For more than three decades, AIDS and those fighting it have been locked in a tango, moving sideways, backwards or forwards, but still a cure remains elusive.
The 20th International AIDS Conference, opening in Melbourne, Australia, on Sunday will have plenty of opportunity to mull the strange dance with this complex, deadly disease.
For several years now, the news has been sunny, a tale of declining mortality and fewer infections -- the outcome of gruelling lab work and billions of dollars in health investment.
Among the greatest pharmaceutical inventions of all time, drugs to repress HIV are more and more reaching those in need, and ways are being explored to use them to prevent infection by the AIDS virus, not just treat it.
Added to this is a campaign under way in sub-Saharan Africa to promote male circumcision, which has been found to be remarkably effective in shielding men from sexually-transmitted HIV.
"It is easy to forget where we were 30 years ago -- overcrowded AIDS wards, little funding for and even less understanding of HIV," Michel Sidibe, chief of the UN's specialist programme UNAIDS, told AFP.
"The AIDS epidemic devastated families, communities and had a major impact on countries where the epidemic took hold. But over the last 15 years, there has been remarkable progress and we have moved from despair to hope."
But, true to AIDS' unpredictable tango, the buoyant mood has been jolted by a sharp disappointment.
A path that seemed to lead to the glittering goal of a cure for HIV now seems to point to a dead end.
The hopes had been sparked by an infant in the United States, known anonymously as "the Mississippi Baby," who was born with HIV to an infected, untreated mother.
She was given a strong dose of drugs immediately at birth and the treatment continued for 18 months, when physicians lost track of her.