title: Using a geolocation social networking application to calculate the population density of sex-seeking gay men for research and prevention services.
abstract: BACKGROUND
  In the United States, human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) continues to have a heavy impact on men who have sex with men (MSM). Among MSM, black men under the age of 30 are at the most risk for being diagnosed with HIV. The US National HIV/AIDS strategy recommends intensifying efforts in communities that are most heavily impacted; to do so requires new methods for identifying and targeting prevention resources to young MSM, especially young MSM of color.
  
  
  OBJECTIVE
  We piloted a methodology for using the geolocation features of social and sexual networking applications as a novel approach to calculating the local population density of sex-seeking MSM and to use self-reported age and race from profile postings to highlight areas with a high density of minority and young minority MSM in Atlanta, Georgia.
  
  
  METHODS
  We collected data from a geographically systematic sample of points in Atlanta. We used a sexual network mobile phone app and collected application profile data, including age, race, and distance from each point, for either the 50 closest users or for all users within a 2-mile radius of sampled points. From these data, we developed estimates of the spatial density of application users in the entire city, stratified by race. We then compared the ratios and differences between the spatial densities of black and white users and developed an indicator of areas with the highest density of users of each race.
  
  
  RESULTS
  We collected data from 2666 profiles at 79 sampled points covering 883 square miles; overlapping circles of data included the entire 132.4 square miles in Atlanta. Of the 2666 men whose profiles were observed, 1563 (58.63%) were white, 810 (30.38%) were black, 146 (5.48%) were another race, and 147 (5.51%) did not report a race in their profile. The mean age was 31.5 years, with 591 (22.17%) between the ages of 18-25, and 496 (18.60%) between the ages of 26-30. The mean spatial density of observed profiles was 33 per square mile, but the distribution of profiles observed across the 79 sampled points was highly skewed (median 17, range 1-208). Ratio, difference, and distribution outlier measures all provided similar information, highlighting areas with higher densities of minority and young minority MSM.
  
  
  CONCLUSIONS
  Using a limited number of sampled points, we developed a geospatial density map of MSM using a social-networking sex-seeking app. This approach provides a simple method to describe the density of specific MSM subpopulations (users of a particular app) for future HIV behavioral surveillance and allow targeting of prevention resources such as HIV testing to populations and areas of highest need.
authors.affiliation: Department of Epidemiology, Laney Graduate School, Emory University, Atlanta, GA, United States. kpdelan@emory.edu.
authors.forename: Kevin P
authors.identifier: http://orcid.org/0000-0002-7562-7647
authors.initials: KP
authors.lastname: Delaney
authors.forename: Michael R
authors.identifier: http://orcid.org/0000-0002-6372-6170
authors.initials: MR
authors.lastname: Kramer
authors.forename: Lance A
authors.identifier: http://orcid.org/0000-0001-5002-8886
authors.initials: LA
authors.lastname: Waller
authors.forename: W Dana
authors.identifier: http://orcid.org/0000-0003-4069-3262
authors.initials: WD
authors.lastname: Flanders
authors.forename: Patrick S
authors.identifier: http://orcid.org/0000-0002-7728-0587
authors.initials: PS
authors.lastname: Sullivan
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American; D035843:Biomedical Research; D040362:Geographic Information Systems; D005845:Georgia; D015658:HIV Infections / Q000517:prevention & control; D018451:Homosexuality, Male / Q000208:ethnology / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008913:Minority Groups / Q000706:statistics & numerical data; D063731:Mobile Applications; D011156:Population Density; D012725:Sexual Behavior; D061108:Social Media; D060756:Social Networking; D044465:White People; D055815:Young Adult
keywords: HIV; Internet; MSM; sampling, location services