By Agence France-Presse
The pontiff also issued a fresh call for every sufferer, no matter how poor, to have access to treatment.
In a message ahead of World Aids Day on Thursday the Argentinian pontiff said millions were living with the disease and "only half of them have access to lifesaving treatment".
He added: "I ask you to pray for them and their loved ones and promote solidarity so that even the poorest can benefit from diagnosis and adequate treatment.
"And finally I call on everyone to adopt responsible behaviour to prevent the further spread of this disease."
Francis's comments are likely to be interpreted as a fresh signal of the Church's easing of its opposition to the use of condoms in response to Aids.
His predecessor Benedict XVI said in 2010 that it was acceptable to use prophylactics if the sole intention was to reduce the risk of Aids infection.
Francis's comments could however also be seen as a call for carriers of the HIV virus, that can lead to Aids, to refrain from having sex.
He has previously said that the issue poses a "perplexing" question for Church teaching, which maintains that contraception interferes with the creation of life, and should therefore be forbidden. Benedict acknowledged that this position was problematic if contraception was being used to avoid the risk of death.