Men who have sex with men (MSM) have become a focus of HIV and other sexually transmitted diseases (STD) control in China. Most of MSM who seek causal partners through online dating platforms do not know their sexual partners' real HIV and STDs infection status, which leads to more high risk status, especially for sexual behaviors. Effective Internet-based partner notification is urgently warranted to increase their risk awareness and prevent HIV and STDs transmission. This study developed an app which can help MSM to query recent HIV and other STDs statuses each other from the testing platform in order that they can find a relatively safety sexual partners and reduce risk of HIV infection.

Because most of the recent "Partner Notification" methods are a kind of afterwards remedial measures and will fail to find some of the infected MSM, researchers propose a preventive measures before they meet together. For MSM who are seeking potential sexual partners through Internet, researchers will encourage them to query health status before they decide to meet each other in order to promote their healthy self-responsibility consciousnes including avoiding HIV and other STDs infection, which will form a real ,digital MSM cohort. Researchers designed a pragmatic stepped wedge cluster randomized controlled trial to evaluate the effect of an intervention paradigm that provides HIV, syphilis, hepatitis B, and hepatitis C status partner notification based on the existing HIV and STDs control methods through an mHealth application (app), to reduce HIV and STDs incidences among MSM in China. More than 6000 MSM of 16 districts in Beijing, China will be grouped into four arms, each arm will cover four indepednent districts of Beijing randomly. The four arms will be randomized to sequentially initiate partner notification intervention through the app at 6-month intervals. All participants will be provided informed consent in the app after a full explanation of the protocol design. Researchers expect that the HIV incidence will be significantly lower and the secondary outcomes will also be better after partner notification intervention. The feasible and affordable public health management paradigm will have implications for HIV and STDs prevention and control among MSM and other key populations.

Inclusion criteria:

1. biologically male,
2. had oral or anal sex with men at least once during their lifetime,
3. 15 years of age or older,
4. had no difficulty using a mobile phone,
5. willing to provide their mobile phone numbers to serve as the unique identification numbers of the app's self-query and partner notification functions,
6. willing to use the app's function modules,
7. willing to complete the questionnaire for the research,
8. willing to continuously receive HIV and STDs testing and consulting services provided by the CBO our research setting at,
9. willing to complete the informed consent document.

Exclusion criteria:

1.had serious physical disabilities or mental diseases.

1. Study Protocol,part of study report and data will be published in journals;
2. Researchers can contact the principal investigator(PI:ZhongweiJia) for IPD through email two years after the end of the trial.

Two years after the end of the trial

Data applicants should send email to PI. Real personal basic information (name, unit, title, etc.), detailed description of required data (required variables,etc.), and research plan should be included in the email. Our team will discuss the research proposal and reply as soon as possible

Because partner notification is a kind of behavioral intervention, participants know what intervention they receive. However, we take efforts to reduce the bias caused by the non-blind design. At the beginning of the research, participants, care providers, and researchers who participate in participants management will not know the randomized scheme. The partner notification will be opened to participants sequentially by the predetermined computer program, and does not need care providers and researchers to implement the intervention manually. The care providers and researchers do not know the implementation of partner notification unless the participants tell them whether they can use the function on their own initiative. Even the care providers know that, the operation and results of the HIV and STDs testing will not be affected. At last, the outcomes assessors do not know the randomized scheme in data analysis.