Dozens of leading HIV experts were feared killed when a Malaysian plane was shot down over Ukraine, fuelling concerns that research on curing the disease could suffer.
Among them was Joep Lange, who researched the condition for more than 30 years and was considered a giant in the field, admired for his tireless advocacy for access to affordable AIDS drugs for HIV positive patients living in poor countries.
"Global health and the AIDS response have lost one of their great leaders," Peter Piot, director of the London School of Hygiene & Tropical Medicine and a former executive director of UNAIDS, told Reuters in London.
"Joep Lange was one of the most creative AIDS researchers, a humanist, and tireless organizer, dedicated to his patients and to defeating AIDS in the poorest countries."
The United Nations AIDS program, UNAIDS, said it feared "some of the finest academics, health-care workers and activists in the AIDS response may have perished" on the plane.
"Professor Lange was a leading light in the field since the early days of HIV and worked unceasingly to widen access to antiretroviral medicines around the world," it said.
As many as 100 people heading to the AIDS 2014 conference in Melbourne were on the doomed flight, Fairfax Media reported, including Lange, a former president of the International AIDS Society (IAS) which organizes the event.
"The UNAIDS family is in deep shock..."The deaths of so many committed people working against HIV will be a great loss for the AIDS response," said Michel Sidibé, executive director of UNAIDS.
The conference, due to start on Sunday, features former US President Bill Clinton among its keynote speakers and is expecting around 12,000 participants.
The IAS said it was still working with authorities to confirm the number of delegates on the flight and would go ahead with the conference as planned.
