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Context - Tuberculosis (TB) is an infectious disease that affects a growing number of people around the world. Usually, it can be treated with antibiotics but some forms of the disease have emerged that do not respond to different types of drugs, making it very difficult to treat, especially in people already infected with HIV.
What are the trends in drug-resistant tuberculosis around the world and what must be done to control it?
1. What is tuberculosis and why is it a concern?
TB can be treated with antibiotics.
Source: TB Global drug
Tuberculosis (TB) is an
infectious disease caused by a
bacterium (most commonly
Mycobacterium tuberculosis) that mainly affects the
Many people who are infected
with the tuberculosis
bacterium will never become ill
because the infection is kept
under control by their
immune system and the
bacteria remain dormant. However,
if the infection becomes active, the person will become ill and have
symptoms such as coughing, weight loss, fever and chest pains. People
with a weakened immune system,
particularly those who are also infected with
HIV, have a greater chance of
becoming sick with TB.
When people with active
tuberculosis in their lungs cough,
sneeze, talk or spit, they propel TB germs into the air, which can
contaminate other people who inhale
Globally, the proportion of people who become ill with
tuberculosis each year is stable or
decreasing. However, because of
population growth, the absolute
number of new TB cases is rising.
Usually, tuberculosis can be
treated with antibiotics. However,
some forms of the disease have emerged that do not respond to these
“first-line drugs”. They are known
or MDR-TB, and can only be cured
with a handful of “second-line” drugs which are more expensive and have
more adverse effects.
Extensively drug-resistant tuberculosis,
or XDR-TB, refers to even more
dangerous forms of the disease that are resistant to both first- and
second-line drugs and are more
difficult to treat.
2. What is the Global Project on Anti-tuberculosis Drug Resistance Surveillance?
A network of supra-national laboratories supports the national laboratory
Source: Pierre Virot
Global Project on Anti-tuberculosis Drug Resistance Surveillance
was launched in 1994 by the World Health Organization
and other partners to respond to the emerging threat of drug-resistant
tuberculosis. The aim of the project is to evaluate drug-resistant
tuberculosis, to monitor its progress across the world, and to develop
plans to prevent and tackle it.
A network of 26
supra-national reference laboratories
supports countries by providing them with
drug resistance testing, by giving
them technical help, by checking the quality of the tests s performed by
the national laboratories and by collecting reliable data. The main
priorities for the network are to expand in order to meet the demand for
reference laboratories and to obtain regular funding.
3. What are current trends in drug-resistant tuberculosis?
TB Patients in a prison in Tbilsi, Georgia.
Source: Agnes Montanari
Worldwide, between 1 and 1.5 million people are living with
(MDR-TB). In 2006, there were nearly
half a million new cases in the world.
is present in nearly every country in the world but the proportion of
MDR-TB among all cases of
tuberculosis varies widely from one
region to another. For instance, it is lowest in Western and Central
Europe, and highest in Eastern Europe.
At present it is not possible to estimate global trends of
because information from high burden countries is lacking. The available
data suggest that different trends exist. For example,
MDR-TB is decreasing rapidly in
countries such as China and the United States, levelling off in others
such as Thailand and Viet Nam, and increasing very rapidly in parts of
the former Soviet Union.
It is very difficult to estimate the extent of the problem of
extensively drug-resistant tuberculosis
(XDR-TB) across the world because
few reliable data are available, particularly from the countries with
the highest burden of tuberculosis. Still, the problem is widespread,
with 45 countries having reported at least one case.
It is a particularly serious problem in countries of the former Soviet
Union, where it makes up a very high proportion of the region’s huge
number of cases of
4. Why do HIV and tuberculosis form a lethal combination?
HIV-TB patient in Thailand.
Source: Thiery Falise
There is a clear association between
infected with dormant tuberculosis
bacteria can quickly become sick
with tuberculosis when their immune systems are weakened by HIV.
Tuberculosis can be very difficult to detect in people who are
HIV-positive, which can cause delays in diagnosis. This, together with
the difficulty of treating both diseases at the same time, has led to
high death rates in people living with TB and HIV.
There are two main reasons why
HIV and drug-resistant tuberculosis
bacteria may be associated: HIV
infection or its treatment could
either interfere with anti-tuberculosis drugs and make them less
effective, or could lead to resistance to these medicines.
patients and drug-resistant
tuberculosis patients may have
similar risk factors such as a shared environment. Indeed, there have
been many outbreaks of drug-resistant tuberculosis in places where
relatively large numbers of HIV-positive people are in close contact
with each other, such as hospitals or prisons. However, information on
how tuberculosis is transmitted in these settings cannot be used to
predict the spread of drug-resistant tuberculosis among the general
5. What is the status of drug-resistant tuberculosis in the different WHO regions?
The number of new TB cases in India is very large.
In Africa, the level of drug-resistant
tuberculosis is low but there could
be many undetected cases among
In most countries in North and South America only a small proportion
of cases of tuberculosis are
drug-resistant. In North America, levels of
drug-resistant tuberculosis are declining. In
South America, Peru, Ecuador and Brazil are the worst
affected countries, with Peru alone reporting one third of all new
multidrug-resistant cases in 2006.
Although limited, data from the Eastern Mediterranean
region indicate moderate levels of
with the majority of new cases emerging in Pakistan.
In most countries of Central and Western Europe,
there is little resistance to
anti-tuberculosis drugs. Some of the
countries in Eastern Europe and
Central Asia have the highest rates of
multidrug-resistant and extensively resistant tuberculosis in the world.
In the Russian Federation, the number and the proportion of tuberculosis
cases that are drug-resistant are increasing considerably.
South East Asia shows a moderate proportion of drug-resistant
tuberculosis cases. However, the
number of new cases of tuberculosis in the region is so large,
particularly in India, that the overall burden of
In the Western Pacific, levels of drug-resistant
tuberculosis are moderate. The vast
majority of cases were reported in China. Particularly high rates of
extensively drug-resistant tuberculosis
have been found in Japan and Hong Kong.
6. Why is it difficult to gather information on drug-resistant tuberculosis?
Traditional skin tests do not detect drug
Source: Greg Knobloch
Collecting reliable information on drug-resistant
tuberculosis is expensive,
time-consuming and technically complicated. In order to monitor the
worldwide spread of drug-resistant tuberculosis over time, it is
necessary to test large numbers of
samples, and the database of
results should include useful information such as the
HIV status of the patients, their
medical history and other background data. This requires sufficient
laboratories to perform
drug resistance testing, staff to
interview and classify patients and a transport network to send samples
for analysis to different laboratories inside and outside the country.
These facilities are expensive and not available in many countries,
particularly those with the highest burden of tuberculosis.
For practical and economical reasons, current survey methods do not
test all cases of TB, which limits the reliability of the results, but
nevertheless give a good indication of drug-resistance levels.
To gather more data and determine trends in countries with a high TB
burden, surveys must be simplified. New, quicker testing techniques
which may help simplify and repeat drug-resistance surveys are currently
Patients need to be registered into a suitable treatment
Source: Gary Hampton
In 2006, approximately half a million new cases of
(MDR-TB) emerged in the world, with
the disease affecting almost every country. The highest proportion of
MDR-TB among all TB cases is found in the former Soviet Union. In
absolute numbers, the worst affected country is China.
Extensively drug-resistant tuberculosis
(XDR-TB) can only be treated with a
handful of drugs that are more expensive and have worse side-effects
than the drugs used to treat
XDR-TB is widespread but is a particularly significant problem in
countries of the former Soviet Union, where cases of extensive
resistance are high both in absolute numbers and as a proportion of
total TB cases.
There is a significant association between
MDR-TB. The death rate in people who
have both infections is high. In order to reduce the number of people
infected with both HIV and MDR-TB
it is important to prevent transmission in places where infected people
are in close contact with each other, such as hospitals and prisons.
Despite progress in information gathering, more laboratories and staff
are still needed to measure the extent of drug-resistant
tuberculosis. The network of
supra-national reference laboratories
must continue to offer practical help while individual countries improve
To control MDR-TB, all countries
need to increase their efforts to prevent transmission, detect cases as
early as possible and register all patients into a suitable treatment
programme. Methods to detect
drug resistance quickly and new
drugs to treat MDR-TB are urgently needed.