HIV update - 11th May 2016

HIV transmission and antiretroviral therapy

Antiretroviral treatment greatly reduces the risk of transmitting HIV. Several very large studies have now shown that people with undetectable viral load do not pass on HIV to their sexual partners. However, there is still a possibility that HIV might be passed on during the period between starting treatment and viral load becoming detectable, which may take up to six months, or if viral load rebounds due to treatment failure.

A review of a large PrEP study conducted in couples where one partner had HIV and the other did not, has shown that when the partners with HIV became eligible to start antiretroviral treatment for their own health, there was still a risk that HIV could be passed on before they reached an undetectable viral load.

The study of 1592 couples found that three infections took place during the first six months on treatment, all from women to their male partners. The study investigators were not able to measure viral load each month or test partners each month. In one case infection almost certainly took place either just before or around the time that treatment was started.

In the other two cases, transmission occurred no later than two and five months after the HIV-positive partner started treatment. In the former case viral load was not measured for the first time until after seroconversion was detected. In the latter case viral load had been measured at three months and had been found to be detectable. Plasma viral load was measured at 872 copies/ml at this time, which is below the level found to be associated with male-to-female transmission in a previous large study.

All three infections were confirmed by testing the genetic linkage between viruses.

The researchers calculated that although the risk of transmission fell somewhat after people started treatment, almost two in a hundred people would become infected during the first six months after their partner started treatment, and the risk did not fall to zero until people had been taking antiretroviral therapy for six months.

The researchers found that 65% of people had undetectable viral load after being on treatment for three months and 85% after six months. After one year on treatment 91% had undetectable viral load.

A sub-set of study participants provided semen samples or swabs from the cervix, in order to test whether viral load was detectable. In people with detectable viral load, HIV was detectable in 21% of semen samples and 12% of cervical swabs. In people with undetectable viral load, HIV was detectable in 9% of semen samples and 8% of cervical swabs, at very low levels.

After starting treatment the rates of self-reported condomless sex and pregnancy both fell significantly.

Taken together these findings indicate that:

• During the first six months on treatment the risk of transmitting HIV was similar to the risk prior to starting treatment. After six months on treatment the risk in this study fell to zero.
• People take varying lengths of time to reach an undetectable viral load. At least one-third of people in this study still had a detectable viral load three months after starting treatment.
• A small proportion of people with undetectable viral load in blood will still have detectable viral load in genital fluids. No infections were seen when people on treatment had undetectable viral load in blood, so it is likely that virus levels in genital fluids were too low to lead to infection.

The researchers say that their findings emphasise the importance of making pre-exposure prophylaxis (PrEP) available to the partners of people starting HIV treatment. The findings also emphasise the importance of consistent condom use until undetectable viral load has been confirmed.

Another study, looking at HIV in pre-ejaculatory fluid (pre-cum), provided reassurance that even when low levels of HIV are present in the semen of men with undetectable viral load in their blood, HIV is not found in pre-ejaculatory fluid. The study looked at 52 men with undetectable viral load in blood. It found that ten men had low levels of detectable HIV in their semen. These levels were below the level found to lead to HIV transmission in male-female couples and were probably a transient `blip` caused by the presence of white blood cells. None of these men had HIV in their pre-ejaculatory fluid.

Sex after HIV diagnosis

To what extent do gay men modify their sexual risk behaviour after testing HIV positive? Two Australian surveys conducted over the last few years have found that in the immediate aftermath of diagnosis, gay men considerably reduce the number of partners they have sex with – many stopping sexual activity altogether – and also reduce the amount of condomless sex they have with partners of unknown HIV status. There was also an increase in HIV status disclosure.

New Australian research shows that the only factor that predicted these changes in sexual behaviour in the months after diagnosis was peer support from other men with HIV (and not from anyone else).

HIV and ageing

Improvements in treatment and care mean that many people with HIV are now living well into old age. Over half of HIV-positive adults in the United States are now aged 50 years and over. Previous research has shown that these patients frequently have multiple health problems and develop conditions associated with old age earlier than the traditional cut-off for old age – 65 years.

Research in San Francisco published recently found a high frequency of age-related problems in people living with HIV over the age of 50. Two-thirds of people who took part in this study were in their 50s, half were receiving disability benefits and the majority were living on incomes well below the average for the city.

Despite good control of HIV infection and high CD4 cell counts, 40% reported difficulties with daily activities, most reported loneliness, many had mild cognitive impairment and 30% had only poor to fair quality of life. 41% reported a fall in the previous year, almost 60% reported loneliness, half reported receiving low levels of social support and over a third met the criteria for mild cognitive impairment.

These findings emphasise how the needs of people living with HIV are changing as the average age of the HIV-positive population rises – and how problems connected to ageing may become apparent in people with HIV at a younger age, probably due to frailty connected to a previous AIDS diagnosis. A recent projection from the Netherlands, where the HIV epidemic has a similar profile to the United Kingdom, predicts that three-quarters of people living with HIV will be over the age of 50 by 2030.

The study also shows the importance to well-being of social support and measures to reduce isolation.