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Individuals with recent HIV
infection are sustaining the epidemic, a Swiss study published in the online
edition of AIDS suggests. The investigators believe that their results further
support the use of antiretroviral therapy as prevention, but also show that its
impact on the epidemic will be blunted because of the high number of
transmissions which can be attributed to individuals who have been recently
infected with HIV and who are not yet taking treatment.
Phylogenetic analysis showed that
only a handful of infections in individual diagnosed between 2008 and 2010
could be attributed to patients diagnosed before 2000. Patients with
longer-term HIV infection were the group most likely to be taking antiretroviral
therapy and to have an undetectable viral load.
“Recent HIV infections were a
significant source of HIV spread,” comment the authors. “By contrast, HIV
individuals diagnosed before 2000 were rarely the source of new infections
before 2008.”
It is now widely accepted that
patients who are taking HIV therapy that suppresses their viral load to
undetectable levels are highly unlikely to transmit the virus to their sex
partners.
However, even in countries with
widespread free access to antiretrovirals there continue to be large numbers of
new infections.
A possible reason could be that many
of these transmissions originate in individuals who have only recently been
infected with HIV. Many of these patients will be unaware that they have HIV
and few will be taking anti-HIV drugs.
The molecular epidemiology of the
HIV epidemic in Geneva, Switzerland, has been studied in detail since the
1990s. A retrospective analysis of blood samples obtained from patients
diagnosed in three periods (before 2000; 2000 to 2008; and 2008 to 2010) allowed
investigators to establish if the epidemic was indeed being sustained by
individuals with more recent infection.
Phylogenetic analyses were performed on 780
newly diagnosed individuals between 2000 and 2010 (142 between 2008 and 2010)
and 1058 patients diagnosed before 2000. This type of analysis is able to
identify clusters of HIV transmissions.
A total of 214 clusters were found, their size
ranging from two to 13 infections. Some 35 clusters included at least one
individual diagnosed between 2008 and 2010.
Overall, 42% of patients diagnosed in the period 2008 to 2010 could be
placed within a cluster.
Almost two-thirds (65%) of patients
diagnosed between 2008 and 2010 belonged to new clusters of infections, and 41%
belonged to clusters exclusively composed of patients diagnosed in this most
recent time period. Just over half of the infections belonged to transmission
network involving patients diagnosed between 2000 and 2008. Only 8% belong to
clusters where all the other members were diagnosed before 2000.
The investigators then conducted an
analysis to see what proportion of patients in each time period belonged to a
transmission cluster which involved individuals diagnosed between 2008 to 2010.
Overall, 66% of patients diagnosed
between 2008 and 2010 could be placed with such a cluster. This compared to
just 2% of all patients diagnosed before 2000.The transmission dynamics
revealed by the authors appeared to be related to the likelihood of each group
of patients taking antiretroviral therapy and having an undetectable viral
load.
Some 84% of individuals diagnosed
before 2000 were taking anti-HIV drugs and 50% had an undetectable viral load.
Three-quarters of individuals
diagnosed between 2000 and 2008 were taking HIV therapy and 42% were undetectable.
In contrast, 51% of patients diagnosed in the most recent time period were
treated with antiretrovirals and only 7% had a viral load below the limit of
detection.
Median viral load also differed
between the three groups of patients and was significantly higher for patients
diagnosed between 2008 and 2010 (p = 0.001).
“We show that the epidemic is only
marginally fed by individuals diagnosed over a decade ago,” comment the
researchers. “This may be related to their lower viral load as a consequence of
HAART coverage…by contrast, recently infected, untreated individuals are a
frequent source of new infections in Geneva.”
The investigators believe that
prevention campaigns need to be focused “on improving diagnosis for recently
infected individuals who represent an important source of HIV transmission.”
They caution that unless measures to increase testing and earlier diagnosis are
not implemented then the ability of HIV treatment to contain the epidemic will
be blunted.
The Friends of AIDS Foundation is
dedicated to enhancing the quality of life for HIV positive individuals and
empowering people to make healthy choices to prevent the spread of the HIV
virus. To learn more about The Friends of AIDS Foundation, please visit: http://www.friendsofaids.org.
TOGETHER WE REMAIN STRONG!
