Gery Keszler said the progress achieved in fighting AIDS over the 26 years since the ball's inception meant it had become harder to raise funds to hold the event.

“AIDS has changed from a death sentence to being a chronic disease. The paradox of this success is that the number of allies for AIDS charity projects is decreasing both at home and abroad,” Keszler said in a statement.

Launched by former make-up artist Keszler, among others, and hosted in the prestigious surroundings of Vienna's Town Hall, the ball has raised around 30 million euros ($34 million) for anti-AIDS causes within Austria and abroad, according to organisers.

Rooted firmly in activism among Vienna's LGBT community, the ball grew into a major draw for celebrities, also attracting up to 45,000 spectators a year.

The event often grabbed headlines for the lavish costumes worn by famous guests — 2015's “Holy Spring” theme saw the red carpet teem with paradise birds, angels and Amazonian beauties.

Attendees have run the gamut from the world of politics — such as former US president Bill Clinton — to fashion stalwarts like Vivienne Westwood, Jean Paul Gaultier and Naomi Campbell.

Actors, such as Charlize Theron, Sharon Stone, Sean Penn and Antonio Banderas, have also graced the event alongside music stars, such as Elton John and Austria's own Conchita Wurst.

Eurovision winner Conchita said in a Facebook post that the ball had given her “countless beautiful memories”, adding: “It will always remain close to my heart.” 

However, the amount of money raised has progressively fallen — reaching just 1.3 million euros in 2018 — making it more difficult to justify the resources needed to organise the event.

The 26th and final edition of the ball is set for June 8, with American actress Katie Holmes among those attending.

Holmes is an ambassador for the AmfAR anti-AIDS foundation. Extra tickets will be on sale to cater to an expected rise in demand for the last ball, Keszler said.

“They were incredible, fantastic and intense years,” Keszler said, reflecting on the event's history.

“We achieved more than we ever dared hope. I am so eternally grateful,” he said, adding: “It is now time to bring this project to a fitting conclusion.”

He said that the Life+ association, which is responsible for putting the ball on, would continue to combat anti-AIDS stigma and discrimination.

Some of the previous beneficiaries of funds raised by the ball expressed their concerns over the impact of it ending.

The Aids Hilfe Wien association said it feared losing up to 200,000 euros a year which it uses to help HIV patients access treatment.

“We don't know how we will replace these funds,” association president Wolfgang Wilhelm told the APA agency.

Nevertheless Wilhelm thanked Keszler for what he called his “marathon-like efforts” over the years. 

“It has made an incalculable contribution to raising awareness as well as funds,” he said.

AIDS, or the Acquired Immunodeficiency Syndrome, is the most advanced stage of infection with the Human Immunodeficiency Virus (HIV), which targets the immune system.

The World Health Organization estimated around 36.9 million people were living with HIV at the end of 2017, with 1.8 million people newly infected that year and 940,000 HIV-related deaths.