High rates of adolescents living with undiagnosed HIV in five high-burden countries

Image by Elizabeth Glaser Pediatric AIDS Foundation/DFID - UK Department for International Development. Creative Commons licence.

High rates of undiagnosed HIV were found amongst adolescents (aged between 10 and 19) across five high-burden countries in southern Africa, while the low rates of undetectable viral loads in those accessing treatment raises concerns around treatment effectiveness. This is the first study to estimate the number of adolescents living with HIV across Zimbabwe, Malawi, Zambia, Eswatini and Lesotho, and is published by Dr Andrea Low of Columbia University in Clinical Infectious Diseases.

Around 60% of adolescents living with HIV are in southern and eastern Africa. The number of children reaching adolescence has increased in the region due to the scale-up of treatment, but adolescents have increasing mortality rates.

The study findings suggest that a major expansion of testing opportunities, support with treatment and optimised treatment is imperative to alleviate this. The authors note that “inadequate case finding and high-rates of treatment attrition” contribute to the poor outcomes for adolescents.



Relating to the period around the time of birth. Perinatal transmission is when HIV is passed on during pregnancy, childbirth or breastfeeding. People with perinatally-acquired HIV have been living with HIV since birth or infancy.

perinatally infected

A person who was perinatally infected with HIV has had the virus since birth.


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.


Of or relating to children.


Relating to the period starting a few weeks before birth and including the birth and a few weeks after birth.

Nationally representative surveys (Population-based HIV Impact Assessments) were designed to measure HIV-related indicators. They were conducted between 2015 and 2017. In total, 109,970 adults and children took part, including 24,805 adolescents.

The survey was completed by household members over the age of 10 who agreed to be interviewed and provide samples for testing (rapid HIV testing, CD4 count, viral load, detection of antiretrovirals and recent HIV infection). Undetectable viral loads were classed as those under 50 copies.

Older adolescents (aged 15 to 19) answered the adult questionnaire which included questions on sexual behaviour and clinical history. Younger adolescents (aged 10 to 14) answered the adolescent questionnaire which covered sexual history, except in Malawi. Clinical history for younger adolescents was provided by parents or guardians.

A risk algorithm was used to classify the most likely mode of HIV acquisition. For example, an adolescent who had a biological mother who tested HIV positive would be classified as perinatally infected. An adolescent with a recent infection would be classified as behaviourally infected.

Key results

Almost 40% of the HIV-positive adolescents were living with undiagnosed HIV. Zambia had the lowest adolescent HIV prevalence rate at 1.6%, but it had the highest proportion of undiagnosed adolescents at 60%. Eswatini had the highest HIV prevalence rate at 4.8%, but the lowest undiagnosed rate at 22%.

HIV prevalence was higher among older adolescents in every country, except Malawi. Rates of HIV prevalence were significantly higher in orphans (9.5%) than those with at least one living parent (1.8%).

Of the participants who reported being already diagnosed with HIV, 92% reported receiving treatment or had detectable antiretrovirals in their blood. The authors noted high levels of discordance between the self-reported status and detectable antiretrovirals amongst young people. This was greater than among adults, which they felt could be linked to stigma and discrimination.

Only a third of adolescents had an undetectable viral load and just two-thirds of adolescents with detectable antiretroviral levels had an undetectable viral load. This was lowest in Malawi, where only 57% of those with detectable antiretroviral levels had an undetectable viral load. Fewer than half of the young adolescents in Malawi had an undetectable viral load.

Depending on how mode of acquisition was assessed, between 55 and 73% of adolescents were perinatally infected with HIV, while 27 to 45% of adolescents were behaviourally infected with HIV.

Outcomes for adolescents with behaviourally infected HIV were consistently poorer than those with perinatally infected HIV. Just 41% of adolescents with behaviourally infected HIV had a prior HIV diagnosis. Significantly higher numbers of adolescents with perinatally infected HIV had a prior diagnosis at 70%. HIV testing is less accessible for adolescents than for adults, due to legal issues about consent and disclosure and generally having fewer opportunities to engage with health services than adults.

Overall, 34% of adolescents living with behaviourally infected HIV and 65% of adolescents living with perinatally infected HIV reported antiretroviral therapy use. Adolescents with perinatally infected HIV started treatment at a median age of nine. Those with behaviourally infected HIV started at a median age of 15.

Of those taking treatment, 63% of adolescents living with perinatally infected HIV had an undetectable viral load, compared to just 52% of adolescents living with behaviourally infected HIV. The low rates of HIV status awareness and undetectable viral loads among adolescents living with behaviourally infected HIV indicate a need for targeted testing and services to support them.


The study results provide a comprehensive picture of the burden of HIV among adolescents. Inadequate adherence is reflected in poor retention in care and low rates of viral load suppression. This shows the significant challenges of providing optimal paediatric care in resource-limited settings.

Large proportions of perinatal infections reflect the challenges in scale-up of early infant diagnostic services. The authors note the “limited availability of testing in paediatric care or adolescent-friendly testing services, as well as gaps in index testing of family members of HIV-positive adults.” For example, 30% of those with perinatal infection were untreated but had survived into adolescence. The authors suggest “innovative strategies for adolescents should be further explored” to improve case identification.

The findings highlight the need to provide optimised treatment regimens and provide adherence support. The authors suggest a need for tailored services for adolescents, including mental health screening, diagnostics for co-morbidities and specialised interventions that recognise the long-term impact of untreated infection as they grow into adulthood. “Rapid transition to more optimal regimens, tailored adherence support, and timely management of elevated viral load with a switch to second-line therapy could help improve viral load suppression in this population,” say the authors.


Low A et al. Human Immunodeficiency Virus Infection in Adolescents and Mode of Transmission in Southern Africa: A Multinational Analysis of Population-Based Survey Data. Clinical Infectious Diseases, online ahead of print, ciab031, 29 April 2021 (open access)


Full image caption: Image by Elizabeth Glaser Pediatric AIDS Foundation/DFID - UK Department for International Development. Available at www.flickr.com/photos/dfid/5181913478 under Creative Commons licence CC BY-NC-ND 2.0.