The San Francisco City Department of Public Health assessed
what proportion of people diagnosed each year since 2008 still had a viral load
above 1500 copies/ml a year later and how much time they spent with a viral
load above 1500 copies/ml in the year after diagnosis.
The cut-off point of 1500 copies/ml was chosen as the level
above which HIV transmission becomes more likely; a study in Uganda found no
cases of HIV transmission in couples where one partner had HIV over a 30-month
follow-up period if the HIV-positive partner had a viral load below 1500
They also looked at the proportion of time spent with viral
load above 200 copies/ml or with viral load above 10,000 copies/ml.
Using the city’s HIV surveillance registry, the
investigators included everyone diagnosed with HIV between 2008 and 2016 who
had at least two viral load test results in the first year after diagnosis.
Using these data, they calculated what proportion of the
first year after diagnosis was spent with a viral load above 200 copies/ml,
above 1500 copies/ml or above 10,000 copies/ml.
A total of 2256 people were diagnosed with HIV between 2008
and 2016, 73% men who have sex with men (MSM), 12% MSM who inject drugs and 7% other people
who inject drugs.
Twenty-four per cent of those diagnosed had no recorded antiretroviral therapy
after diagnosis and 20% took between three months and one year to start. The
remainder started treatment within three months of diagnosis.
In 2008, people diagnosed with HIV spent 46% of the first
year after diagnosis with viral loads above 10,000 copies/ml and 62.3% with viral loads above 1500 copies/ml.
In 2010, the San Francisco Department of Public Health
introduced a policy of offering treatment immediately after diagnosis.
A sharp decline in the proportion of time spent with
detectable viral load was evident by 2012, when people diagnosed with HIV spent
28% of the year after diagnosis with viral loads above 10,000 copies/ml and 39%
of the time with viral loads above 1500 copies/ml.
By 2016, people diagnosed in that year spent only 17% of the
first year after diagnosis with viral loads above 10,000 copies/ml and 24.8% of
the time with viral loads above 1500 copies/ml.
Multivariate analysis showed that MSM who inject drugs, the
homeless and, unsurprisingly, people who started treatment more than three months
after diagnosis all had longer durations of detectable viral load (> 200
copies/ml). Young people aged 25 to 29 also had a slightly higher risk of
more prolonged detectable viremia. The study found no racial differences in duration
of detectable viremia.