People with HIV who are undiagnosed and those with detectable viral load less likely to use condoms, South African study finds

People with HIV who don't use condoms consistently are more likely to be unaware they are HIV-positive or to have a detectable viral load when their HIV infection has been diagnosed, according to research conducted in South Africa and published in Nature Scientific Reports.

“We found that those unaware of their HIV-positivity were more likely to report higher risk behaviour than those aware,” write the authors. “A novel finding of this study was that higher risk behaviour was also associated with higher viral loads in those who were aware of their HIV-positivity.”

Researchers found that only 7 out of 165 people with HIV who reported more than one sexual partner in the previous year had used condoms consistently, leading them to define multiple sexual partnerships as high-risk behaviour.


risky behaviour

In HIV, refers to any behaviour or action that increases an individual’s probability of acquiring or transmitting HIV, such as having unprotected sex, having multiple partners or sharing drug injection equipment.

adjusted odds ratio (AOR)

Comparing one group with another, expresses differences in the odds of something happening. An odds ratio above 1 means something is more likely to happen in the group of interest; an odds ratio below 1 means it is less likely to happen. Similar to ‘relative risk’. 

detectable viral load

When viral load is detectable, this indicates that HIV is replicating in the body. If the person is taking HIV treatment but their viral load is detectable, the treatment is not working properly. There may still be a risk of HIV transmission to sexual partners.

cross-sectional study

A ‘snapshot’ study in which information is collected on people at one point in time. See also ‘longitudinal’.

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

The investigators believe these findings have implications for the reliability of modelling studies showing the potential of expanded testing and antiretroviral treatment to control the HIV epidemic in South Africa.

They also highlight the fact that sexual behaviour likely to lead to onward HIV transmission was associated with poor health-seeking behaviour: either lack of awareness of HIV status or lack of engagement in HIV care. Understanding the reasons why people choose not to seek diagnosis or care will be essential not only for expanding treatment but also for reducing HIV transmission.

The cross-sectional study was conducted in KwaZulu-Natal, which has one of the highest adult HIV prevalence rates in the world (28%) and where HIV incidence remains high (2.6 infections per 100 person-years). Researchers hypothesised that people with higher risk sexual behaviour were less likely to know their HIV status and to be virally suppressed.

They therefore designed a survey involving adults aged between 15 and 59 years. Participants were interviewed about their sexual behaviour. Individuals were tested for HIV if they did not already know they were positive. Blood samples were obtained to check viral load and for the presence of antiretroviral drugs. The study was conducted between July and October 2013.

The total study population consisted of 5649 individuals of whom 1423 were HIV-positive and therefore included in the present analysis. Median age was 34 years.

Thirty-five per cent of people with HIV reported inconsistent condom use with a single partner in the previous year. 11.6% reported having multiple sexual partners and only 7 of 165 reported consistent condom use.

Concurrent sexual relationships were reported by 12% of individuals and 4% reported casual and/or transactional sex. Men were more likely than women to have had more than one sexual partner, a concurrent relationship and casual or transactional sex.

A quarter of people with HIV were unaware of their infection status and 43% of all those with HIV had a viral load above 1000 copies/ml. Unawareness and a high viral load were both more common among men than women.

Unawareness was strongly associated with having multiple sexual partners during the preceding year. Among people reporting more than one sexual partner in the previous year, 45% were unaware they were HIV-positive compared to 22% reporting a single partner. 

Inconsistent condom use in the previous year was strongly associated with having more than one sexual partner (women, aOR = 9.6, 95% CI, 3.4-26.9; men, aOR = 23.6, 95% CI, 7.1-78.4) and unawareness of being HIV-positive (women, OR, 3.4, 95% CI, 2.2-5.2; men, aOR, 4.1, 95% CI, 2.0-8.7).

Overall, 29% of men had more than one sexual partner; 96% of these individuals reported inconsistent condom use; 52% had a viral load above 1000 copies/ml and 35% a viral load above 100,000 copies/ml. The proportion of men virally unsuppressed rose with increasing risky sexual behaviour from approximately 30% for men with the least risky sexual behaviour (no sex in the preceding year) to over 70% for those with the greatest level of risk behaviour (inconsistent condom use and more than one partner in the preceding year).

When the investigators limited their analysis to men who were aware they were HIV-positive, they still found that men with a high viral load were the group most likely to report high-risk behaviour (21% lower risk vs. 56% higher risk).

In women, the risk of transmitting HIV was mainly linked to viral load. Overall, 9% of women reported more than one sexual partner; 94% of these women reported inconsistent condom use and 40% had a viral load above 1000 copies/ml, with 24% having a viral load above 100,000 copies/ml. The proportion with a high viral load increased with risk behaviour, from 32% for those with the lowest risk to 56% for those reporting the riskiest sex. Analysis of women who were aware they were HIV-positive showed that only 4% of those reporting more than one partner had a viral load above 1000 copies/ml.  

“There is a clear need to target HIV prevention interventions, including HIV testing campaigns and treatment programmes, to different groups of people based on risk factors associated with their sexual behaviour, as well as explore alternative retention and adherence strategies,” conclude the investigators. “However, such relationships are unlikely to be shifted by a purely health sector-driven approach and innovative strategies, driven by epidemiological and anthropological evidence, need to be developed to enable more comprehensive approaches to HIV prevention.”


Huerga H et al. Higher risk sexual behaviour is associated with unawareness of HIV-positivity and lack of viral suppression – implications for Treatment as Prevention. Scientific Reports, 7: 16117, doi: 10.1038/s41598-017-16382-6 (2017)