Tuberculosis – An Old Illness that Never Went Away
Recent events regarding the discovery of a couple of cases
of Tuberculosis (TB) at a local High School serve to remind us that some
diseases don’t ever really go away. Many
of us had nearly forgotten about TB. At one time, most children got TB tests a number of times
during their check up years. Now, a
TB test is no longer required for
most children before Kindergarten or going into college.
The old Tine Test that poked into our arms isn’t even used any more. It
turns out that testing people who are at a low risk for TB, that is most
children in the US, wasn’t very effective.
TB is an infection, usually in the lungs, that is caused by
bacteria called Mycobacterium tuberculosis.
A healthy person, when exposed to this bacterium, may have only a mild
illness or no symptoms. However, as
the person fights off the germ, it may simply be walled off, or locked up in a
cyst in the lung, sometimes even too small to see on an x-ray.
At a later date, under stress of an illness or surgery or decreased
immune function, the TB germ may “wake up” and cause a severe illness and
allow spread to others through coughing or exposure to lung fluids.
TB is so contagious if not treated, in times past, people infected were
sent to special hospitals and forced to live there so as to not spread the
disease to others through coughing, etc. With
the advent of medicines to treat TB, we no longer need to isolate people once
they have begun treatment. As an
aside, there are areas in the world, such as prisons in the former Soviet Union,
where resistant strains of tuberculosis have emerged.
The way we look at TB these days is to worry less about
populations at low risk and more about people who we think are at a higher risk
for really having the disease. These
high risk people would include anyone who has had recent exposure (e.g. living
with or working closely with) to someone who had active TB; people who recently
moved from an area that is known to have a high TB rate; persons from homeless
shelters and people who work in shelters, hospitals, prisons and nursing homes.
These are the people we need to be especially careful about testing.
The way to test for TB is with a test called a PPD – or
also called a Mantoux (mantoo) test. With
this, a very tiny needle and a serum is used to raise up a little bump under the
skin, usually on the forearm. If a
person has had exposure to the TB germ, the spot will swell up over the next
48-72 hours. Depending on how much
risk, the test is judged positive or negative based on how big the swelling is
at that time. If a person were in
the lowest risk, the test would be considered negative even if the swelling were
as big as 15mm (a little over ½ “). If, however, someone were in the group
considered higher risk, such as a recent immigrant, the test would be called
positive if it were over 5mm (< ¼ ”).
Once the test is called positive, the person must have a chest x-ray to
look for any signs of active TB, and then begin a nine month course of daily
medication. This medication, called
Isoniazid (INH) has some side effects such as nausea and lab work needs to be
checked monthly to be sure it is not hurting the liver. While this may not seem
so pleasant, it is the only way we have to decrease the chance of the latent or
sleeping TB infection from becoming active and possibly spreading to others.
Once a person is taking medication to fight the germ, they are felt to be
not infectious and may return to their usual daily activities.
For more information about Tuberculosis – check out http://www.aafp.org/afp/20000501/2681ph.html
Joseph Moore, PA-C
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