Demographic features of identified PLWHA infected through commercial and nonmarital noncommercial heterosexual contact in China from 2015 to 2018: a retrospective cross-sectional study

In China, sexual transmission has already become the predominant route of human immunodeficiency virus (HIV) infection [1]. In 2013, 90.8% of newly identified HIV infections and acquired immune deficiency syndrome (AIDS) cases were reported to have been transmitted through sexual contact, among which heterosexual transmission accounted for 69.4% of the total cases [2]. During the following years, newly reported people living with HIV/AIDS (PLWHA) infected through heterosexual contact made up approximately two-thirds of the total number of cases [3, 4]. According to the report of the National AIDS and STD Epidemic in the third quarter of 2018, 29,416 cases of newly identified HIV/AIDS cases in China were transmitted through heterosexual contact, accounting for 71.1% of the total [5].

Heterosexual transmission can be broadly divided into three types: those acquired within marriage or another type of live-in partnership, those acquired when selling or buying sex and those acquired in sex with a casual partner, including transient girlfriends and boyfriends [6]. Previous studies of heterosexual transmission have mainly focused on commercial heterosexual transmission and transmission within marriage [7, 8], and there are few studies that subdivided the modes of heterosexual transmission and conducted a synthesized analysis. To distinguish among different types of heterosexual contact, the option of a contact history, including commercial or noncommercial heterosexual contact, was added as a subclassification of nonmarital heterosexual transmission in the Chinese HIV/AIDS Case Reporting System (CRS) in 2014. Based on this, we were able to analyze the characteristics of PLWHA transmitted through commercial heterosexual contact (CHC) or nonmarital noncommercial heterosexual contact (NMNCHC).

Both CHC and NMNCHC are important components of heterosexual transmission. CHC plays a significant role in HIV transmission [9, 10], and female sex workers (FSWs) and male clients of FSWs are among the key populations monitored by the National Sentinel Surveillance System [11]. In 2015, the overall HIV positive rate of FSWs was 0.19%, while the rates were 0.39, 0.10 and 0.07% among FSWs from low-, medium- and high-level venues, respectively [12]. Despite a seemingly low HIV prevalence among FSWs in China, the scale and risk of HIV infection is enormous given the size of the population of FSWs and their clients [13]. Many studies have shown that the male clients of FSWs are important bridges for HIV transmission from FSWs to the low-risk general population [14‐18]. In addition, several regional studies with comparatively small sample sizes noticed that NMNCHC accounted for an increasingly high proportion of nonmarital heterosexual transmission [19‐24]. However, piecemeal data cannot provide a broad picture of nationwide epidemics. In the meantime, the concealment and diversity of NMNCHC made it difficult to understand its characteristics and significantly increased the difficulty of controlling the spread of HIV [22].

Since different transmission routes have varied characteristics and risk factors, the HIV/AIDS prevention and control strategies for heterosexual transmission should be formulated and carried out according to the different heterosexual transmission modes [25, 26]. Understanding the characteristics of cases infected through CHC and NMNCHC is important for HIV/AIDS prevention work in China. However, there is a lack of national-level analysis on the epidemic characteristics of those two transmission routes. Due to these considerations, this study applied the CRS data from 2015 to 2018 to synthetically describe and preliminarily compare the demographics of NMNCHC and CHC.

To our knowledge, this is the first study to analyze and compare the basic demographic characteristics of PLWHA reported as transmitted through CHC and NMNCHC at the national level. By analyzing data from the Chinese HIV/AIDS CRS from 2015 to 2018, we have gained a preliminary understanding of the demographics and differences between CHC and NMNCHC. This study provides further indications that heterosexual contact has become the main mode of HIV transmission in China. Furthermore, the proportion of NMNCHC in heterosexual transmission increases annually, indicating that NMNCHC is playing an increasingly important role. These findings support the conclusions of some small regional studies at the national level [22‐24].

In nonmarital transmissions, men were more likely to be reported as transmitted through CHC, while the opposite was true for women. Furthermore, the ratio of males to females was much higher in the CHC group than in the NMNCHC group. This significant difference in the male-female ratio between CHC and NMNCHC indicates that men are more likely to be infected through CHC, while women are more likely to be infected through NMNCHC, but such a large difference in the proportion requires further study of the underlying causes. To explore the differences in the distribution and changing status of PLWHA frequency between CHC and NMNCHC within various age periods, we analyzed the frequency distribution over the years by age group. It was found that the two transmission routes displayed a much larger difference in some age groups, which indicated that age plays a crucial role in heterosexual transmission routes and should be fully considered when establishing prevention and control strategies.

In general, the average age of the CHC group was much higher than that of the NMNCHC group, which was mainly due to the much higher number of those infected through CHC over the age of 60, as well as the much lower frequency in cases under 60. In the meantime, the age difference between the two groups was mainly due to men. This discovery supports some other study findings that there is an increasing rate of HIV infection among older people [30‐32], and that they were playing a more important role in local transmission [33]. Studies have found that many older Chinese adults remain sexually active [34, 35], and erectile dysfunction medications (EDMs) have become popular among older men to enhance sexual desire and performance [36]. Quite a number of older men choose low-end FSWs to satisfy their sexual needs [31], and due to the higher HIV prevalence among low-end FSWs [37], older adults’ lack of HIV/AIDS-related knowledge [34], and their unwillingness to use condoms during commercial sexual behavior [38], infection among older adults has soared in recent years. Generally, studies targeted HIV epidemics among older adults mainly focused on the population aged ≥50 years [31, 33]. However, our study found that the number of CHC transmission reports among people over the age of 65 has increased significantly. Therefore, it may be necessary to conduct specific studies on this age group in future studies.

Compared with CHC, younger adults are more likely to be infected with HIV through NMNCHC. Our study also noticed that the sex ratio in the 25–29 age group of NMNCHC transmissions had increased significantly. This may be because men aged 25 to 29 are relatively more active sexually and more likely to have casual sex and concurrent relationships. One study explored casual sexual behaviors among 108 Yi villagers aged 15–35 years from Liangshan Prefecture in Sichuan Province and found that 66.7% of them reported multiple sexual partnerships. Only 21.3% reported ever having used a condom, and 56.9% were involved in concurrent sexual partnerships among network members in components of size ≥3 [39]. In other parts of China, the transmission of HIV via NMNCHC in this age group needs further study.

The marital status was significantly different between the groups in all of the years studied, something that is probably because unmarried people are more likely to be younger and engaged in a casual heterosexual relationship, while divorced or widowed people are more likely to be older and to be engaged in commercial heterosexual behavior. Our study also discovered that the proportion of married PLWHA was increasing among those reported as infected through NMNCHC. This may suggest that marriage is becoming less of a barrier to extramarital sexual behavior in China. Furthermore, as the educational level improved, the proportion of NMNCHC also increased. This is probably because the educational level may have an association with socioeconomic status, which may affect the way people seek sexual partners. Age might also play an important role in the difference of educational levels between the two groups. Further studies are needed to rule out the effects of confounders and to explore these factors’ influence on the likelihood of being infected through CHC or NMNCHC.

Given the significant increase in the number of reports of transmission through CHC among persons over the age of 65, further study of this population is necessary in order to understand the key determinants of HIV transmission among them. At the same time, the investigation into this group is likely to reveal those FSWs who have transmitted HIV to these elderly men, which is conducive to strengthening the management of low-end FSWs and achieving prevention and control of HIV transmission. Moreover, because older adults are normally less educated, we need to adopt more understandable ways for publicity and education [40]. These could be simple methods such as using pictures as well as simple and clear language in order to impart knowledge on AIDS prevention and control, thereby improving the awareness of HIV/AIDS and increasing the condom utilization rate in this group. Moreover, the increase in NMNCHC transmission in the younger age groups is more difficult to control than CHC transmission. NMNCHC transmission networks are likely to be more widespread and complex, and current research on transmission in this population is very limited. There is a need for further study to understand transmission networks and the new ways in which younger adults acquire sexual partners, so as to establish new preventative measures in response to these new modes. In addition, this study preliminarily explored the different characteristics of CHC and NMNCHC. However, due to the regional differences in the HIV epidemic in China, the specific epidemic characteristics of each region need to be investigated separately.

In summary, this is the first nationwide targeted analysis of the epidemic status of PLWHA infected through commercial and noncommercial contact in nonmarital heterosexual transmission. PLWHA infected through CHC and NMNCHC have different characteristics, such as age and gender, marital status and educational level. PLWHA reported as transmitted through CHC was increasingly more common among men aged 65 and above, and further research is needed to explore the reason for the rapid increase in newly identified PLWHA among this age group. NMNCHC played an increasingly significant role in heterosexual transmission, and PLWHA infected through NMNCHC were comparatively younger than those transmitted through CHC. Further study is necessary to understand the transmission characteristics of NMNCHC, such as the transmission networks and the new ways in which people obtain sexual partners. Our study provided useful basic data for the further exploration of the characteristics of the heterosexual transmission of HIV in China.