Scores of top international AIDS researchers perished among the 298 aboard Malaysia Airlines Flight MH17, which was downed by missile over Eastern Ukraine Thursday.

As the best efforts of humanity collided with possibly the worst, as many as 100 researchers died while traveling to an international conference in Australia. Among the dead was Joep Lange, a longtime AIDS researcher since 1983 who recently led the Department of Global Health at the University of Amsterdam. Also onboard the flight was World Health Organization spokesman Glenn Raymond Thomas, of Geneva, Switzerland.

Already in Melbourne for the conference, UNAIDS Executive Director Michel Sidibé posted a condolence message on Twitter after the aircraft was shot down by missile over disputed territory in Eastern Ukraine. “My thoughts & prayers to families of those tragically lost on flight #MH17,” he wrote, according to the NY Daily News. “Many passengers were enroute to #AIDS2014 here in #Melbourne.”

The weeklong conference in Melbourne features a number of prominent figures, including former U.S. President Bill Clinton. On Friday, organizers of the conference issued a statement about the tragedy.

“The International AIDS Society (IAS) today expresses its sincere sadness at receiving news that a number of colleagues and friends en route to attend the 20th International AIDS Conference taking place in Melbourne, Australia, were on board the Malaysian Airlines MH17 flight that has crashed over Ukraine earlier today,” the statement read. “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 Boeing 777 left Amsterdam on Thursday on a path toward Kuala Lumpur but was shot down over Ukraine approximately 25 miles from the Russian border. Among the dead were:

Netherlands 154

Malaysia 43 (including 15 crew and 2 infants)

Australia 27

Indonesia 12 (including 1 infant)

United Kingdom 6

Germany 4

Belgium 4

Philippines 3

Canada 1

"Missing" 41 adults

Denis Napthine, premier of Victoria, told The Associated Press that reports were too “immature” yet to release an accurate death toll for researchers headed to the 20th annual AIDS conference. "There's been confirmed a number of senior people who were coming out here who were researchers, who were medical scientists, doctors, people who've been to the forefront of dealing with AIDS across the world," Napthine said at a press conference in Melbourne. "The exact number is not yet known, but there is no doubt it's a substantial number.”

Russia has denied involvement in downing the aircraft, although Ukraine is blaming Russian separatists in the East.