Previous discoveries include how male circumcision can reduce by almost 65 percent the risk of transmitting the human immunodeficiency virus, the effectiveness of vaginal microbicides and drug treatments that can prevent an infected pregnant mother from passing the disease to her child.
More recently, two clinical trials have shown just how effective antiretroviral drugs can be in preventing the spread of the incurable disease.
A study that ran from 2007-2009 and was published late last year showed that a combination of these drugs taken orally by uninfected gay men lowered their risk by 44 percent of becoming infected.
That rate rose above 70 percent when the pills were taken regularly, said Fauci who added he has "been in it now literally every day of my life for the last 30 years."
A clinical trial released this month involving mainly heterosexual couples in which one was infected and one was not showed a near elimination of the risk of transmission when the infected partner began an early regimen of antiretrovirals.
This trial is "extremely important because it proves the concept that when you seek out and treat them early rather than wait for their disease to advance, you have not only the well known beneficial effect of being good for the individual patient, but you have a very powerful secondary effect of preventing the transmission from the infected partner to their healthy sexual partner," said Fauci.
The NIAID and its researchers have been at the forefront of the fight against AIDS since the epidemic first surfaced in June 1981.
With regard to the hunt for a reliable vaccine, researchers have found some hope after 20 years of failure in a 2009 clinical trial carried out in Thailand.
"The vaccine trial in Thailand was only 31% effective. However that is at least a proof of concept that we can do better."
In 2010, teams of researchers identified two antibodies in a single individual which when combined in the lab blocked 90 percent of HIV strains known in the world.
Now that research is honing in on what specific part of the virus should be isolated for a vaccine.
"So if we are going to have a vaccine this year or next year or the year after, we don't know, but we are certainly making considerable progress."
In the meantime, a more comprehensive use of existing methods for prevention must be applied in the developing world in order to put the brakes on the epidemic, Fauci said.
"In the low and middle income countries, we only have about 30 to 40 percent of the people who really need therapy getting access to therapy," he said.
"The only way we can address this -- and this is the focus of what is going on over the past couple of years -- is prevention of HIV infection."
There are 2.7 million new infections each year, he added.
This gap will be difficult to bridge, warned Fauci, especially since the global economic turndown has slashed research budgets as a time when scientists need $10 to 15 billion (seven to 10 billion euros) more per year than the total 11 billion currently available for research.
"Unfortunately there is a very difficult constraint on resources throughout the world," he said.