The International AIDS Conference will be held in the US for the first time after San Francisco hosted the event in 1990, thanks to Barbara Lee, an Oakland Democrat, who insisted on ending a US ban on travellers carrying the HIV virus.
Her bill became law under president George W Bush in 2008 as part of a landmark effort to combat AIDS worldwide, known as the President's Emergency Plan for AIDS Relief. It came into effect on 4 January 2010, under president Obama.
The conference, to open tomorrow, in Washington, is expected to draw 20,000 people, including medical pioneers who confronted the disease in the 1980s in San Francisco, which was its epicentre at the time.
The travel ban was clamped in 1987, with the Department of Health and Human Services adding HIV to the list of communicable diseases that banned a person from entering the US.
Lee said the ban had been in place for years, and she considered it unjust and discriminatory, but since it had not been lifted, and so no one believed it could be.
The ban was controversial when Lee set out to get it lifted, related as it was to immigration and with George W Bush, a republican as president.