November 30, 2012
Human immunodeficiency virus (HIV) infections attributed to male-to-male sexual contact comprised 64% of the estimated new HIV infections in the United States in 2009.1 Assessing the geographic distribution of HIV infection by transmission category can help public health programs target prevention resources to men who have sex with men (MSM) in areas where HIV infection from male-to-male sexual contact is most frequent. In 2004, CDC published data on acquired immunodeficiency syndrome diagnoses among MSM and others by metropolitan statistical area (MSA).2 To examine geographic differences in the prevalence of HIV infection from male-to-male sexual contact among persons aged ≥13 years in the United States and Puerto Rico, CDC estimated the number of HIV infections in persons newly diagnosed in 2010 and analyzed them by transmission category and location. Results indicated that HIV infections attributed to male-to-male sexual contact made up the largest percentage of HIV infections in MSAs (62.1%), smaller metropolitan areas (56.1%), and nonmetropolitan areas (53.7%). Of the 28,851 infections attributed to male-to-male sexual contact, 23,559 (81.7%) were in MSAs, and 11,410 (48.4%) of those infections were in seven MSAs that represented 31.7% (53,169,004 of 167,919,694) of the overall population aged ≥13 years in the MSAs that were assessed. These data support planning for targeted interventions to prevent HIV acquisition and transmission by male-to-male sexual contact among MSM, particularly in those areas most affected.
HIV infections in persons newly diagnosed in 2010 that were reported to the National HIV Surveillance System through June 2011 were examined from 564 locations, including 103 MSAs, 263 smaller metropolitan areas, and 198 nonmetropolitan areas in the United States and Puerto Rico.* Reported diagnoses of HIV infection for persons aged ≥13 years were tallied, and numbers of diagnoses overall and by transmission category were estimated. Data were adjusted for reporting delays and missing HIV risk factors but not for underreporting.3,4 Because a substantial proportion of persons with diagnosed HIV infection are reported to CDC without an identified risk factor, multiple imputation methods are used to assign transmission categories to those persons whose diagnoses are reported without a risk factor.4 Multiple imputation is a statistical approach in which missing transmission categories for each person are replaced with plausible values that represent the uncertainty regarding the actual, but missing, values.5
Estimates were calculated for new diagnoses of HIV infection attributed to male-to-male sexual contact, injection-drug use, male-to-male sexual contact and injection-drug use, heterosexual contact, and other HIV risk factors or modes of transmission (e.g., hemophilia, blood transfusion, or perinatal exposure). Transmission categories are assigned, based on the single risk factor (of all identified risk factors) that was most likely responsible for HIV transmission.6,7 An exception is male-to-male sexual contact and injection-drug use, which makes up a separate transmission category. Estimates were not calculated for locations that did not have confidential name-based HIV reporting in place by January 2007 (or had not reported these data to CDC since at least June 2007) to enable the calculation of reporting delays. Excluded were locations in Hawaii, Maryland, Massachusetts, Vermont, and the District of Columbia.6
Of the estimated 37,934 persons aged ≥13 years with a diagnosis of HIV infection who resided in MSAs in the United States and Puerto Rico during 2010, a total of 23,559 (62.1%) had HIV infection attributed to male-to-male sexual contact; 10,128 (26.7%) had HIV infection attributed to heterosexual contact, 3,070 (8.1%) to injection-drug use, 1,145 (3.0%) to male-to-male sexual contact and injection-drug use, and 33 (0.1%) to other modes of transmission (Table 1). Among smaller metropolitan areas, 3,182 (56.1%) of 5,677 HIV infections were attributed to male-to-male sexual contact, and among nonmetropolitan areas, 1,756 (53.7%) of 3,272 HIV infections were attributed to male-to-male sexual contact (Table 1). Of the 28,851 HIV infections among persons with infection attributed to male-to-male sexual contact overall, 23,559 (81.7%) were among persons living in MSAs. Persons aged ≥13 years living in MSAs comprised 65.5% (167,919,694 of 256,388,562) of the total population† of persons aged ≥13 years for the areas that were assessed (103 MSAs, 263 smaller metropolitan areas, and 198 nonmetropolitan areas).
A total of 11,410 (48.4%) of the 23,559 estimated HIV infections attributed to male-to-male sexual contact were among persons who resided in seven MSAs: New York, New York, New Jersey, Pennsylvania (3,347); Los Angeles, California (2,589); Miami, Florida (1,481); Atlanta-Sandy Springs-Marietta, Georgia (1,059); Chicago, Illinois, Indiana, Wisconsin (1,011); Dallas, Texas (995), and Houston-Baytown-Sugar Land, Texas (928) (Table 2). Persons aged ≥13 years residing in these seven MSAs comprised 31.7% (53,169,004 of 167,919,694) of the total population of persons aged ≥13 years for the MSAs that were assessed. The four largest percentages of HIV infections attributed to male-to-male sexual contact in MSAs were in Los Angeles, California (81.9%), Fresno, California (80.8%), Modesto, California (78.8%), and Oxnard-Thousand Oaks-Ventura, California (78.2%).§
Reported by: Hollie Clark, M.P.H., H. Irene Hall, Ph.D., Tian Tang, M.S., Shericka Harris, M.P.H., Anna Satcher Johnson, M.P.H., Joseph Prejean, Ph.D., Div of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC. Corresponding contributor: Hollie Clark, email@example.com, 404-639-3983.
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