AIDS-Related Risky Behavioral Networks And Molecular Epidemiology In Taizhou Prefecture, Zhejiang Province

BackgroundTaizhou prefecture is a relatively low HIV prevalence area in China. The reported HIV infection in Taizhou prefecture continues to increase rapidly, especially during the recent 3 years. And sexual transmission is the primary route of transmission with homosexual transmission increasing rapidly. Traditional epidemiological researches on diseases mainly focus on independent individuals rather than as systems of interacting individuals. In recent years, researches applied risky behavioral network theory to the HIV control and prevention, which provide valuable insights into HIV transmission that might otherwise go unrecognized by routine practices. Presently, dynamic behavioral and molecular data of HIV transmission is still facing shortage in Taizhou prefecture and other relatively low HIV prevalence areas with sexual transmission as the primary route, which has seriously affected the development of comprehensive HIV prevention and control strategies effectively and scientifically.ObjectivesThe study was conducted in Taizhou prefecture, a low HIV-prevalence area in China with specific aims:(1) to trace and HIV-test those having risky contacts with HIV-infected individuals at various levels and characterize the risky behavioral networks among HIV infections and their contacts (with and without HIV infection) and its dynamic risky networks of HIV infections. (2) to reveal the dominant HIV subtypes and the reconstruction of the HIV transmission networks using a dated phylogeny approach and provide information of the HIV transmission dynamics among men who have sex with men (MSM). (3) to provide information of the parameterization of epidemiological and molecular models to design and improve intervention strategies for HIV control and prevention.Methods1. Tracing the sources of newly reported HIV infections in Taizhou prefecture All newly reported HIV infections from January 2008 through December 2010 in Taizhou prefecture were invited to participate in a cross-sectional survey which requested numbers and contact information of individuals with whom they had ever had high risk contacts as well as risky behavioral acts. Persons having had risky contacts with HIV-infected cases were thereof approached to participate in this contact tracing survey and receive HIV testing. Those who tested positive for HIV were subject to further round of contact tracing surveys.2. Cohort study on the HIV infections in Taizhou prefectureAll reported HIV infections before December of 2009 meet the admission criterion of the study were included to characterize the dynamic risky behavioral networks through a one-year follow up. Baseline and dynamic data on AIDS-related risky behaviors including numbers, type of the contacts and usage of the condom during the sexual intercourse was collected and compared when the HIV infections enrolled the cohort and were over a one-year follow-up.3. AIDS-related risky behavioral networks and molecular epidemiology study of newly reported HIV infected MSM in Taizhou prefectureAll newly reported HIV infected MSMs and their risky contacts during the study period from 2008 through 2010 were included into the study to identify the HIV infections and characterize the egocentric risky behavioral networks of the HIV infections with their contacts through contact tracing methods. Combined with behavioral network theory, reconstruction of HIV transmission egocentric risky behavior and viral genotypic networks among HIV-infected MSM was established using modern epidemiology and recently developed phylogenetics techniques.Main results1. Tracing the sources of newly reported HIV infections in Taizhou prefecture There were a total of 463 newly reported HIV infections and 462 HIV infections met the study criterion during the study period. Among those,398 newly reported HIV infections, with the paticipation rate of 86.1%, served as the'index cases'were included into the contact tracing and risky behavioral network study. Of those,396 cases with sexual experiences reported a total of 5,183 individuals with whom they had ever had sexual contacts, including HIV-infected MSM reporting a total of 1,534 male sexual partners. And 86.7% (343/396) of them reported multiple sexual partners (two or more sexual partners).There were a total of 288 independent egocentric sexual networks, including 29 egocentric sexual networks with both heterosexual and homosexual partners, were identified and 5.9%(17/288) of networks are dyads which included 2 members, 10.4% (30/288) included 3 to 5 members,19.1%(50/288) included 6 to 10 members, 33.7%(97/288) included 11 to 20 members,30.9%(89/288) included 21 members or more.398 HIV cases served as'index cases'reported totally 1,403 risky contacts with risky behavioral information. Among those,22.8%(320/1403) of contacts received HIV testing and 39.1% of the tested were positive for HIV. The study indicated that the highest HIV prevalence of the contacts those who come to receive HIV test was among spouses or regular heterosexual partners (34.9%,74/212) and male sexual partners of HIV-infected MSM (54.3%,53/94).2. Cohort study on the HIV infections in Taizhou prefecture In the study, a total of 285 HIV/AIDS infections enrolled the baseline study and 92.6%(264/285) of them completed the one-year follow-up. Among them,99.2% (262/264) reported that they have sexual behaviors before confirmation of HIV infection and reported a total of 4012 risky sexual contacts. The size of the whole network is 4274 and each participant had an average of 15.3±15.9 sexual partners.During the one-year follow-up period,63.6%(168/264) cases reported they had sexual behaviors and reported a total of 246 sexual partners and each participant had an average of 1.5+2.3 sexual partners. Of those infected with HIV through heterosexual contacts, their main types of sexual partners were commercial sexual partners (56.1%) before confirmation of HIV infection. However, at the baseline and during the recent one-year follow-up period, their main types of sexual partners changed to spouse or regular partners, about 50.1% and 84.4%, respectively. Of those infected with HIV through homosexual contacts, their main types of sexual partners were noncommercial causal sexual partners (57.3%) before confirmation of HIV infection. At the baseline and during the recent one-year follow-up survey, their main types of sexual partners changed to spouse or regular partners, about 55.4% and 52.4%, respectively. Of those infected with HIV through heterosexual contacts stratified by the time from baseline survey to HIV confirmation, before confirmation of HIV infection,75.0%-91.5% of them had sex with spouse or regular partners four times or above per month,69.4%-80.8% of them had never used condoms with their spouse or regular partner during their sexual intercourse.13.3%-35.7% and 37.5%-68.5% of them had sex with their noncommercial causal and commercial sexual partners four times or above per month, respectively. During their sexual intercourse,32.0%-46.2% and 21.8%-41.4% of them had never used condoms with their noncommercial causal and commercial sexual partners, respectively. During the recent one-year follow-up period,86.4%-91.1% of them had sex with their spouse or regular partners four times or above per month, and the proportion of participants who had consistent condom use with their spouse or regular partners increased to 90.9%-98.2% during their sexual intercourse. And they had consistent condom use with non-commercial causal and commercial sexual partners although they reported few noncommercial causal and commercial sexual partners. However, few HIV infections did not have consistent condom use during their sexual intercourse after their HIV confirmation. Of those infected with HIV through homosexual contacts, before the confirmation of HIV infection,100% of them had sex with high risky contacts four times or above per month and only 14.5% of them had consistent condom use during sexual intercourse. During the recent one-year follow-up period, 94.7% of them had sex with high risky contacts four times or above per month and 54.5% of them had consistent condom use. However, there were 40.9% of HIV-infected MSM who sometimes used condom during their intercourse in the recent one year of the study.3. AIDS-related risky behavioral networks and molecular epidemiology study among MSM in Taizhou prefectureTotally 111 HIV cases were newly reported during the study period. Among those, 101 cases participated in the contact tracing survey and served as'index cases', including 49 cases identified from the first round contact tracing and 3 cases identified from the second round. Epidemiological study indicated that the median number of the high risky contacts that index cases reported was 8 (min:1, max:80),23.8% of the 'index cases'reported they had more than 21 high risky contacts and 20.8% reported that they had 11 to 20 high risky contacts.90% of them reported their main type of sexual partner was male sexual partners, and 6.6% of them had consistent condom use during their sexual intercourse. There are three HIV-subtypes including CRF01_AE, CRF07_BC and B among the HIV infected MSM in Taizhou prefecture. CRF01_AE was the dominant subtype in Taizhou prefecture, which accounted for 73.3% and 72.1% respectively, when using the phylogenic analysis of the nucleotide sequences of the env and gag gene. In addition,2 cases were found to have recombinant strain related to both CRF01_AE and CRF07_BC,2 cases were found to have CRF01_AE and B, and another 3 cases were found to have CRF07_BC and B.On the basis of phylogenic analysis of the nucleotide sequences of the env and gag gene and epidemiological survey on AIDS-related risky behaviors, at least two or more epidemiologically linked HIV infected individuals among each of the 18 clusters were identified to have direct HIV transmission by viral genetic evidence of close match with sequence and genetic distance. Whereas, there were 6 clusters of discordance between epidemiologically linked with HIV sequence isolated, which reflected that individuals HIV sequence isolated rejected direct HIV transmission on the basis of genetic distance and phylogenetic tree. And for another 11 clusters, direct HIV transmission can not be identified due to negative PCR for the low HIV virus load less than the limit of detection of some HIV infections among the risky behavioral networks or other reasons. In addition, some epidemiologically unlinked clusters had isolated with matching HIV sequence, which suggested that some HIV infected individuals among the clusters may share the same source of HIV infection.Conclusion1. Contact tracing, the practice of identifying HIV infections has been confirmed to be successful in both high and low HIV-prevalence areas. Contact tracing, as a supplement to routine contact investigations to identify unrecognized HIV infections, adds a comprehensive public health approach to the epidemic that will be successful in reducing the ever-escalating numbers of new HIV infections.2. Newly reported HIV infections in Taizhou prefecture reported a large and complicated risk behavioral networks and low rate of condom use, suggesting a potential risk of HIV transmission among these connected people, especially among MSM.3. After their HIV confirmation and comprehensive intervention, the dynamic behavioral networks of the HIV infections changed from the large, complicated networks to a small, simple one over time and the main types of sexual partner changed from non-regular, non-spouse sexual partner to regular or spouse sexual partner, which do not facilitate the HIV transmission.4. Reconstruction of the HIV transmission network using modern epidemiology and a dated phylogenetic tree analysis approach has revealed a large and complicated risk behavioral networks and HIV transmission among MSM in Taizhou prefecture. CRF01_AE was the dominant epidemic CRF strains among the MSM of Taizhou prefecture while the subtype B and CRF07_BC were also circulating among MSM in Taizhou prefecture. The updated phylogenetic tree analysis approach combined modern epidemiology provides valuable insights into HIV transmission that might otherwise go unrecognized by routine practices. The quantitative description of the transmission dynamics among MSM will be important for parameterization of epidemiological models and designing intervention strategies.