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HIV/AIDS
New high-risk populations emerge
as the virus continues to spread
BY Alexandra de Pokomandy, MDCM
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Twenty-five years after its discovery, the
Human Immunodeficiency Virus (HIV) still fuels an epidemic that
is far from over. Of the almost 40 million people worldwide who
are infected with HIV today, 25 million live in Sub-Saharan Africa,
where the overall prevalence is as high as 5.9%, with an estimated
2.1 million deaths from AIDS in 2006.1
In Canada, the prevalence of HIV infection is 0.2%, i.e. 58,000
people currently live with it.2
Over the last decade, around 2,500 new HIV infections were registered
each year in Canada, and it's estimated that up to a third of infected
individuals are unaware of their status.3
Although there's no firm evidence of a rising incidence of HIV in
Canada, it certainly doesn't seem to be decreasing.
Who's
at risk of acquiring HIV?
There's been a recent shift in exposure risk to HIV infection,
as illustrated in Figure
1. Although men having sex with men continue to make up the
largest group of new infections (45% in 2005 in Canada), other risk
categories are rapidly increasing in importance, with women now
representing 25% of recent infections. While it was initially considered
low risk, heterosexual contact with people from non-endemic areas
is the exposure category which has increased most dramatically in
the past years, representing 21% of all new HIV infections in 2005.2
People from HIV-endemic countries continue to make up a disproportionately
large fraction of new cases, which may partly be explained by the
Canadian immigration policy -- established in 2002 -- requiring
all immigrants and refugees to be tested for HIV as part of their
medical evaluation.4 In contrast,
intravenous (IV) drug use has decreased in importance as a cause
of HIV infection since 1996, now representing 14% of new cases.
Of concern is the increasing incidence observed among aboriginal
populations -- most of these infections are transmitted through
IV drug use or heterosexual contact.2
Who
should be screened?
Anyone requesting HIV screening or presenting with risk factors
for transmission, such as people with more than 2-5 sexual partners
in the past year, men or women who had a sexual partner from an
endemic country, street youth, drug users (IV or not), men having
sex with men, sex workers, people with blood exposures through non-sterile
techniques (e.g. tattooing, piercing), individuals who received
blood transfusions before 1985 in Canada or at anytime in other
countries, and all pregnant women should be screened for HIV. The
frequency of screening should be determined by the extent of the
behaviour, and can be performed at fixed intervals or as needed,
based on the assessment of clinical risk. Anyone presenting with
symptoms of HIV, such as opportunistic infection, tuberculosis or
fever of unknown origin, should also be investigated. Keep in mind
that there's a period of 3-6 months after exposure during which
HIV antibodies may not be detectable yet.
How
do we recognize primary infection?
A recent study in Quebec demonstrated that most transmissions
occur during primary HIV infection.5
Approximately 40-90% of patients are symptomatic during this phase.
Unfortunately, most diagnoses are missed because the presentation
is similar to other viral illnesses. Signs and symptoms of acute
HIV infection may last only 1-2 weeks, but can persist for up to
several months. Fever is generally the hallmark, occurring in 96%
of patients. Other potential signs include lymphadenopathy (74%),
pharyngitis (70%), rash (70%), myalgias (54%), diarrhea (32%), headache
(32%), nausea and vomiting (27%), hepato-splenomegaly (14%), weight
loss (13%), thrush (12%) and neurological manifestations (12%).6
Patients with these symptoms should be questioned for high-risk
behaviour and -- if risk factors are present -- tested for HIV antibodies
(serology by enzyme immunoassay [EIA] and Western Blot) and HIV
RNA (viral load) and/or antigen p24. Acute or primary HIV infection
is characterized by a negative or undetermined HIV serology with
an HIV viral load > 10,000 copies/mL or a positive antigen p24.
A viral load < 10,000 copies/mL would be a false positive in
this context; viral loads in primary HIV infection are generally
well above 100,000 copies/mL. Serology ought to be repeated a few
weeks later to confirm seroconversion.
What's
the protocol after a positive test?
When a patient is diagnosed with HIV infection, the doctor
should be prepared to provide counselling, support and rapid referral.
As stated in most guidelines,6,7
it's not recommended that primary care physicians follow their HIV-infected
patients without a consultant. HIV expertise is often defined as
following at least 20, and ideally 50 HIV-infected patients. Most
provinces have specialized centres to which you can refer, where
multidisciplinary resources are available.
There's currently a debate as to whether or
not we should treat primary infection. The hypothesis is that early
treatment could improve the set point where the CD4 (T-cell) counts
and HIV viral load will stabilize in chronic infection, which could
alter disease progression. Currently, data are still insufficient
to draw any conclusions, but patients will benefit from participating
in a primary HIV infection observational study. The primary care
provider is advised to refer these individuals to such studies --
if available where they live.
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