A Human Immuno-deficiency Virus (HIV) infection has always
been, in and of itself, a devastating turn of events.
Now, new research hints that an HIV positive diagnosis
can be a canary in the mine, warning of an immediately
elevated risk of acquiring tuberculosis (TB).
While it's been known for some
time that HIV patients are more likely to get TB, it
was widely held that the risk of TB comes long after
the initial HIV infection. However, a study in the January
15 issue of the Journal of Infectious Diseases
suggests that TB is a concern nearly right off the bat.
Mining
the data
The study focused on 23,874 South African gold miners
— 17,766 were HIV negative at the beginning of
the study, 3,371 were HIV positive and 2,737 were known
to have seroconverted (gone from HIV negative to HIV
positive) during the course of the study which covered
a total of almost 54,000 person-years.
There were 740 cases of TB among
the miners, giving an overall incidence of 1.43 cases
per 100 person years. For those miners who were HIV-positive
however, the incidence was much higher — 2.90 cases.
Conversely, in the HIV negative miners, the incidence
was far less, at 0.80 cases.
Unsurprisingly, the incidence of
TB rose with both age and the amount of time that had
elapsed since seroconversion. But the researchers didn't
expect to find the risk of getting TB to double
within the first year of HIV infection. After two years,
the TB risk had quadrupled. After that, the risk continued
growing, but only slightly, for up to seven years after
acquiring HIV.
AN
OUNCE OF PREVENTION
"This study has implications for planners," said lead
author Dr Pam Sonnenberg of the London School of Hygiene
and Tropical Medicine, in an interview with Reuters
Health. "Current models have underestimated the effect
of HIV on TB in the early years after HIV infection.
It may also have implications for the extent to which
TB rates can be reduced by antiretroviral treatment."
The authors wrote that in the case
of the miners, who must work in close quarters with
consumptive colleagues, "innovative interventions, such
as mass chemoprophylaxis with isoniaxid, may be appropriate."
Whether the TB infections were
due to a reactivation of dormant TB-causing bacterium
Mycobacterium tuberculosis, were newly acquired,
or coincidentally involved reactivated and new bacterial
strains remains unclear.
J Infect Dis Jan 15, 2005;191:150-8.
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