Beliefs about reduced infection risk on ART linked to STI risk

People who believed that having undetectable viral load on antiretroviral therapy reduces the risk of passing on HIV were more likely to have a sexually transmitted infection in a US study, published this week in HIV Medicine.

The study authors, from the University of Connecticut, say that any attempt to expand the use of HIV treatment for prevention purposes will need to address beliefs about infectiousness and aggressively control sexually transmitted infections (STIs).

Sexually transmitted infections increase the risk of transmission from a person with HIV in a number of ways (although it is important to note that viral load increases have not been detected in all patients diagnosed with STIs when genital fluids are studied in people taking antiretroviral drugs):

• HSV-2, the cause of genital herpes, increases viral shedding, especially from lesions.
• Viral load may be raised during early syphilis infection.
• Gonorrhoea, chlamydia and non-specific urethritis may increase viral shedding in the genital tract.

Seth Kalichman and colleagues at the University of Connecticut designed a study to look at the incidence of STIs in people with HIV and their relationship to knowledge of viral load and beliefs about viral load and infectivity.

The study recruited 490 people living with HIV in Atlanta through clinics, social service agencies and AIDS service organisations between 2005 and 2009. Just over two-thirds of the participants were male, 6-10% were transgender and the remainder were women. 90% of participants were African American. Sexuality and gender of sexual partners was unspecified.

At two interviews three months apart participants were asked whether they had been diagnosed with a sexually transmitted infection in the previous three months, a period selected because previous research had found that recall of sexual activity was more reliable within this time-frame. Participants were asked about their sexual behaviour and the number of sexual partners they had.

Participants’ beliefs about infectiousness and treatment optimism, or the future seriousness of HIV infection, were also assessed, by asking participants to indicate their strength of agreement or disagreement with the following statements:

• People with HIV who take HIV medications are less likely to infect their sex partners during unsafe sex
• HIV treatments make it easier to relax about unsafe sex
• It is safe to have sex without a condom if my viral load is undetectable
• People with an undetectable viral load do not need to worry so much about infecting others with HIV

Treatment optimism beliefs:

• New treatments for HIV have brought hope for a cure
• HIV will soon be a controllable disease like diabetes
• There will be a cure for HIV in the next few years

Ten per cent of participants reported having been diagnosed with a sexually transmitted infection at the initial assessment, and a further 4% were diagnosed in the subsequent three months, indicating a high incidence of STIs among the study population, although not out of line with STI incidence in other community samples, the authors note.

The most frequently diagnosed STIs were genital herpes (37%), syphilis (36%), chlamydia (20%) and gonorrhoea (13%). Just under three-quarters reported being diagnosed with multiple STIs in the time since their HIV diagnosis.

Individuals who contracted STIs were younger, had fewer years of education and lower CD4 counts at baseline. They reported a higher number of HIV-related symptoms, and were much less likely to know their most recent viral load measurement (viral load unknown OR 1.5, 95% CI 1.1-2.1). Twenty-two per cent of people diagnosed with STIs had an undetectable viral load, compared to 47% of those not diagnosed with STIs, while roughly equal proportions reported a detectable viral load (33% vs 36%).

Multivariate analysis showed that the following factors were significant predictors of having a new sexually transmitted infection:

• Infectiousness beliefs (adjusted OR 1.32, 95% CI 1.05-1.66, p<0.01): recently diagnosed individuals were more likely to believe that people with undetectable viral load are not infectious.
• Cannabis use (AOR 3.57, 95% CI 1.21-10.55, p<0.05)
• HIV symptoms (AOR 1.17, 95% CI 1.07-1.29, p<0.01)
• Education (AOR 0.85, 95% CI 0.73-0.98, p<0.05)

There was no relationship between treatment optimism score and having an STI.

Although it did not remain significant in the multivariate analysis, initial analysis did show that people diagnosed with an STI had had more sexual partners, regardless of awareness of their own viral load.

However, there was no difference in the frequency of reported serodiscordant unprotected intercourse according to STI diagnosis, which is the critical measure when assessing the potential for onward transmission related to STIs. Indeed, condom use with serodiscordant partners was most frequent among those who had been diagnosed with an STI and knew themselves to have a detectable viral load.

This finding suggests that “people living with HIV take their viral load into account when making sexual decisions,” the authors say.

Although the authors note that their inability to conduct confirmatory testing for STIs was a limitation of their study, they also note that they were unable to test for asymptomatic STIs. This means that the incidence of STIs in the study may have been under-estimated.

“These findings confirm previous research indicating that infectiousness beliefs play a central role in continued transmission risks for some people living with HIV.”

"Scaling up antiretroviral therapy for HIV prevention will therefore only be successful when infectiousness beliefs are reality-based and when co-occurring STIs are prevented, rapidly detected and treated,” they conclude.