The number of adolescent deaths from AIDS has tripled over the last 15 years, most of the patients having acquired the disease when they were infants, according to new data released on Friday by UNICEF.

AIDS is the number one cause of death among adolescents in Africa and the second leading cause of death among adolescents globally. Among HIV-affected populations, adolescents are the only group for which the mortality figures are not decreasing, according to UNICEF, reported Xinhua.

In sub-Saharan Africa, the region with the highest prevalence, girls are vastly more affected, accounting for 7 in 10 new infections among 15-19 year olds. However, among adolescents in that age group in the region, just over 1 in 10 are tested for HIV, it said.

"It is critical that young people who are HIV-positive have access to treatment, care and support," said Craig McClure, Head of UNICEF's global HIV/AIDS programmes. "At the same time, those who are HIV-negative must have access to the knowledge and means to help them stay that way."

According to the data in UNICEF's Statistical Update on "Children, Adolescents and AIDS", less than half of children under 2 months old are tested for HIV. Only 1 in 3 of the 2.6 million children under the age of 15 living with HIV are on treatment.

The new data states that most adolescents who die of AIDS-related illnesses acquired HIV when they were infants, 10 to 15 years ago, when fewer pregnant women and mothers living with HIV received anti-retroviral medicines to prevent HIV transmission from mother to child.

However, since 2000, nearly 1.3 million new infections among children have been averted, largely due to advances in the prevention of mother-to-child transmission of HIV.

By 2014, 3 in 5 pregnant women living with HIV received anti-retroviral treatment to prevent transmission of the virus to their babies. This has translated into a 60% reduction in AIDS-related deaths among children under 4 years of age since 2000, according to the UNICEF.

The data reveal that currently among adolescents (15-19): 26 new infections occur every hour; and about half of those living with HIV are in just six countries: South Africa, Nigeria, Kenya, India, Mozambique and Tanzania.