HIV is one of the most influential infectious diseases in the world, and the spread of HIV virus through HIV serodiscordant couples is a transmission route that cannot be ignored. Risk of HIV transmission is determined by factors such as the possibility of exposure to the infected individuals and explicit sexual activity [24]. Some studies have even carefully described the specific mechanisms of HIV sexual transmission [25]. In this study, we analyzed a total of four factors related to HIV transmission among HIV serodiscordant couples: whether or not they received ART, occupation (farmers or non-farmers), infection route of index case (intravenous drug abuse or heterosexual intercourse), and disease stage (HIV or AIDS). Among these factors, ART, occupation and infection route of index case had a significant relationship with the HIV seroconversion rate in HIV serodiscordant couples.
Our meta-analysis shows that the HIV seroconversion rate in couples who received ART was lower than in couples who did not receive ART. However, not all studies confirmed the effect of ART. One study showed that after 2 years of ART, 33% of the patients experienced virological treatment failure [26]. Another study conducted in Zhejiang province showed that from 2009 -2013, the HIV seroconversion rate increased slightly in the ART group (from 0.0/1000 PY in 2009 to 3.0/1000 PY), but decreased in those without ART (from 24.10/1000 PY in 2009 to 5.56/1000 PY in 2013) [15]. These results may be explained by the Chinese government’s emphasis on HIV transmission in families, with HIV testing of couples being a key task since 2010. In addition to increased intervention capacity of grassroots workers, these measures have reduced the risk of HIV infection in untreated couples. Further, couples that receive ART are tested once a year, although the time interval between HIV seroconversion and ART may be shorter—making results appear as if the preventive effect of ART has not yet been achieved.
Factors affecting ART outcomes are increasingly being reported. Several studies included in our analysis explored the effects of ART interventions in the HIV infection and AIDS stages,but due to different definitions of disease staging, we could not conduct a meta-analysis of this outcome. A large-scale clinical trial of ANRS 12249 in South Africa found that early initiation of ART had no effect on HIV incidence [27], which is contrary to existing theoretical knowledge. During the follow-up of patients receiving ART therapy, we found that they have further improved their awareness of AIDS and become more aware of the safety of sexual behavior, such as the reduction of sexual intercourse and the increase of condom use. Therefore, early and long-term acceptance of ART can not only reduce the viral load in patients, but also carry out health education in the process of intervention. Although the effectiveness of ART needs to be subdivided and explored from different angles to achieve long-term suppression of HIV in patients who need lifetime ART, it is still considered necessary to promote ART therapy in general.
The disease stage of AIDS doesn’t always mean the higher seroconversion rate than HIV infection. According to general theoretical knowledge, patients with AIDS have fewer CD4 cells, more copies of the virus, and a greater probability of HIV transmission. However, the clinical symptoms of patients with AIDS could be more serious. Such couples likely use more measures to protect the uninfected partner from HIV infection, partially offsetting other adverse effects of AIDS. In addition, related studies have found that not all HIV-infected individuals are identified, especially patients with acute and early infections, which are the most infectious [26]. If one individual of a couple was infected with HIV and the symptoms had not yet manifested, the infectiousness of HIV may be underestimated. Indeed, because HIV has an incubation period, patients vary in the length of time from diagnosis of HIV infection to development of AIDS. Evidence to describe the difference in risk of seroconversion between these periods could guide medical resources more effectively.
The HIV-infected population in rural central China is likely the largest known HIV-infected cohort in the world[28]. Due to the limitations of the medical environment and the challenges in identifying these cases, this subset of HIV serodiscordant couples may have an increased HIV seroconversion rate. Meta-analysis of occupation also showed that HIV seroconversion rate was significantly higher in farmers. A less educated index case is more likely to pass the HIV virus to others due to a lack of awareness [29]. At present, rural regions that represent a major portion of HIV cases are important considerations for disease control. However, due to the low level of education and lack of health knowledge, farmers are resistant to HIV interventions and the vast majority of rural residents do not understand government policies and social health service resources. Our results highlight the need for an AIDS prevention model specifically targeted at farmers, with a focus on increasing awareness of and education about AIDS.
Analysis by infection route of the index case revealed that those who injected drugs were more likely to transmit the HIV virus than those having heterosexual intercourse. Further, the effect of ART in patients infected through heterosexual intercourse is better than in those infected by injection drug use [26]. Patients infected by drug injection have poor cognitive ability and treatment compliance, which may partially account for these results [30]. This suggests that drug injection has become a significant factor in seroconversion. Some people addicted to drugs choose to share syringes to meet their needs, despite knowing the risk of HIV infection. Spouses of injecting drug users may also be willing to take the risk despite not injecting drugs themselves. Relevant institutions should pursue interventions that reduce injection drug use and educate drug users on the risk of spreading HIV to their spouses.
Our results are novel; we have not found any other studies that explore factors that may influence HIV seroconversion rate. Further, our research content is relatively comprehensive and studies not only the effects of ART (the most popular topic of research), but also factors that are often overlooked, such as infection route of the index case, which is sometimes related to the HIV seroconversion rate. Other factors that should theoretically be related to HIV seroconversion rate, such as disease stage, may have no effect. In addition, our inclusion of external intervention factors and patients’ own conditions make the results more accurate.
This study also had some limitations. We found large heterogeneity in ART studies. Subgroup analysis indicated heterogeneity may arise from the study area, which was over-dispersed. Sensitivity analysis of infection route of index case indicated no difference between the two routes when we excluded a heavily weighted article, indicating that this article likely influenced overall results. Therefore, more research is needed on the infection route of index case. Egger’s regression asymmetry tests showed different degrees of publication bias in all results except ART. In addition, it was impossible to require all the included articles to be prospective studies because few articles examined factors affecting the HIV seroconversion rate. The varied research methods of included articles may also have complicated our results. Yet, after combining analysis of the existing literature with the test of heterogeneity and sensitivity, we consider these results persuasive.