Testing and Expanded Treatment Linked to Reduce HIV Incidence in San Francisco,
Washington DC, and Vancouver
More widespread HIV testing and early antiretroviral
therapy (ART) not only have clear benefits for the treated
individual, but may also benefit the larger community by reducing
the number of new HIV infections, according to 3 studies from
North America presented at the 17th Conference on Retroviruses
and Opportunistic Infections (CROI
2010) last month in San Francisco.
Effective ART that suppresses viral load to an undetectable level dramatically
reduces the risk of forward HIV transmission. Mathematical models suggest
that universal voluntary testing and widespread treatment -- either
to current guidelines or for everyone
infected regardless of CD4 cell count -- could essentially halt
the spread of the epidemic, but it is not yet clear how well this would
work in the real world.
The 3 studies presented at CROI give the first indication that expanded
testing and treatment are viable and can help reduce the spread of the
disease in high-income countries with overall low prevalence (though
specific areas may have pockets of high prevalence).
Das-Douglas (Photo by Liz Highleyman)
first study, Moupali Das-Douglas from the San Francisco Department of
Public Health and colleagues looked at the effect of community viral
load -- or viral load across an entire community -- on HIV incidence.
They hypothesized that the recent decrease in community viral load in
San Francisco would be associated with a reduction in new HIV infections.
The researchers used San Francisco's comprehensive HIV/AIDS surveillance
system, which includes mandatory reporting of viral load data, as well
as a CDC mathematical model of new infections to calculate community
viral load, and to examine associations between community viral load
and new HIV cases between 2004 and 2008.
at 2 different measures of community viral load: total community viral
load was defined as the sum of the most recent viral load measurements
from all reported HIV+ individuals in a particular population. Mean
community viral load was defined as the average of the most recent viral
load measurements, that is, the sum divided by the number of people.
New HIV cases consist of 3 groups: people who received a new diagnosis
of an existing HIV case (e.g., due to stepped-up testing capturing a
backlog of previously infected but untested individuals), new reports
of existing cases, and HIV incidence, or people who actually were recently
infected. "We really don't have a very precise method of determining
incidence," Das-Douglas noted.
remaining stable at about 23,000-24,000 copies/mL during 2002-2005,
mean community viral load started to fall, reaching 15,000 copies/mL
in 2008, a 40% drop.
decline was associated with a significant decrease in new HIV cases,
from 796 in 2004 to 434 in 2008, approaching a 50% decline.
number of people estimated to be infected but unaware of their status
also fell considerably, from 24% to 15%.
new or recent infections (according to the mathematical model) fell
by about one-third between 2006 and 2008 (from 930 to 620 people),
but this did not reach statistical significance.
the end of the study period, an estimated 80% of newly diagnosed
people were linked to care, about 90% of these were on ART, and
about 75% of treated people had achieved undetectable viral load.
antiretroviral treatment options and coverage, as well as increasing
HIV status awareness," may have led to decreases in community viral
load in San Francisco during the study period," the investigators
concluded. "Findings support the hypothesis that wide-scale early
ART can have a preventive effect at a population-level."
Because community viral load is "temporally upstream" of new
HIV infections, public health departments should consider adding it
to routine HIV surveillance to track the epidemic and evaluate the effectiveness
of HIV prevention and treatment interventions, they suggested.
Speaking at an accompanying press conference, Das-Douglas described
community viral load as a "virometer," or a way to take the
temperature of a community. In response to a question, she noted that
the decline in HIV cases occurred even as rates of other sexually transmitted
infections rose, suggesting that people may be practicing serosorting
(having sex only with partners of the same HIV status).
helps us see how well treatment is working, but also how well prevention
is working, so can target interventions to those at highest risk,"
she said. "What gets measured gets managed."
Amanda Castel from George Washington University School of Public Health
and Health Services and colleagues reported findings from an analysis
of the effect of increased testing in Washington, DC, which has the
highest HIV/AIDS rate in the U.S. -- an estimated 3% overall seroprevalence.
In 2006, the DC Department of Health launched an initiative to promote
routine HIV testing with improved linkage to care throughout the city
(following the newly implemented CDC testing guidelines). This included
opt-out testing at medical facilities, community campaigns to encourage
testing, and testing and treatment in jails.
The researchers assessed trends in the number of HIV tests performed,
the number of people treated, clinical indicators (CD4 cell count and
HIV viral load) at the time of HIV diagnosis, and changes in numbers
of new cases from 2004 to 2008.
number of HIV tests performed annually rose dramatically, from about
20,000 in 2004, to 35,000 in 2006 at the start of the testing push,
to 93,000 in 2009.
number of HIV diagnoses (according to name-based reporting) increased
significantly, from about 1093 in 2004 to 1280 in 2007 (the last
year with complete data), a decrease of 17%.
testing shortened the mean time between estimated date of infection
percentage of people diagnosed with AIDS who did not learn their
status until they developed advanced disease fell from 66% in 2004
to 57% in 2008.
CD4 count at the time of diagnosis increased significantly, from
216 cells/mm3 in 2004 to 343 cells/mm3 in 2008, or by nearly 60%.
percentage of people who developed symptomatic AIDS within 1 year
after diagnosis decreased from 47% in 2004 to 28% in 2008.
percentage of newly diagnosed individuals accessing care rose from
about 75% in 2004 to about 95% in 2008.
routine HIV testing in Washington, DC has been associated with increased
identification of HIV/AIDS cases, more rapid entry into care as measured
by time to initial CD4 count, percent or viral load, and earlier diagnosis
as indicated by the initial CD4 count itself, and the decreasing proportion
of late testers among AIDS cases," the researchers continued. "Continued
surveillance will help determine whether these findings will translate
into improved clinical outcomes and reduced HIV transmission."
Finally, Julio Montaner from the British Columbia Centre for Excellence
in HIV/AIDS and colleagues looked the link between expanded ART coverage,
community viral load, and decreased HIV transmission among injection
drug users (IDUs) in the Downtown Eastside district of Vancouver, thought
to be the area with the highest HIV/AIDS rate in Canada. The researchers
provided results for the entire province of British Columbia, but overall
rates largely reflect the situation in urban Vancouver.
ART (and medical services in general) are available free of charge for
all British Columbia residents. A targeted effort to expand ART use
among IDUs was started in 2007. HIV testing, ART distribution, and HIV
viral load measurements in the province are centralized, allowing the
researchers to obtain comprehensive data from administrative and medical
number of HIV tests performed in British Columbia annually rose
from 104,229 in 1994, to 137,980 in 1996 (the first years of the
new program), to 182,151 in 2008.
HIV diagnoses in British Columbia dropped overall from 1996 to 2008,
but the annual decrease plateaued in the early 2000s, before commencing
a slower second decline, falling from 440 cases in 2004 to 370 in
rate of new diagnoses among IDUs specifically, however, continued
to decline steeply, falling from 150 in 2004 to 80 in 2009.
number of people receiving ART doubled from about 2500 in 2000 to
about 5000 in 2009.
community viral load declined over the same period, with the proportion
with > 50,000 copies/mL decreasing and the percentage with <
500 copies/mL increasing (from about 40% in 2004 to about 75% in
too, rates of other sexually transmitted infections increased even
as HIV cases declined.
findings, the researchers concluded, "demonstrate an association
between expanded [ART] coverage, decreased provincial plasma viral load,
and decreased new HIV diagnoses," which were temporally related
to a treatment outreach effort targeting IDUs. Montaner suggested the
decrease was likely due to more ART use rather than behavior change,
since needle exchange and other harm reductions were widely implemented
well before the decline began.
Taken together, while these studies cannot prove a causal link between
increased testing, more widespread treatment, reduced community viral
load, and the rate of new HIV infections, they do suggest that expanded
access to testing and care is providing community-wide benefits.
Abstract 33: San Francisco Department of Public Health, San Francisco,
CA; University of California, San Francisco, CA.
Abstract 34: George Washington University School of Public Health and
Health Services, Washington, DC; HIV/AIDS Admin, District of Columbia
Dept of Health, Washington, DC.
88LB: British Columbia Centre for Excellence in HIV/AIDS, Vancouver,
P Chu, G-M Santos, and others. Decreases in Community Viral Load Are
Associated with a Reduction in New HIV Diagnoses in San Francisco. 17th
Conference on Retroviruses & Opportunistic Infections (CROI 2010).
San Francisco. February 16-19, 2010. Abstract 33.
R Samala, A Griffin, and others. Monitoring the Impact of Expanded HIV
Testing in the District of Columbia Using Population-based HIV/AIDS
Surveillance Data. 17th Conference on Retroviruses & Opportunistic
Infections (CROI 2010). San Francisco. February 16-19, 2010. Abstract
E Wood, T Kerr, and others. Association of Expanded HAART Coverage with
a Decrease in New HIV Diagnoses, Particularly among Injection Drug Users
in British Columbia, Canada. 17th Conference on Retroviruses & Opportunistic
Infections (CROI 2010). San Francisco. February 16-19, 2010. Abstract