Dr. Gallo is recognized internationally for his co-discovery of HIV as the cause of AIDS. As a biomedical research scientist, he since has spent much of his career working to eliminate AIDS and other viral chronic diseases. In the early 1980s, Gallo and his team also pioneered the development of the HIV blood test, which enabled healthcare labors to screen for the AIDS virus for the first time, leading to a more rapid diagnosis while simultaneously protecting patients receiving blood transfusions. His research also helped physicians develop HIV therapies to prolong the lives of those infected with the virus. His 1996 discovery that a natural compound known as chemokines can block the HIV virus and halt the progression of AIDS was hailed by Science magazine as one of that year's most important scientific breakthroughs.

Before the AIDS epidemic, Gallo was the first to identify a human retrovirus and the only known human leukemia virus—HTLV—one of few known viruses shown to cause a human cancer. In 1976, he and his colleagues discovered Interleukin-2, which is a growth-regulating substance now used as therapy in some cancers and even AIDS. Then in 1986, he and his group discovered the first new human herpes virus in more than 25 years (HHV-6), which was later shown to cause an infantile disease known as Roseola.

Today, Dr. Gallo's work continues at the Institute of Human Virology (IHV), an institute of the University of Maryland School of Medicine that Dr. Gallo helped found in 1996. IHV is the first virology center of its kind, combining the disciplines of research, patient care and prevention programs in a concerted effort to speed the pace of progress. In 2011, Gallo co-founded the Global Virus Network to position the world to rapidly respond to new or re-emerging viruses that threaten mankind, to achieve collaboration among the world’s leading virologists, and to support next-generation training.

Prior to becoming IHV director in 1996, Gallo spent 30 years at the National Institutes of Health's National Cancer Institute, where he was head of its Laboratory of Tumor Cell Biology. Dr. Gallo has received numerous scientific honors and awards from around the world, holds 35 honorary doctorates, and has published nearly 1,200 papers.

Dr. Gallo was the most referenced scientist in the world in the 1980s and 1990s, during which time he had the unique distinction of twice winning America’s most prestigious scientific award—the Albert Lasker Award in Medicine - in 1982 and 1986. He was ranked third in the world for scientific impact for the period 1983-2002 (PNAS, November 15, 2005, vol102, no.46, 6569-16572).
Gairdner Foundation International Award (Canada), 1987