About 100 people traveling to a global AIDS conference in Australia were on board the Malaysia Airlines flight that crashed and killed 298 people in eastern Ukraine, reports the Sydney Morning Herald.

The researchers, health workers and activists were on their way to the International AIDS Conference in Melbourne. Among the victims planning to attend was Dutch national Joep Lange, a top AIDS researcher and former International AIDS Society president. Briton Glenn Thomas, a spokesperson for the World Health Organization and a former BBC journalist, was also on flight MH17.

The International AIDS Society expressed sadness over the news that its colleagues were on the Malaysian jetliner.

“At this incredibly sad and sensitive time the IAS stands with our international family and sends condolences to the loved ones of those who have been lost to this tragedy,” the group said in a statement.

Friends and colleagues of those within the AIDS-research community, including UNAIDS executive director Michel Sidibé, also expressed shock and grief over the tragic deaths on Twitter.

While the medical field mourns the lives of those killed, experts like Associate Professor Brian Owler, federal president of the Australian Medical Association, also fear that breakthroughs in HIV/AIDS research will now be stalled.

“The amount of knowledge that these people who died on the plane were carrying with them and the experiences they had developed will have a devastating impact on HIV research,” Owler told TIME.

“The amount of time it takes to get to a stage where you can come up with those ideas cannot be replaced in a short amount of time. So it does set back work for a cure and strategic prevention of HIV/AIDS very significantly,” he said.

— With reporting by Ian Neubauer / Sydney

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