Over 40% of Ugandan mothers whose infants acquired HIV were only diagnosed while breastfeeding

More than four in ten mothers of infants who acquired HIV in Uganda were not diagnosed until they were already breastfeeding, according to a national clinical audit presented this week at the 26th International AIDS Conference (AIDS 2026) in Rio de Janeiro.

Linda Nabitaka of Uganda's Ministry of Health told the conference that the country routinely audits infants who acquire HIV vertically to identify the programmatic gaps that allow transmission to continue. Her team reviewed 754 records of infants diagnosed with HIV between July 2021 and September 2025 from 47 health facilities across the country, and analysed the 365 records that were complete. The audit drew on antenatal registers, HIV-exposed infant registers and the charts of mothers and infants, looking at the timing of maternal diagnosis, viral load, partner testing, infant prophylaxis and treatment, retention and delivery.

They found that 43% were first diagnosed with HIV while breastfeeding, 21% had been diagnosed before becoming pregnant, 15% during antenatal care and 2% during labour and delivery. The timing of diagnosis was not recorded for 19%, but Nabitaka said many of those with missing information had also been diagnosed for the first time while breastfeeding.

The high proportion diagnosed during breastfeeding reflects Ugandan guidelines, which call for HIV testing every three months until breastfeeding ends. Asked whether women diagnosed during breastfeeding had acquired HIV after an earlier negative test, Nabitaka said the audit did not capture this detail. However, she estimated that around half had tested negative during antenatal care and were not tested again until they were breastfeeding.

Other gaps were also evident. Of the 365 mothers, 71% did not know their partner's HIV status, while only 37% had ever had a viral load test. Among those who had been tested, 29% were not virally suppressed. Infant prophylaxis was documented for only 51% of infants.

Almost 90% of the infants were started on treatment after diagnosis. Among those who were not, the main reasons were death (41%), transfer to another facility (28%) and loss to follow-up (21%). Caregiver refusal accounted for 3%.

Nabitaka identified late maternal diagnosis, limited viral load monitoring and suppression, unknown partner status, and gaps in infant prophylaxis and treatment as key drivers of vertical transmission.

"Expanding the ability to do point-of-care viral load testing for mothers and improving viral suppression is very important, as it's the biggest driver of infant infection,” she said. “Increasing partner HIV testing through assisted partner notification, even for the mothers that are HIV negative, is also important, because it's what leads to maternal seroconversion later in pregnancy and during breastfeeding."

What will it take to end paediatric HIV?

The Ugandan data speak directly to a question posed at a satellite session organised by the Elizabeth Glaser Pediatric AIDS Foundation (EGPAF): why are infants still acquiring HIV in 2026?

"We have known for more than 20 years how to prevent vertical transmission. The science is certainly not a bottleneck," said Dr Doris Macharia, president of EGPAF. "Long-acting prevention, better diagnostics and improved paediatric formulations will not close the gap on their own. A mother who is never tested has not been failed by science, she has been failed by service delivery, or the lack of it."

The session provided further evidence of where systems and services are failing to support women.

Globally, around 95% of pregnant women living with HIV are reached by antenatal care and around 84% are started on antiretroviral therapy. By delivery, 72% are virally suppressed, but retention after birth falls to around 60%.

"Behind every baby who acquires HIV is a mother the system has missed," said Dr Friday Saidi of UNC Project Malawi. "The shortfalls can look small, 5% not reached by antenatal care and around 16% not started on treatment, but the majority of new infections in children in 2025 were in the children of mothers who received no antiretroviral therapy during pregnancy or breastfeeding."

Saidi's account of why women are diagnosed late closely tracked the Ugandan findings. In Malawi, he said, most pregnant women attend antenatal care, and most are tested at their first visit. But women who test negative at that visit are usually not tested again during pregnancy, leaving new cases undetected. In some cases, HIV is only detected when the infant becomes ill, and a clinician begins investigating.

For HIV-negative pregnant women, long-acting pre-exposure prophylaxis is changing how HIV prevention is approached, he said, with the shift from oral PrEP to the vaginal ring, then to two-monthly injectable cabotegravir and now six-monthly lenacapavir. Based on the data he presented, women who acquire HIV during pregnancy account for around a quarter of HIV in infants, meaning that offering PrEP to every eligible woman could avert around a quarter of acquisitions.

Where PrEP has been offered, uptake and satisfaction have been high. However, continuation after childbirth remains a challenge, alongside a lack of partner support and recurrent stockouts despite high demand. Adding prevention options also adds complexity, Saidi said, making it important for health systems to keep pace.

"Ending pediatric HIV requires strong foundations, not only innovation. Let's diagnose our pregnant women early, start those that need treatment early, and also give those that need prevention options as soon as possible."