FAQS
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Definition
of the disease
Tuberculosis
kills 2 million people each year. The global epidemic
is growing and becoming more dangerous. The breakdown
in health services, the spread of HIV/AIDS and the emergence
of multidrug-resistant TB are contributing to the worsening
impact of this disease.
In
1993, the World Health Organization (WHO) took an unprecedented
step and declared tuberculosis a global emergency, so
great was the concern about the modern TB epidemic.
It
is estimated that between 2000 and 2020, nearly one
billion people will be newly infected, 200 million people
will get sick, and 35 million will die from TB - if
control is not further strengthened.
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Infection
and Transmission
TB
is a contagious disease. Like the common cold, it spreads
through the air. Only people who are sick with pulmonary
TB are infectious. When infectious people cough, sneeze,
talk or spit, they propel TB germs, known as bacilli,
into the air. A person needs only to inhale a small
number of these to be infected.
Left
untreated, each person with active TB will infect on
average between 10 and 15 people every year. But people
infected with TB will not necessarily get sick with
the disease. The immune system 'walls off' the TB bacilli
which, protected by a thick waxy coat, can lie dormant
for years. When someone's immune system is weakened,
the chances of getting sick are greater.
- Someone in the world is newly infected with TB
every second.
- Nearly one percent of the world's population is
newly infected with TB each year.
- Overall, one-third of the world's population is
currently infected with the TB bacillus.
- 5 - 10 percent of people who are infected with
TB become sick or infectious at some time during their
life.
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Global
and Regional Incidence
Each
year, more people are dying of TB. New outbreaks have
occurred in Eastern Europe, where TB deaths are increasing
after almost 40 years of steady decline. In terms of
numbers of cases, the biggest burden of TB is in south-east
Asia.
- TB kills about 2 million people each year.
- Around 8 million people become sick with TB each
year.
- Over 1.5 million TB cases per year occur in sub-Saharan
Africa. This number is rising rapidly as a result
of the HIV/AIDS epidemic.
- Nearly 3 million TB cases per year occur in south-east
Asia.
- Over a quarter of a million TB cases per year occur
in Eastern Europe.
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Factors
Contributing to the Rise in TB
HIV
is accelerating the spread of TB
HIV
and TB form a lethal combination, each speeding the
other's progress. HIV weakens the immune system. Someone
who is HIV-positive and infected with TB is many times
more likely to become sick with TB than someone infected
with TB who is HIV-negative. TB is a leading cause of
death among people who are HIV-positive. It accounts
for about 15% of AIDS deaths worldwide. In Africa, HIV
is the single most important factor determining the
increased incidence of TB in the last ten years.
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Poorly
managed TB programmes are threatening to make TB incurable
Until
50 years ago, there were no drugs to cure TB. Now, strains
that are resistant to a single drug have been documented
in every country surveyed and, what is more, strains
of TB resistant to all major anti-TB drugs have emerged.
Drug-resistant TB is caused by inconsistent or partial
treatment, when patients do not take all their drugs
regularly for the required period because they start
to feel better, doctors and health workers prescribe
the wrong treatment regimens or the drug supply is unreliable.
A particularly dangerous form of drug-resistant TB is
multidrug-resistant TB (MDR-TB), which is defined as
the disease due to TB bacilli resistant to at least
isoniazid and rifampicin---the two most powerful anti-TB
drugs. MDR-TB is rising at alarming rates in some countries,
especially in the former Soviet Union, and threatens
global TB control efforts.
From
a public health perspective, poorly supervised or incomplete
treatment of TB is worse than no treatment at all. When
people fail to complete standard treatment regimens,
or are given the wrong treatment regimen, they may remain
infectious. The bacilli in their lungs may develop resistance
to anti-TB drugs. People they infect will have the same
drug-resistant strain. While drug-resistant TB is treatable,
it requires extensive chemotherapy (up to two years
of treatment) that is often prohibitively expensive
(often more than 100 times more expensive than treatment
of drug-susceptible TB), and is also more toxic to patients.
WHO
and its international
partners are have formed the DOTS-Plus Working Group,
which is attempting to determine the best possible strategy
to manage MDR-TB. One of the goals of DOTS-Plus is to
increase access to expensive second-line anti-TB drugs
for WHO-approved TB control programmes in low and middle
income countries.
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Movement
of people is helping the spread of TB
Global
trade and the number of people travelling in aeroplanes
have increased dramatically over the last forty years.
In many industrialized countries, at least one-half
of TB cases are among foreign-born people. In the US,
nearly 40% of TB cases are among foreign-born people.
The
number of refugees and displaced people in the world
is also increasing. Untreated TB spreads quickly in
crowded refugee camps and shelters. It is difficult
to treat mobile populations, as treatment takes at least
six months. As many as 50 percent of the world's refugees
may be infected with TB. As they move, they may spread
TB.
Other
displaced people such as homeless people in industrialized
countries are at risk. In 1995, approximately 30 percent
of San Francisco's homeless population and 25 percent
of London's homeless were reported to be infected with
TB. These figures compare to overall prevalences of
7 percent in the United States and 13 percent in the
United Kingdom. The prevalence of infection in prisons
can be even higher.
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Effective
TB Control
The
WHO-recommended treatment strategy for detection and
cure of TB is DOTS. DOTS combines five elements: political
commitment, microscopy services, drug supplies, surveillance
and monitoring systems and use of highly efficacious
regimes with direct observation of treatment.
Once
patients with infectious TB (bacilli visible in a sputum
smear) have been identified using microscopy services,
health and community workers and trained volunteers
observe and record patients swallowing the full course
of the correct dosage of anti-TB medicines (treatment
lasts six to eight months). The most common anti-TB
drugs are isoniazid, rifampicin, pyrazinamide, streptomycin
and ethambutol.
Sputum
smear testing is repeated after two months, to check
progress, and again at the end of treatment. A recording
and reporting system documents patients' progress throughout,
and the final outcome of treatment.
- DOTS produces cure rates of up to 95 percent even
in the poorest countries.
- DOTS prevents new infections by curing infectious
patients.
- DOTS prevents the development of MDR-TB by ensuring
the full course of treatment is followed.
- A six-month supply of drugs for DOTS costs US $11
per patient in some parts of the world. The World
Bank has ranked the DOTS strategy as one of the "most
cost-effective of all health interventions."
Since
DOTS was introduced on a global scale, millions of infectious
patients have received effective DOTS treatment. In
half of China, cure rates among new cases are 96 percent.
In Peru, widespread use of DOTS for more than five years
has led to the successful treatment of 91 percent of
cases.
By
the end of 1998, all 22 of the high burden countries
which bear 80% of the estimated incident cases had adopted
DOTS. 43 percent of the global population had access to DOTS, double the
fraction reported in 1995.
In the same year, 21 percent of estimated TB patients
received treatment under DOTS, also double the fraction
reported in 1995.
WHO
targets are to detect 70 percent of new infectious TB
cases and to cure 85 percent of those detected. Six
countries had achieved these targets in 1998. Governments,
non-governmental organizations and civil society must
continue to act to improve TB control if we are to reach
these targets worldwide.
Fact Sheet N°104
Revised April 2000
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