A fundraising concert will take place in South Africa later today featuring Bono and Beyonce, to mark of AIDS awareness day on Monday.
At home, third world development group Dóchas and the Dublin AIDS alliance are launching their campaign to raise funds for AIDS charities.
A giant red ribbon is being pinned to the gates of St Stephen's Green and volunteers are selling ribbons to members of the public.
The South African concert has been organised by the Nelson Madela Foundation to raise awareness of the deadly virus blighting millions of lives around the world.
The former South African president gave Annie Lennox, Bono and other artists a tour yesterday of Robben Island where he spent 18 of his 27 years in jail during the apartheid era.
And he told them defeating Aids would take more effort and unity than defeating apartheid.
“We are called to join the war against HIV/Aids with the same, and even greater, resolve than was shown in the fight against apartheid,” Mr Mandela said.
“We have to mobilise all our people, all sectors of society, all our resources and energy.”
Mr Mandela showed them his old prison cell.
“I’m speechless,” said Annie Lennox, who wore a T-shirt reading “17 million Aids dead”.
“I saw a vision of hell where Mr Mandela and his fellow inmates were kept. To sacrifice his life and still come out to fight Aids, it’s incredible.”
The three-hour concert will be watched by 40,000 fans in Cape Town’s Greenpoint stadium and millions more on the web.
The appeal, which uses Mr Mandela’s former prison number, urges people in 17 countries to call a premium-rate line to hear a celebrity message and songs recorded by top artists that have not yet been released.
The whole concert can be seen live and free around the world through the campaign’s website, www.46664.com – Mr Mandela’s prison number.
It will be the world’s largest ever charity web event, according to its organisers.
The concert, titled 46664 – Give one minute of your life to AIDS” will be broadcast from 4.30pm GMT onwards on the web.
It will be shown on TV by Channel 4 and Sky, later in the year.
All proceeds from the event will go to support the work of the Nelson Mandela Foundation in Southern Africa.
Between 34 million and 46 million people around the world are infected with HIV, according to UN figures.
The pandemic killed more than three million people this year.
Some 5.3 million South Africans are HIV-positive – more than in any other country.