Overall, 523,121 identified HIV/AIDS cases captured from 2015 to 2018 in the CRS were analyzed, among which 359,812 (68.78%) cases were reported as having been contracted through heterosexual contact (HC). The proportion of people infected through HC increased yearly from 66.25% (2015) to 71.48% (2018) (Figure 1a). Among all heterosexual transmissions, the proportion of CHC decreased from 40.18% (2015) to 37.99% (2018), whereas the proportion of NMNCHC increased from 46.33% (2015) to 49.02% (2018) (Figure 1b). Among the men who reported transmission through nonmarital heterosexual contact, the proportion of the CHC group declined year by year, from 57.05% (2015) to 54.46% (2018), while the proportion of NMNCHC increased from 42.95% (2015) to 45.54% (2018). In the female nonmarital heterosexual group, the proportion of the CHC group decreased from 14.85% (2015) to 12.02% (2018), while the NMNCHC proportion was much higher and increased annually from 85.15% (2015) to 87.98% (2018) during the years that the study focused on (Figure 1c). In the CHC group, the proportion of men was quite high and increased yearly from 91.97% (2015) to 93.00% (2018). Correspondingly, the female proportion decreased from 8.03% (2015) to 7.00% (2018). The gender ratios (male: female) were 11.45:1, 12.08:1, 12.53:1, and 13.28:1 from 2015 to 2018, respectively. In the NMNCHC group on the other hand, the gender proportion was relatively stable, with males accounting for 60.06% to 60.27%, and the gender ratios (male: female) being 1.50:1, 1.51:1, 1.54:1, and 1.52:1 from 2015 to 2018, respectively (Figure 1d).
During the years analyzed in this study, the average age of the two groups increased annually. The average age of the CHC group increased from 48.32 (2015) to 52.69 (2018), and the average age of the NMNCHC group increased from 42.69 (2015) to 45.23 (2018). Meanwhile, the married proportion of the CHC group was relatively stable, ranging from 51.20% in 2015 to 51.48% in 2018, while the married proportion of the NMNCHC increased from 49.10% in 2015 to 51.02% in 2018. The proportion of divorced or widowed individuals increased annually, while the percentage of those who were unmarried decreased in both groups. The educational level in the CHC group changed during the study years; the proportion of those having graduated junior high school and above decreased annually, while the proportion of those only having graduated primary school as well as those who were illiterate increased annually. The NMNCHC group followed a similar trend, except that the proportion of individuals educated in college or above was comparatively stable, only reducing by 0.68% (from 10.10% in 2015 to 9.52% in 2018), compared with a 2.05% (from 7.39% in 2015 to 5.34% in 2018) decline in the CHC group (Table 1).
During the period in question, the frequency of transmission in the NMNCHC group was higher than that of the CHC group in all age groups under 55 years old, especially in the age group from 20 to 40. However, there was an obvious difference in the age group over 60, in which the number of transmissions in the NMNCHC group was much lower than that of the CHC group. This difference peaked in the age group over 65, in which the frequency of identified PLWHA in the CHC group was 1.52 to 1.59 times that of the NMNCHC group. In the 65+ age group, the CHC group showed a substantial increase, and the proportion of cases identified in the over 65 years in the CHC group increased from 17.92% (2015) to 25.71% (2018), while that in the NMNCHC group increased from 10.24% (2015) to 13.06% (2018) (Figure 2a).
In the CHC group, the 60 to 64 as well as 65 and above age groups had much higher sex ratios (male: female) than the total ratios, which were 15.34:1 (2015), 14.94:1 (2016), 18.06:1 (2017), and 16.64:1 (2018) in the 60 to 64 age group and 37.80:1 (2015), 38.33:1 (2016), 40.12:1 (2017), and 34.16:1 (2018) in the 65 and above age group. Under the age of 40, most age groups of CHC showed a downward trend, but after age 40, there was an increase that peaked at 65+ for both genders. Women made up a small proportion in all age groups, hence the increase in CHC was mainly driven by men in the older age groups (Figure 2b, Figure 2c). On the other hand, in the NMNCHC group, among the age group of 65~, the sex ratios (male: female) were 2.87:1 (2015), 2.71:1 (2016), 2.61:1 (2017), and 2.28:1 (2018). The sex ratio remained relatively stable in all age groups in the NMNCHC; however, there was an obvious increase in the younger age groups, especially in the age group of 25 to 29, which rose from 1.49:1 to 1.91:1 during the years analyzed in this study and became the second highest among all age groups in 2018 (Figure 2b, Figure 2c).
There was a significant age difference between PLWHA infected through CHC and those infected through NMNCHC from 2015 to 2018 (P<0.0001). Those who were infected through NMNCHC were significantly younger than those cases transmitted through CHC (P<0.0001), with an average age gap ranging from 5.63 to 7.46 years. The age of male PLWHA in the CHC group was significantly higher than that in the NMNCHC group (P<0.0001), and the mean age difference was 5.46 years (2015) to 7.82 years (2018). In the female group, there was no significant difference in age between the two groups in 2015 (P=0.398). The age among women of the CHC cases was significantly higher than that of NMNCHC from 2016 to 2018 (2016: P < 0.0001, 2017: P=0.029, 2018: P < 0.0001), but the age differences were much smaller than those of men, ranging from only 0.27 (2015) to 1.62 (2018) (Table 2).
Chi-square analysis of gender distribution of PLWHA infected through CHC and NMNCHC showed significant differences, χ2 (2015) =8909.00, P < 0.0001, χ2 (2016) =9941.90, P < 0.0001, χ2 (2017) =11004.00, P < 0.0001, χ2 (2018) =12836.00, P < 0.0001. In the meantime, the Chi-square tests of marital status between the two groups revealed that the distribution of marital status was significantly different between the groups in all years of the study, χ2 (2015) =94.67, P < 0.0001, χ2 (2016) =109.88, P < 0.0001, χ2 (2017) =58.18, P < 0.0001, χ2 (2018) =152.38, P < 0.0001. The distribution trends of CHC and NMNCHC for each year were tested by educational level, and Z(2015)=10.22, P < 0.0001, Z(2016) =17.88, P < 0.0001, Z (2017) =20.78, P < 0.0001, Z (2018) =16.34, P < 0.0001, which indicated that the proportion of NMNCHC increased with the improvement in educational level (Table 3).