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When the
World Health Organization announced in 1993 that
tuberculosis (TB) should be treated as a global
emergency, the international community’s response was
slow and uncoordinated.
Although
initial progress has since been made in controlling the
disease, the emergence of a deadly HIV-TB co-infection
epidemic and extensively drug-resistant (XDR) strains of
TB means that a more serious and aggressive strategy is
essential to fight the world’s second-biggest infectious
disease.
Practical action
What
needs to be done? More research is undoubtedly
necessary. Understanding the social factors deterring
people from seeking diagnosis or treatment, removing the
barriers to accessing care, and devising new strategies
to diagnose TB in children and HIV/AIDS patients are key
priorities.
When the
genome of the bacterium that causes TB has been
sequenced, researchers will be able to look for ways to
defeat it. Understanding immunity to the disease may
also help researchers who have so far been frustrated in
efforts to develop a new, long-lasting vaccine.
But
there are practical measures that can be implemented
using existing knowledge: integrating TB and HIV
efforts—especially in sub-Saharan Africa—and
strengthening health systems are just two examples.
Two-thirds of TB cases could be detected with existing
diagnostic methods if only these techniques were widely
and effectively implemented. These measures will need
tremendous national commitment as well as international
support and guidance.
Need for
information
Just as
important as these actions is the need for accurate
information. This means not only training health-care
workers to understand the growing challenges of TB, but
also educating the wider population to dispel any
lingering myths about TB and combat the stigma
associated with this disease. Raising awareness of the
increased risk of TB infection for people with HIV and
helping people know when they might be at risk of having
latent or ‘hidden’ TB, are also key.
This
spotlight offers the simple facts and figures about TB
but also delves into more complex issues—in particular,
the obstacles confronting mandatory quarantine of
patients with drug-resistant TB, the problem of
overlapping HIV and TB epidemics and the clinical
challenges for drug development.
The
facts show undeniably that tuberculosis (TB) is a major
problem for the world’s poor. Over two billion people
worldwide carry the bacterium that causes TB, with
approximately 15 million people suffering from an active
infection at any one time.
The
disease burden is highest in developing countries where
people are especially vulnerable to TB because of poor
underlying health, adverse living conditions and limited
access to treatment.
Although
the disease is often treatable, for many people in these
nations it is fatal. TB kills 1.6 million people every
year; 4,400 people every day; one person every 20
seconds. 98 percent of all TB deaths occur in developing
countries.
The
economic implications of this devastation are huge:
fighting the disease drains $12 billion from the annual
incomes of the world’s poorest communities. The loss of
productivity attributable to TB is estimated to be 4
percent to 7 percent of gross domestic product.
Figure 1
shows the 10 countries with the highest numbers of TB
victims—including the Philippines—all are in the
developing world.
But it
is important to put overall numbers into context,
relative to a country’s population size. Figure 2 shows
the countries that have the highest prevalence of TB
sufferers per 100,000 of the population—a different
picture from Figure 1. Almost all of these countries are
in Africa, where resources for TB treatment and control
are limited.
About the disease
TB is an
infectious disease caused by the Mycobacterium
tuberculosis bacterium, which most commonly affects the
lungs. There are two forms of TB: active, where a
patient has symptoms and an abnormal chest x-ray; and
latent, where a person has no symptoms and their chest
x-ray is normal, but a skin test gives a positive result
for TB.
The
symptoms of active TB of the lungs include
coughing—sometimes with sputum or blood—chest pains,
weakness, weight loss, fever and night sweats. It is
spread through the air when infected people cough,
sneeze or speak.
Despite
its prevalence, many people are unaware of the
complexities of TB—for example, that it can lie dormant
in seemingly healthy people. Accurate information is key
to tackling any major disease epidemic and unless people
know what the symptoms of TB are, they are unlikely to
get treatment before reaching the infectious stage of
active disease.
Strategies for controlling TB increasingly include
education aimed at informing people of the key symptoms
of TB and dispelling the common myths that surround this
disease
TB and
HIV/AIDS
TB is
the leading infectious killer of people with HIV/AIDS,
and a particular problem in sub-Saharan Africa, where a
third of people with HIV are also infected with TB. In
most of these countries, over half of patients
presenting with TB are coinfected with HIV (see Table
1).
Because
of their weakened immune systems, HIV/AIDS patients are
up to 20 times more likely to develop TB than people
without HIV. TB is also more fatal in HIV/AIDS patients,
with up to half of all deaths of HIV/AIDS patients due
to TB. A person with both diseases can be four times
more likely to die during TB treatment than someone with
TB alone.
Yet,
effective treatment of HIV/AIDS patients infected with
TB is still possible, principally through the addition
of an antibiotic, cotrimoxazole, which can reduce the
death rate during TB treatment by 40 percent.
Still,
stigma related to both diseases can mean that patients
infected with one disease are reluctant to voluntarily
be tested for the other. The lack of integration across
national HIV/AIDS and TB control programs also means
that routine screening of TB patients for HIV, and vice
versa, is not in place for many developing countries
TB
treatment
Current
treatment consists of six- to nine-month courses using a
combination of two or more of the four first-line drugs:
isoniazid, ethambutol, pyrazinamide and rifampin. These
regimens work for active, drug-susceptible TB—as long as
the course is completed.
Not
completing the course can lead to relapse, continued
transmission and the development of drug resistance—a
growing concern in the fight against TB.
One
strategy that has been adopted by the World Health
Organization (WHO) to help ensure that patients complete
TB treatment is directly observed therapy (DOT), where a
health worker watches the patient swallow each dose of
TB medication.
One of
the Millennium Development Goals set for 2015 is to
reduce the prevalence of and deaths due to TB by 50
percent of 1990 figures. DOT can lead to more successful
treatments of infectious TB, which can, in turn, help
prevent the spread of the disease.
Drug resistance
About
450,000 new cases of multidrug-resistant TB (MDR-TB)
occur every year, with the highest prevalence in China,
India and the countries of the former Soviet Union.
These
patients cannot be treated with first-line drugs and
often require extensive chemotherapy for up to two
years. In 1999, the WHO launched the DOTS-Plus program
to manage MDR-TB with second-line drugs in
resource-limited settings. This includes integrating
drug resistance surveillance into TB control strategies
and scaling up MDR-TB treatment.
The
major barrier to treatment of MDR-TB in developing
countries is the high cost of second-line drugs, which
are between 300 and 3,000 times more expensive than
first-line drugs. Other barriers include the limited
number of laboratories equipped for drug-susceptibility
testing and the fear of developing extensively
drug-resistant TB (XDR-TB)—where the disease is
resistant to second-line drugs as well as first-line
ones.
Cases
have been confirmed in
KwaZulu-Natal,
South Africa—where 52 of 53 patients diagnosed with XDR-TB
died within 25 days of sputum collection—and worldwide.
The
resistance to second-line drugs makes XDR-TB extremely
difficult to treat. But new drugs are in the pipeline.
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