Dr. Paul Sax from Brigham and Women's Hospital in Harvard Medical School about the top stories in HIV medicine for 2010.
Without a doubt, the top story is going to be progress in HIV prevention. There were 3 major advances:
The first was the CAPRISA [Centre for the AIDS Programme of Research in South Africa] vaginal microbicide study, which showed a 40% reduction for women who use vaginal tenofovir gel compared with placebo, conducted in South Africa.
The second study was the recently published iPrEx [Preexposure Prophylaxis Initiative] study, which demonstrated about the same protection rate in a very different patient population of men who had sex with men (MSM) using [oral] tenofovir/emtricitabine, pre-exposure prophylaxis, giving us the first ever efficacy trial.
The third was the increasing data on treatment as prevention, meaning that the HIV-infected person on treatment is far less likely to transmit the virus to others and so in a subanalysis of a study looking at herpes simplex virus (HSV) treatment for prevention of HIV transmission, they found that there was a 92% reduction in the likelihood of transmission of HIV if the person in the study was on HIV therapy.
Interestingly, the HSV part didn't work. This last part, treatment as prevention, has already, apparently, had an impact in certain communities on the number of new infections and data were published on that phenomenon occurring in Vancouver, as well as in San Francisco.
The good news is that UNAIDS [Joint United Nations Progamme on HIV/AIDS] released data that the number of new infections has actually dropped and they see a turn of the epidemic, in particular, in the places that were hardest hit, such as Sub-Saharan Africa.
This is clearly good news, but on the other side of the coin is the fact that, there are still data from epidemiologic studies showing that we really need these prevention efforts. About 2,000,000 to 3,000,000 people still get infected with HIV yearly and the epidemic continues to be rampant in MSM and in injection drug users. In the United States, about 20% of MSM have HIV infection, and the rates are highest among people of color, and still about 40% of people who tested positive in this study didn't know they were HIV positive.
There is a tremendous need for these prevention efforts and if one wants to link it back to the importance of testing as a way of reducing the number of new infections, a very interesting study on testing practices in the United States showed that more people in the United States are aware of their HIV status than ever before, but that interestingly, still about one third of the people who get tested, are tested at the same time that they already have either diagnosis of AIDS, clinically, or severe HIV-related immunosuppression by the CD4 count. 
1. Karim Q.A., Karim S.S.A., Frolich J.A., et al, on behalf of the CAPRISA 004 Trial Group. Effectiveness and safety of tenofovir gel, an antiretroviral microbicide, for the prevention of HIV infection in women. Science. 2010;329:1168-1174.
2. Grant R.M., Lama J.R., Anderson P.L., et al, for the iPrEx Study Team. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. N. Engl. J. Med. 2010 Nov 23. [Epub ahead of print]
3. Donnell D., Baeten J.M., Kiarie J., et al, for the Partners in Prevention HSV/HIV Transmission Study Team. Heterosexual HIV-1 transmission after initiation of antiretroviral therapy: A prospective cohort analysis. Lancet. 2010;375:2092-2098.
4. Montaner J.S., Lima V.D., Barrios R., et al. Association of highly active antiretroviral therapy coverage, population viral load, and yearly new HIV diagnoses in British Columbia, Canada: a population-based study. Lancet. 2010;376:532-539.
5. Das M., Chu P.L., Santos G-M, Scheer S., Vittinghoff E., et al. Decreases in community viral load are accompanied by reductions in new HIV infections in San Francisco. PLoS ONE. 2010;5:e11068.
6. UNAIDS Report on the Global AIDS epidemic 2010. Available at: http://allafrica.com/download/resource/main/main/idatcs/00020355:772ab65e46c27f0ec5701d2a76d27d84.pdf Accessed December 6, 2010.
7. Vital Signs: HIV testing and diagnosis among adults -- United States, 2001-2009. MMWR. 2010;59;1550-1555. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5947a3.htm?s_cid=mm5947a3_w, Accessed December 6, 2010.
8. Prevalence and awareness of HIV infection among men who have sex with men --- 21 cities, United States, 2008. MMWR. 2010;59:1201-1207. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5937a2.htm, Accessed December 6, 2010.