Overview
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.
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.
What caused tuberculosis to return?
Cases of tuberculosis 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.
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" 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 infected.
This doesn't necessarily mean he or she has active 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.
The doctor also will take sputum and other samples, to see if the
tuberculosis bacteria will grow in the lab. If bacteria are growing, this
positive culture confirms the diagnosis of tuberculosis. Because M.
tuberculosis grows very slowly, it can take four weeks to
confirm the diagnosis. An additional two to three weeks usually are
needed to determine which antibiotics the bacteria are susceptible
to.
Can tuberculosis be cured?
With appropriate antibiotic treatment, tuberculosis can be cured in more
than nine out of ten patients.
Successful tuberculosis treatment depends on close cooperation between
the patient and doctor and other health care workers. Tuberculosis treatment
usually combines several different antibiotic drugs which are given
for at least six months, sometimes for as long as 12 months.
Patients must take their medicine on time every day for the 6 to
12 months. Some tuberculosis patients stop taking their prescribed medicines
because they may feel better after only a couple of weeks of
treatment. Another reason they may stop taking their medicine is
because tuberculosis drugs can have unpleasant side effects.
Why is it so important to finish all of the tuberculosis
medicine?
If patients don't take all their medicine the way their doctor
tells them, they can become sick again and spread tuberculosis to their
friends and family. Additionally, when patients do not take all the
drugs the doctor has prescribed or skip times when they are supposed
to take them, the tuberculosis bacteria learn to outwit the tuberculosis antibiotics,
and soon those medications no longer work against the disease. If
this happens, the person now has resistant tuberculosis infection. Some
patients have disease that is resistant to two or more drugs. This
is called multidrug-resistant tuberculosis or MDR-tuberculosis because the tuberculosis germ,
M. tuberculosis resists eradication with more than drug.
This form of tuberculosis is much more difficult to cure.
Tuberculosis Treatments
Treatment for MDR-tuberculosis often requires the use of special tuberculosis drugs,
all of which can produce serious side effects. To cure MDR-tuberculosis,
patients may have to take several antibiotics, at least three to
which the bacteria still respond, every day for up to two years.
However, even with this treatment, between four and six out of ten
patients with MDR-tuberculosis will die, which is the same as for patients
with normal tuberculosis who do not receive treatment.
How is tuberculosis prevented?
tuberculosis is largely a preventable disease. In the United States,
doctors try to identify persons infected with M.
tuberculosis as early as possible, before they have developed
active tuberculosis. They will give a drug called isoniazid (INH) to prevent
the active disease. This drug is given every day for 6 to 12 months.
INH can cause hepatitis in a small percentage of patients,
especially those older than 35 years. A nurse may watch the patients
take their medicine to make sure all pills are taken.
Hospitals and clinics can take precautions to prevent the spread
of tuberculosis. Precautions include using ultraviolet light to sterilize the
air, special filters, and special respirators and masks. Until they
can no longer spread the tuberculosis germs, tuberculosis patients in hospitals should
be isolated in special rooms with controlled ventilation and
airflow.
Is there a vaccine for tuberculosis?
In those parts of the world where the disease is common, the
World Health Organization (WHO) recommends that infants receive a
vaccine called BCG made from a live weakened bacterium related to
M. tuberculosis. BCG vaccine prevents M.
tuberculosis from spreading within the body, thus preventing tuberculosis
from developing.
However, the vaccine has its drawbacks. It does not protect
adults very well against tuberculosis. In addition, BCG interferes with the tuberculosis
skin test, showing a positive skin test reaction in people who have
received BCG vaccine. In countries where BCG vaccine is used, the
ability of the skin test to identify persons that are infected with
M. tuberculosis is limited. Because of these limitations,
more effective vaccines are needed and BCG is not recommended for
general use in the United States.
How is M. tuberculosis infection different in
people with HIV infection?
The World Health Organization (WHO) estimates that 10 million
people worldwide are infected with the M. tuberculosis
bacterium and HIV virus at the same time. The primary cause of death
in these patients is from tuberculosis, not AIDS. In the United States, it is
estimated that about 2 out of ten persons who have tuberculosis are also
infected with HIV.
One of the first indications that a person is infected with HIV
may be that he or she suddenly develops tuberculosis. This form of tuberculosis often
occurs in areas outside the lungs, particularly when the patient is
in the later stages of AIDS.
In the United States, it is much more likely for persons infected
with M. tuberculosis and HIV to develop active tuberculosis than it
is for someone that is only infected with M. tuberculosis.
However, tuberculosis disease can be prevented and cured, even in people with
HIV infection.
People with MDR-tuberculosis that are also infected with HIV appear to have
a more rapid and deadly disease course than do those patients with
MDR-tuberculosis who are otherwise healthy. If no medicines are available for
these patients as many as eight out of ten may die, often within
months of diagnosis.
Diagnosing tuberculosis in HIV-infected people is often difficult. HIV
infected patients frequently have disease symptoms similar to those
of tuberculosis, and may not react to the standard tuberculosis skin test because their
immune system does not work properly. X-rays, sputum tests, and
physical exams may also fail to provide evidence of infection with
M. tuberculosis in HIV-infected individuals.
How is research helping the fight against
tuberculosis?
tuberculosis research
supports not only studies to better understand how M.
tuberculosis infects and causes disease in humans but also how
the human immune system responds to it. This research will help to
develop new tools to diagnose tuberculosis, find better vaccines, and new
medicines against tuberculosis. Below are some important advances that have
been made in tuberculosis research:
Diagnosis: Potential new tests to speed the
diagnosis of tuberculosis from four weeks to two days; differences found in
the DNA of M. tuberculosis and the bacterium used in the
BCG vaccine may lead to a test to tell the difference between people
who really have tuberculosis and those who only react to previous BCG
vaccination.
Treatment: Discovery of the molecules
responsible for drug resistance, knowledge that will help doctors
quickly select the best treatments for their patients; a new drug
under study can be taken less often to help patients comply with
their treatment regimen.
Vaccines: More than 90 vaccine candidates have
been developed and tested in animals.
Keeping on Top of Your Condition
Keeping in tune with your disease or condition not only makes treatment less intimidating but also increases its chance of success, and has been shown to lower a patients risk of complications. As well, as an informed patient, you are better able to discuss your condition and treatment options with your physician.
A new service available to patients provides a convenient means of staying informed, and ensures that the information is both reliable and accurate. If you wish to find out more about HealthNewsflash's innovative service, take the tour.
| 
