Mobile big data possesses characteristics such as wide coverage, real-time processing, and continuity, allowing for continuous capture of mobility information from the target population. In this study, we used a longitudinal observational design and used mobile big data app technology, specifically structured query language, to gather information on gay dating app users in Shenzhen through the platform as a service (PaaS) and further analyzed the app use patterns, the geographic distribution of app use and HIV testing and counseling (HTC) of the population over a continuous time: from September 2017 to August 2018, leveraging mobile signaling data.

In addition, as the most important traditional festival in China, the Spring Festival (Chinese New Year) is a time for family reunions, cultural celebrations, and various customs. The unique cultural significance makes it an ideal period for examining population mobility as most people travel to their hometowns. Therefore, to better understand the mobility patterns of the app-using men who have sex with men, we analyzed the geographic location changes of the population in Shenzhen before (January 1-31), during (February 1-28), and after (March 1-31) the Spring Festival, and the destination cities where these men who have sex with men traveled during the Spring Festival in 2018.

According to guidelines for HIV prevention interventions among men who have sex with men from the China CDC, the three most frequently used apps among men who have sex with men are Blued (Blued Inc), Jack'd (Online Buddies Inc), and Zank (Zank Group) [32]. Our preliminary survey also found that approximately 97.2% of men who have sex with men in Shenzhen used Blued [12]. Therefore, all users of the target 3 apps (Blued, Jack'd, or Zank) in Shenzhen were recruited as participants, while only those males aged 15 to 69 years were included for further analysis in this study.

The mobile big data collected and the outcomes in this study are included as follows.

The collection and preliminary statistics of the mobile big data were carried out by China Mobile Communications Corporation (CMCC) according to a signed cooperation agreement. The mobile big data on app user, geographic location, and mobile signaling were obtained from the PaaS platform and stored and analyzed using the Hadoop computing framework in the cloud computing environment of CMCC. Preliminary aggregated statistics, such as app user numbers, the geographical distribution of app use and HTC at subdistrict scale across different time periods, and the distribution of destination cities during the Spring Festival in 2018 were exported from the PaaS platform for further statistical analysis. The male population data at the subdistrict level were obtained from the Shenzhen Bureau of Statistics.

The GIS data (GeoJSON format, Geospatial Standard GS {2024} 0650) for the map of China were downloaded from the National Platform for Common Geospatial Information Services. Areas with extremely sparse populations, such as Guangming Farmland and Inner Lingding Island, were excluded from this study and were not displayed on the Map of Shenzhen, as they have minimal impact on the overall distribution and population mobility patterns.

Given that mobile big data can potentially obtain information of all target app users, this study encompassed the entire target population, assuming all gay dating app users are generally men who have sex with men. CMCC counted all users of the 3 target apps (Blued, Jack'd, or Zank) in Shenzhen using unique phone numbers, allowing effective deduplication. Although dual SIM cards enable 2 phone numbers to be used on a single phone, such instances are relatively rare and unlikely to significantly impact the results given the large population size.

Given that only aggregated data was exported from the PaaS platform for further spatial and statistical analysis, no private information was collected, and no informed consent was required. Privacy protection was fully guaranteed. In addition, this research was reviewed and approved by the Medical Ethics Committee of the Shenzhen Center for Disease Control and Prevention (review number R2017010).

This study represents the first longitudinal observational research on the GSN app use, examining its genuine population size, spatiotemporal and behavioral patterns, and mobility through mobile big data in mainland China. This study found Shenzhen has a larger population of men who have sex with men than expected. The geographic distribution of app-using men who have sex with men in Shenzhen exhibited a clustered pattern in central and western Shenzhen, while their HTC uptake was more concentrated in central-eastern Shenzhen. Moreover, both relatively high internal and interprovincial mobility was observed among those app-using men who have sex with men. The findings provided a comprehensive view of the behaviors and dynamics of app-using men who have sex with men, offering valuable insights to inform enhanced prevention and intervention strategies and guide resource allocation. Moreover, our research demonstrates the potential of mobile big data to address critical gaps often overlooked by traditional research methods, providing more accurate, timely, and comprehensive insights into public health and disease prevention.

This study implied a large population of app-using men who have sex with men in Shenzhen from September 2017 to August 2018, surpassing previous estimates [31]. Moreover, the annual estimate of app-user or male ratio (2.58% among males aged 15-69 years) was relatively high in Shenzhen, compared to the daily estimates of Beijing and Shanghai (0.82% and 0.56% among males aged 18-64 years) from a concurrent experimental study [28]. Literature implied that overestimation might exist in economically developed countries characterized by higher urbanization, higher education levels, more in-migrants, and larger working-age populations [34]. Nonetheless, the population of men who have sex with men may have continued to grow along with the growth of the general population in Shenzhen since 2018, underscoring the increasing need for HIV prevention and intervention efforts targeting men who have sex with men in the region.

Our previous surveillance data indicated a rapid increase in app use among men who have sex with men in Shenzhen since 2016, with Blued being the most frequently used app, consistent with findings from previous data in Shenzhen and other cities [12,26]. An internet survey suggested men who have sex with men in southern China used Jack'd more frequently [35]. Founded in 2010, Jack'd has experienced significant growth, particularly among young men who have sex with men, boasting over 5 million users worldwide since 2014 [36]. Notably, nearly half of the app users were aged between 25-34 years, which aligns with other internet surveys [8,14,35]. In Shenzhen, the median age of new infections was 31 years in 2011-2019, with cases younger than 30 years more frequently observed within molecular transmission clusters [37]. Thus, tailored strategies are needed to enhance the effectiveness of HIV prevention initiatives targeting these younger men who have sex with men.

The temporal distribution pattern of app-using men who have sex with men implied that these men who have sex with men tend to use the apps more frequently during work time (daytime) and social time compared to home time. It is reasonable to assume that app users initially seek potential partners through the internet before transitioning to offline social networking if they find a desirable match from the app. During home time, however, it is likely that most users prefer to rest. This finding suggested a clear temporal distinction: a more active search for connections during work and social hours, and a more relaxed, less frequent engagement during home time. Regarding the geographical distribution, app-using men who have sex with men in Shenzhen exhibited spatial clustering in several subdistricts (Futian, Yuehai, Nanhu, Xixiang, Minzhi, and Longhua) at different time periods. Most clusterings occurred in Nanshan District for work time, Futian District for social time, and Baoan District for home time. This study, for the first time, revealed the spatial heterogeneity for gay dating app–using men who have sex with men in Shenzhen, suggesting that these men who have sex with men were unevenly distributed both at the subdistricts and district levels, as well as among the Hukou residents. As app-using men who have sex with men were more likely to have multiple sexual partners, practice receptive roles in anal sex, and use recreational drugs [12]. By recognizing the different contexts in which men who have sex with men engage with dating apps, public health initiatives can be designed to effectively reach this population at the right times and in the right settings. Traditional HIV prevention services (eg, condoms and lubricants distribution) and interventions (eg, antidrug campaigns) should be delivered more precisely to the identified hot spots based on both temporal and geographical distribution.

Meanwhile, compared to the distribution of app-using men who have sex with men, the prevalence of HTC among this population in Shenzhen showed obvious inconsistencies. HTC rates were concentrated in different subdistricts (eg, Cuizhu, Haishan, Xiangmihu, Nanshan, Shatoujiao, and Huangbei), with the highest clustering observed in Luohu, Futian, and Yantian Districts during social and home time. For work time, HTC is also clustered in Nanshan District. These findings implied that men who have sex with men might prefer to seek HTC services in central districts of Shenzhen, which had higher accessibility to health care [38], or choose these areas for convenience after engaging in high-risk sexual behavior during offline dating or gatherings.

Given the disparities in the distribution of app use and HTC service, it is crucial to allocate more HIV-related health care services (eg, HIV testing and counseling) to western Shenzhen, particularly in subdistricts of Baoan District. Furthermore, the mismatched distribution of app use and HTC and the availability of fee HTC service highlighted the need for outreach initiatives that extend beyond traditional health care settings. Implementing mobile clinics or pop-up testing stations in hot spots or underserved areas could help bridge the HIV testing gap.

Although our previous study implied that app-using men who have sex with men were more likely to take HIV tests, the prevalence of lifetime and recent HIV tests in the past year (70.2% and 50.2%) remained significantly below the UNAIDS target [39]. Furthermore, it is reported that the majority (40%) of the app-using men who have sex with men preferred to take HIV tests at CDCs and community-based organizations (eg, 258-RWG) due to stigma and confidential concerns [39]. Besides, traditional offline HTC services are also available at gay social venues, voluntary counseling and testing centers, or clinics, while the uptake of these services has not been optimal. Therefore, it is essential to prioritize location-tailored strategies for expanding HIV testing, particularly in identified geographical hot spots. Concurrently, innovative web-based prevention initiatives targeting app-using men who have sex with men emerged as a promising alternative. For instance, Blued launched an HIV testing campaign in 2015, which recommended the nearest health care facility or testing service for app users [27]. In light of these insights, future strategies could leverage GSN apps and smartphone tools to promote HTC services, ultimately contributing to the achievement of the first UNAIDS “95” goal.

During the 2018 Spring Festival, more than one-third of app-using men who have sex with men left Shenzhen, highlighting the high mobility of this population. A prior study also reported that about one-fourth of the gay dating app-using men who have sex with men lived in Shenzhen for less than 1 year [12]. The distribution of the destination cities for app-using men who have sex with men demonstrated a relatively centralized flow, with greater internal movement within Guangdong province and less interprovincial mobility to neighboring provinces such as Hunan, Jiangxi, Guangxi, and Hubei. Research suggested that immigrants from Jiangxi, Shaanxi, and Hubei provinces were the main sources of the predominant CRF01_AE subtype in Shenzhen [18]. Local statistics also reported that the immigrants in Shenzhen mainly came from Guangdong (35%), followed by Hunan, Sichuan, Guangxi, Hubei, and Jiangxi. A nationwide study further supported these findings, identifying Hunan, Guangxi, Hubei, and Jiangxi Provinces as the main source provinces for migrant men who have sex with men in Guangdong [28]. During the Spring Festival, the most significant changes in the population of men who have sex with men were observed in the Yuehai, Shatou, and Longhua subdistricts. Therefore, it is crucial to strengthen targeted and innovative prevention and intervention efforts in these areas to address the unique challenges faced by migrant men who have sex with men, such as app-based notifications or location-based services, to provide timely and targeted HIV prevention messages and services, particularly during periods of high mobility.

First, the application of mobile internet has developed rapidly in China, especially in the last 5 years, which may have a significant impact on the behavioral characteristics of men who have sex with men, it would be valuable to collect more recent data to examine the evolution of the trend in the future. Second, as the study is based on mobile big data, there may be inherent biases in estimating the true population size. Third, regarding the geographical difference in app use and HTC, limited demographic data prevented us from differentiating the impact of resource availability from user selection bias. Moreover, it is difficult to distinguish male sex workers and noncommercial men who have sex with men, who may exhibit different HIV-related behaviors [40]. Therefore, future studies with more demographic factors (eg, occupation and income) and other socioeconomic determinants, are needed to differentiate selection bias. Finally, although gay dating app users are generally assumed to be men who have sex with men, it is possible that a small number of non–men who have sex with men individuals may also use the app for research purposes or by chance. However, as this group constitutes a negligible portion of the overall population, their presence is unlikely to affect the results significantly and can therefore be disregarded.

Shenzhen has a large population of men who have sex with men using gay dating apps, predominantly aged 15-34 years. The uneven spatiotemporal distribution of app-using men who have sex with men and their HIV testing or counseling, as well as the mismatch between them, emphasizes the need to adapt the traditional venue-based prevention and intervention strategies to the identified hot spots area and the need for outreach initiatives that extend beyond traditional health care settings. Given the relatively high internal and interprovincial mobility of this population, leveraging smartphone-based behavioral monitoring could provide valuable insights for enhanced and innovative prevention and intervention strategies.