extensive, yet the symptoms may be minimal. The usual symptoms of disease
due to TB are:

-Fever -Night sweats -Cough -Loss of appetite -Weight Loss -Blood in the sputum
(phlegm) -Loss of energy

Diagnosing TB

To diagnose TB, your clinician will gather five important pieces of information:


-Symptoms -History of possible exposure and onset of symptoms -Tuberculin skin
test or PPD -Chest X-ray •Sputum test

Tuberculin Skin Test

The tuberculin skin test (or PPD) is performed with an extract of killed
tuberculosis germs that is injected into the skin. If a person has been infected
with tuberculosis, a lump will form at the site of the injection--this is a
positive test. This generally means that TB germs have infected the body. It
does not usually mean the person has active disease. People with positive skin
tests but without active disease cannot transmit the infection to others.

Chest X-Ray

If a person has been infected with TB, but active disease has not developed, the
chest X-ray usually will be normal. Most people with a positive PPD have normal
chest X-rays and continue to be healthy. For such persons, preventive drug
therapy may be recommended.

However, if the germ has attacked and caused inflammation in the lungs, an
abnormal shadow is usually visible on the chest X-rays. For these persons,
aggressive diagnostic studies (sputum tests) and treatment usually are
appropriate.

Sputum Test

Samples of sputum coughed up from the lungs can be tested to see if TB germs are
present. The sputum is examined under a microscope (a "sputum smear") to look
for evidence of the presence of TB organisms. The organisms are then grown in
the laboratory to identify them as TB germs and to determine what medications
are effective in treating them. These studies are referred to as culture and
susceptibility testing. State health department laboratories and reference
laboratories can perform such testing.

Treatment of TB

Individuals with a positive tuberculin skin test may or may not receive
preventive drug therapy depending on the exposure history, the timing of the
skin test conversion (when the test changes from negative to positive) and other
factors in the individual\'s medical history. When it is known that a person has
recently been in close contact with an individual with active tuberculosis and
has developed a positive tuberculin skin test, preventive treatment is advisable
due to a relatively high risk of developing active disease. Isoniazid (INH) may
be prescribed for six to nine months as preventive treatment and for twelve
months in persons who are HIV positive.

Since the advent of anti-tuberculosis drugs in the 1940s, the treatment of drug
susceptible tuberculosis has become highly effective if administered and taken
properly. Treatment no longer requires prolonged hospital stays. In many cases,
a patient with a new case of TB can be treated at home. Others will enter the
hospital to be placed on a medication program and to be isolated until the
disease is controlled. When the person is no longer infectious, he or she can
leave the hospital and continue on medication at home. Hospitalization in such
cases may be a few weeks to several months depending on the severity of the
disease and the