Background US national data suggest that new HIV diagnoses are now declining. However, that decline has been uneven, and has not clearly included men who have sex with men (MSM), the group most affected by HIV in the US.

Methods We used data from the US Census, American Community Survey, and the King County, WA HIV/AIDS Reporting System (NHSS) 2004–2013 to assess trends in the rates of new HIV diagnoses, AIDS diagnoses and age- and reporting lag-adjusted HIV-associated mortality rates among King County residents. Trends in viral suppression, defined as the proportion of individuals with a last reported plasma viral load (VL) result of <200 copies, and CD4 counts were evaluated between 2006 and 2013, the period during which all VL and CD4 results were reportable in WA State. We assessed trends using Chi-square testing.

Results Between 2004 and 2013, the rate of new HIV diagnoses decreased from 18.4 to 13.2 per 100,000 residents (decline of 28%); AIDS diagnosis rates declined 42% from 12.3 to 7.2 per 100,000; and death rates decreased from 27 to 15 per 1,000 persons living with HIV/AIDS (PLWHA) (decline of 44%; p < 0.001 for all three trends). The rate of new HIV diagnoses declined 19% among MSM (p = 0.01), with the largest absolute decline occurring in Black MSM (44%). Among 8,679 individuals with laboratory results reported to NHSS 2006 through 2013, viral suppression increased from 45% to 86% (p < 0.001).

Conclusions The rates of new HIV diagnosis, AIDS diagnoses and mortality in PLWHA in King County, WA have significantly declined over the last decade. These changes have occurred concurrent with a dramatic increase in HIV viral suppression, and have affected diverse populations, including MSM and African American MSM.