Cuba has become the first country to eliminate the transmission of HIV and syphilis from mother to child, according to the World Health Organisation (WHO).

World Health Organisation director-general Margaret Chan said it was one of the "greatest public health achievements possible".

"This is a major victory in our long fight against HIV and sexually transmitted infections, and an important step towards having an AIDS-free generation," Ms Chan said.

The success is due to universal health coverage, improved access to tests and increased attention to maternal care, which health authorities defined as less than 50 cases of mother-to-child transmission of syphilis or HIV per 100,000 live births.

A small number of cases are allowed to persist, despite the certification, because antiretroviral treatment to prevent mother-to-child-transmission of HIV is not 100 per cent effective.

WHO and the Pan American Health Organisation (PAHO) define the milestone as "a reduction of transmission to such a low level that it no longer constitutes a public health problem".

According to a statement from the WHO, health authorities have been working in Cuba since 2010 to "ensure early access to prenatal care, HIV and syphilis testing for both pregnant women and their partners, treatment for women who test positive and their babies, caesarean deliveries and substitution of breastfeeding".

PAHO director Carissa Etienne said universal access and health coverage were feasible and key to success for Cuba.

"Cuba's achievement today provides inspiration for other countries to advance towards elimination of mother-to-child transmission of HIV and syphilis," she said.

Each year, 1.4 million women living with HIV around the world become pregnant.

If left untreated, they have a 15 to 45 percent chance of passing the virus on to their children during pregnancy, labour, delivery or breastfeeding.

But the risk of transmission is just over one per cent if antiretroviral medicines are given to both mothers and children.

The number of children born annually with HIV was 400,000 in 2009. By 2013, the number had decreased to 240,000.

But health authorities said intense effort was needed to meet the global target of less than 40,000 new child infections per year by 2015.

United Nations AIDS agency executive director Michel Sidibe said the milestone showed ending the AIDS epidemic was possible.

"We expect Cuba to be the first of many countries coming forward to seek validation that they have ended their epidemics among children," he said.