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November 3,
2007
Cape Town -
Health systems cannot properly
diagnose, treat, or contain the
co-epidemic of HIV and tuberculosis
(TB) because not enough is known about
how the two diseases interact.
A report by
leading global health experts warned
that the largely "unnoticed
collision" of the global
epidemics of HIV and TB has exploded
to create a deadly co-epidemic that is
rapidly spreading in sub-Saharan
Africa.
Approximately
one-third of the world's 40 million
people with HIV/AIDS are co-infected
with TB, and the mortality rate for
HIV-TB co-infection is five-fold
higher than that for tuberculosis
alone.
This situation
is made yet more urgent by the surging
rates of multi-drug resistant (MDR) TB
in some areas with high HIV
prevalence, according to the report
compiled by the Forum for
Collaborative HIV Research, a global
independent partnership comprised of
researchers, patient advocates,
government and industry
representatives.
"The eye of
the storm is in sub-Saharan Africa,
where half of new TB cases are HIV
co-infected, and where drug-resistant
TB is silently spreading," said
Veronica Miller, co-author of the
report and director of the Forum.
"Unlike
bird flu, the global threat of HIV/TB
is not hypothetical. It is here now.
But the science and coordination
needed to stop it are utterly
insufficient."
The report
details several of the most urgent
problems in need of accelerated
research:
Diagnosis
of HIV-TB
In many clinics,
HIV can be reliably diagnosed in as
little as 15 minutes using a simple
test. In contrast, the standard
diagnostic test for TB, invented 120
years ago, fails to detect between 40
percent to 80 percent of TB cases in
those with HIV-TB. While a more
advanced sputum culture test exists, a
lack of laboratory facilities means
the test is unavailable for the
overwhelming majority of patients in
Africa. Even when it is available,
results typically take many weeks to
obtain. During that time, people with
active TB, including MDR- and XDR-TB,
may unknowingly spread their
infection.
Detection of TB
is further complicated by atypical
symptoms in people who are
co-infected. In co-infection, TB is
less likely to cause typical lung
disease and more likely to cause
"disseminated TB," affecting
almost any organ of the body. This
makes standard chest x-rays much less
useful for diagnosis.
TB in
HIV-Infected Children
Almost
one-quarter of HIV-infected children
develop TB every year and
drug-resistant TB among children is
increasing. Many unanswered questions
remain in the diagnosis and treatment
of pediatric HIV-TB co-infection, and
there is a lack of pediatric drug
formulations for both TB and HIV
drugs. Despite all this, very few
clinical trials of childhood TB have
been conducted to optimize diagnosis
or treatment outcomes.
"Nearly
every infant with HIV suffers from
pneumonia. TB also causes acute
pneumonia, but with our current tools
it is hard to know what is and is not
caused by TB," said Mark Cotton,
a pediatrician and HIV researcher at
Stellenbosch University.
"Children should be included in
trials to evaluate new anti-TB
drugs."
A further cause
for concern is the use of the Bacille
Calmette-Guérin (BCG) vaccine in
children, the report says. The vaccine
provides some protection against
disseminated TB in children.
Therefore, based on WHO
recommendations, BCG is given once at
birth in most developing countries.
But recent studies have found high
rates of BCG disease and related
deaths in HIV-infected infants who
have received the vaccine, and WHO has
issued an advisory note regarding the
use of BCG in HIV-infected children.
"One study
found a 75 percent mortality rate in
children with BCG disease, and 70
percent of those children were
HIV-infected. Clearly, this is a
problem in need of immediate
attention," Cotton said.
Infection
Control
A medicine that
appears to prevent active disease in
HIV/TB co-infected patients, thus
aiding infection control, is
practically unused for this purpose,
says the report. The medicine,
Isoniazid, is a front-line drug used
to treat TB. But concerns about
Isoniazid Preventive Therapy (IPT) are
such that Botswana is the only country
in sub-Saharan Africa to use IPT
nationally. These concerns include the
potential for IPT-related drug
resistance, the short duration of IPT
efficacy, and the difficulties in
ruling out active TB in co-infected
people.
"Research
that definitively addresses these
concerns is needed now, in order to
make this tool available or come up
with alternatives to control the
spread of infection," Stephen
Lawn, a medical researcher at the
University of Cape Town, said.
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