The Miami-Dade County medical examiner's department says Montreal HIV/AIDS researcher Dr. Mark Wainberg died of an asthma attack that he suffered while swimming on Tuesday afternoon in Bal Harbour, Fla.

The medical examiner's department released the cause of death Thursday, listing it as "acute asthma exacerbation" which caused the 71-year-old doctor to be submersed.

Wainberg's death has been ruled accidental.

Bal Harbour police said Wainberg's son swam out to his father and pulled him onto the beach, where he was when authorities arrived. Wainberg was later pronounced dead in hospital.

A leader in the fight against AIDS, Wainberg was, at the time of his death, lead investigator at the Lady Davis Institute for Medical Research at the Jewish General Hospital and director of the McGill University AIDS Centre.

A trailblazer in HIV/AIDS research, Wainberg was internationally recognized for his role in the discovery in 1989 of 3TC or Lamivudine, an anti-viral drug which is used in combination with other medications to treat infections caused by HIV.

'He was not afraid to talk truth to power'

Wainberg's sudden death has prompted an outpouring of grief from within the scientific community and also from those he helped.

Ken Monteith, the executive-director of Quebec's network of AIDS organizations (COCQ-SIDA), credits Wainberg for saving his life after he was diagnosed with HIV.

"One of medications I've been taking ever since and haven't stopped taking is the one that he participated in developing," said Monteith.

"If it were not for treatment I would not be here today."

Mark Wainberg

Dr. Mark Wainberg, right, was a pioneer in HIV/AIDS research. (CBC)

Dr. Gerald Batist, the current acting director of the Lady Davis Institute, said his former colleague championed his research on the global stage while ensuring 3TC was accessible to those who needed it.

"He said, 'Look, now I have the drug, I have to bring them to people,'" said Batist. "He went to Africa, he confronted social concerns and resistance to helping the gay population and women, so he implemented his treatment."

"This is transformational. He's a man who went from the bench to the bedside, as we always say — but truly."

Ken Monteith

Ken Monteith credits Dr. Mark Wainberg for saving his life. (CBC)

Wainberg served as president of the International AIDS Society from 1998 to 2000. He also helped organize the 13th International Congress on AIDS in Durban, South Africa in 2000 and the 16th congress, in Quebec City, in 2006.

Monteith said the congress in Durban is a testament to how Wainberg was both a scientist and an activist in the field of HIV/AIDS research.

"He was not afraid to stand up to the South African president who was buying into the AIDS denialist position," said Monteith. 

"He was not afraid to talk truth to power."

With files from Jay Turnbull, Salimah Shivji and Sabrina Marandola