In recent years, the epidemic of HIV/AIDS among young students has been increasing rapidly in China, especially in men who have sex with men (MSM). Although many surveys have been conducted for presenting the characteristics of MSM in young students, the status of AIDS-related knowledge, attitude and practices (KAP), the molecular epidemiological characteristics of HIV-1 and the feature of transmission networks were still largely unknown among people living with HIV/AIDS (PLWH) in young students. In the present study, we combined analysis of genetic, demographic and epidemiological data of HIV-1 among young students in Nanjing, aiming to provide valuable information for taking effective prevention measures against HIV-1 transmission.
1. A total of 155 young students and 425 non-students were recruited at the first follow-up after HIV-1 diagnosis in Nanjing during 10/2015-06/2017. The information of AIDS-related KAP was collected by questionnaires. The data about social demography, AIDS-related KAP, Highly Active Antiretroviral Therapy (HAART) and sexually transmitted diseases (STDs) of 152 male students were analyzed, in order to understand the HIV/AIDS characteristics of MSM in young students.
2. The Pol sequences were acquired after RNA extraction and PCR amplification. A Neighbor-Joining tree was constructed to determine HIV-1 genotypes. The unidentified genotypes were analyzed with Simplot3.5.1 software. HIV-1 Drug resistance mutations were determined using Stanford University HIV Drug Resistance Database tool: HIVdb Program. The epidemiological characteristics of various strains in young students were described by reconstructing the maximum likelihood trees with reference sequences. The geographical origin of each strain in young students was inferred by the Bayesian evolutionary analysis. The changes in the effective population size of the new recombinant strains were explored by the Bayesian skyline plot analysis.
3. The genetic transmission networks of CRF01_AE and CRF07_BC strains were constructed by four steps, including phylogenetic tree construction, transmission cluster extraction, minimum genetic distance identification and network visualization. Cluster Picker was used to extract transmission clusters from the phylogenetic tree, with the node support threshold greater than 95% and intra-cluster maximum pairwise distance less than 3.0% nt substitutions per site. The minimum patristic genetic distance algorithm was used to define the linkages within a cluster. Descriptive analysis was used for exploring the population and geographic origin of HIV-1 in students, and for identifying the characteristics of super-spreaders in the networks. Chi-square test was used to determine the factors that contributed to the networks and super-spreaders.
1. HIV-related KAP of PLWH among male college students. Among PLWH in male college students, 96.1% (146/152) were infected by homosexual behaviors, and 52.6% (80/152) were freshman and sophomore. The overall awareness rate of ‘Eight Items of HIV/AIDS Knowledge’ was 86.2% (131/152), with the awareness rates of item 6 (65.8%, 100/152) and 2 (70.4%, 107/152) lower than those of the other six items. The awareness rates of the infected status towards male regular sexual partners, male casual sexual partners, female regular sexual partners and female casual sexual partners were 16.4% (18/110), 3.0% (3/101), 50.0% (11/22) and 16.7% (2/12), respectively. While having sex with those sexual partners, the proportions of male college students having the awareness that they may be infected with diseases were 20.9% (23/110), 27.7% (28/101), 0.0% (0/22) and 16.7% (2/12), respectively, and the proportions of using condoms insistently were 10.9% (12/110), 11.9% (12/101), 18.2% (4/22) and 33.3% (4/12), respectively. In addition, the proportions of individuals who contact those sexual partners by mobile applications were 84.2% (84/99), 92.6% (88/95), 19.0% (4/21) and 30% (3/10), respectively.
2. The status of diagnosis and treatment of PLWH among male college students. The median CD4+T cell count of the first follow-up after diagnosis was 417.0 (IQR: 319.0-527.0) cells/μL, and 31.5% (47/149) individuals had CD4+T cell count ≥500 cells/μL. The rate of the PLWH having accepted HAART was 69.7% (106/152) until deadline (July 1, 2017). The median of interval time from diagnosis to HAART was 45.5 (IQR: 28.0-130.5) days. For the 46 PLWH who did not start treatment, the median of interval time from diagnosis to deadline was 494.5 (IQR: 275.0-1195.0) days.
3. The distribution of HIV-1 genotypes among young students. A total of 141 Pol sequences among students were amplified successfully. CRF01_AE was the most prevalent strains, accounting for 46.1% (65/141), followed by CRF07_BC (32.6%, 46/141), CRF55_01B (3.5%, 5/141), CRF67_01B (3.5%, 5/141), subtype B (2.1%, 3/141) and CRF68_01B (0.7%, 1/141). In addition, 11.3% (16/141) of sequences were the unidentified genotypes (U). The overall distribution of HIV-1 genotypes among young students was similar to that among non-students.
4. The epidemiological characteristics of HIV-1 among young students. Different HIV-1 strains had various epidemiological characteristics among students. Above 90.0% (60/65) of students were located in four major lineages of CRF01_AE strains, and nearly half of (52.3%, 34/65) students were located in lineage 1, while 71.7% (33/46) of students were dispersed in multiple minor lineages of CRF07_BC strains. In addition, the majority of 16 unidentified genotype U sequences were 01C_like recombinants (81.3%, 13/16), which had formed a distinct cluster spreading rapidly among young students in Nanjing.
5. Characteristics and influencing factors of HIV-1 transmission networks. Of the 65 CRF01_AE sequences, 32 (49.2%) were identified as belonging to 23 separated networks. Of the 46 CRF07_BC sequences, 29 (63.0%) were identified as belonging to 22 separated networks. Lower age while being diagnosed (P=0.041), homosexual behaviors (P=0.020), recent infection (P<0.001) and a lower rate of condom usage (P<0.05) were factors of contributing to network formation.
6. Characteristics and influencing factors of super-spreaders. Of 103 CRF01_AE-infected individuals in student-related networks, 12.6% (13/103) had ≥3 links, but they were involved in 47.6% (49/103) persons through multiple links. Among 13 CRF01_AE-infected super-spreaders, 6 individuals shared links with 6 students respectively. Of 112 CRF07_BC-infected individuals in student-related networks, 8.3% (16/112) had ≥3 links, but they were involved in 51.8% (58/112) persons through multiple links. Among 16 CRF07_BC-infected super-spreaders, 7 individuals shared links with 7 students respectively. Homosexual behaviors (P=0.024), recent infection (P=0.001) and a lower rate of condom usage (P<0.001) were factors associated with super-spreaders.
7. Population and geographical origin of HIV-1 among young students. Of 32 students in CRF01_AE networks, 71.9% (23/32) were infected by non-students, and 18.7% (6/32) were infected by students. Among the 32 CRF01_AE-infected students, half of (50.0%, 16/32) persons had transmission linkage with individuals diagnosed in Nanjing. In addition, 9.4% (3/32) and 25.0% (8/32) of persons had transmission linkage with individuals diagnosed in other cities in Jiangsu province and other provinces, respectively. Of 29 students in CRF07_BC networks, 93.2% (27/29) were infected by non-students, and 3.4% (1/29) were infected by students. Among the 29 CRF07_BC-infected students, 31.0% (9/29) and 6.9% (2/29) persons had transmission linkage with individuals diagnosed in Nanjing and other cities in Jiangsu province, respectively. In addition, 24.1% (7/29) of persons had transmission linkage with individuals diagnosed in other provinces.
1. The age of infecting with HIV-1 becomes younger, thus the AIDS prevention education should be carried early, timely and comprehensively. As the HIV-related KAP of young students is unpromising, it is necessary to strengthen risk warning education to increase AIDS knowledge rate, to enhance the awareness of AIDS prevention and to increase condom usage. In addition, mobile applications, which have been the main tools for the population to contact sexual partners, should be used in programs for HIV prevention and control. Moreover, a high proportion of people who did not have timely diagnosis and treatment indicates that much more attention should be payed to HIV counseling and testing, to popularizing knowledge of HAART and to mobilizing PLWH who have not start treatment to receive HAART as early as possible.
2. Several new recombinant strains including CRF55_01B, CRF67_01B and CRF68_01B are widely epidemic in Nanjing, and have been transmitted into students. In addition, large number of unidentified 01C_like strains spread rapidly in students. Thus, urgent implementation of comprehensive control measures is necessary to monitor and curb the spread of HIV epidemic in young students.
3. The MSM among young students in Nanjing were mainly infected by non-students. The transmission linkage exists not only in the individuals diagnosed in Nanjing (intra-city), but also in the individuals diagnosed in Nanjing and other cities in Jiangsu and other provinces (inter-province). This shows that HIV-1 in young students have complex origins, and also emphasizes that the AIDS prevention in colleges should be taken into the overall consideration in general population.
4. A minority of super-spreaders indeed drive transmission networks to a significant extend. Identification and precision intervention of these individuals are necessary for curbing the spread of HIV-1 among general populations. Homosexual behaviors, recent infection and a lower rate of condom usage are contributing factors of network formation and super-spreaders. Therefore, urgent implementation of comprehensive control measures including curbing the HIV-1 epidemic seriously in MSM, proceeding HIV counseling and testing, promoting accessibility and utilization of condoms should be conducted.