***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Observational studies suggest that male circumcision may provide protection against HIV-1 infection .  A r and omized , controlled intervention trial was conducted in a general population of South Africa to test this hypothesis . Methods and Findings A total of 3,274 uncircumcised men , aged 18–24 y , were r and omized to a control or an intervention group with follow-up visits at months 3 , 12 , and 21 . Male circumcision was offered to the intervention group immediately after r and omization and to the control group at the end of the follow-up . The grouped censored data were analyzed in intention-to-treat , univariate and multivariate , analyses , using piecewise exponential , proportional hazards models . Rate ratios ( RR ) of HIV incidence were determined with 95 % CI . Protection against HIV infection was calculated as 1 − RR . The trial was stopped at the interim analysis , and the mean ( interquartile range ) follow-up was 18.1 mo ( 13.0–21.0 ) when the data were analyzed . There were 20 HIV infections ( incidence rate = 0.85 per 100 person-years ) in the intervention group and 49 ( 2.1 per 100 person-years ) in the control group , corresponding to an RR of 0.40 ( 95 % CI : 0.24%–0.68 % ; p < 0.001 ) . This RR corresponds to a protection of 60 % ( 95 % CI : 32%–76 % ) . When controlling for behavioural factors , including sexual behaviour that increased slightly in the intervention group , condom use , and health-seeking behaviour , the protection was of 61 % ( 95 % CI : 34%–77 % ) . Conclusion Male circumcision provides a degree of protection against acquiring HIV infection , equivalent to what a vaccine of high efficacy would have achieved . Male circumcision may provide an important way of reducing the spread of HIV infection in sub-Saharan Africa . ( Preliminary and partial results were presented at the International AIDS Society 2005 Conference , on 26 July 2005 , in Rio de Janeiro , Brazil . To better underst and the reasons why up to 80 % of all HIV-1 infections in Zaire , but less than 5 % in North America and Europe , are acquired through heterosexual transmission , and to assess the impact of HIV-1 infection on a large urban African workforce , we enrolled 7068 male employees , 416 female employees and 4548 female spouses of employees at two large Kinshasa businesses ( a textile factory and a commercial bank ) in a prospect i ve study of HIV-1 infection . The HIV-1 seroprevalence rate was higher in male employees ( 5.8 % ) and their spouses ( 5.7 % ) at the bank than among male employees ( 2.8 % ) and their spouses ( 3.3 % ) at the textile factory . At both businesses HIV-1 seroprevalence was higher among employees in managerial positions ( 5.0 % ) than among workers in lower-level positions ( 3.0 % ; P less than 0.0001 ) . In a multivariate analysis of male employees , receipt of a transfusion , a history of genital ulcer disease , working at the bank , urethritis , or being divorced or separated were independently associated with HIV-1 infection . During 1987 and 1988 , AIDS was the most common cause of death among recently employed workers , accounting for 20 and 24 % of all deaths at the textile factory and the commercial bank , respectively . The HIV-1 seroprevalence rate was higher among female workers ( 7.7 % ) than among the spouses of male workers ( 3.9 % ; P = 0.001 ) . In multivariate analysis of the wives of workers , having an HIV-1-seropositive spouse , receipt of a blood transfusion , or a history of genital ulcer disease were independently associated with HIV-1 infection . ( ABSTRACT TRUNCATED AT 250 WORDS We investigate the prevalence of , and risk factors for , HIV infection among women in an urban South African setting . A r and om sample of 834 women was recruited into a  community-based cross-sectional  study . HIV prevalence was 37.1 % with higher prevalence among migrant women ( 46.0 % ) than non-migrant women ( 34.7 % ) , ( odds ratio [OR]=1.61 , 95 % confidence interval [ CI ] : 1.11 - 2.31 ) . The highest HIV prevalence ( 50.9 % ) was between ages 26 and 35 years . Having two or more lifetime partners increased the risk of HIV infection ( OR=4.88 , 95 % CI : 3.01 - 7.89 ) . Migration , age , marital status , alcohol use , syphilis and gonorrhoea were independently associated with HIV infection . Migration increases the risk of HIV infection . Provision of services to treat sexually transmitted diseases and educational empowerment programmes that will promote safer sex among migrant women are urgently needed Objectives : To measure the prevalence of HIV and other STIs in communities neighbouring new large scale gold mines in northern Tanzania in order to inform the design of a targeted HIV/STI intervention programme . Methods : Cross sectional surveys were conducted in adults aged 16–54 years from different sectors of communities neighbouring two newly opened , large scale gold mines near Lake Victoria . Mine workers , men , women , and female food and recreational facility workers ( FRFW ) from the community were r and omly selected for interview and HIV and STI testing . Results : 207 male Tanzanian mine workers , 206 FRFW , 202 other male and 205 female community members were enrolled . Overall , 42 % of FRFW were HIV positive , compared to 6 % of male mine workers , and 16 % and 18 % of other community men and women respectively . HIV prevalence in FRFW was significantly associated with alcohol consumption ( adjusted odds ratio ( aOR ) = 2.5 , 95 % confidence interval ( CI ) 1.1 to 5.5 ) , past or present syphilis ( TPPA+ ) ( aOR = 2.7 , 95 % CI 1.4 to 5.1 ) and single status ( aOR = 3.8 , 95 % CI 1.2 to 11.9 ) . Among FRFW , 24 % had active syphilis ( RPR+ , TPPA+ ) , 9 % Chlamydia trachomatis , and 4 % Neisseria gonorrhoeae . Overall , 50 % of FRFW and 50 % of community men never used condoms during sex , and 55 % mineworkers , 61 % male , and 20 % female community members reported receiving/giving payment for sex during the previous year . Conclusions : There is a high prevalence of HIV and other STIs in communities around new goldmines in Tanzania , especially in FRFW .  HIV and STI prevalence in the mining workforce is still relatively low , but high risk sexual behaviour is reported by all adult subgroups surveyed in this study . Programmes focusing on HIV/STI prevention , with targeted interventions for high risk women such as FRFW , will be extremely important in such high transmission communities where there is substantial recent in-migration of men and women seeking work . Such programmes have recently been initiated by a private/public/NGO partnership Goals : We assessed baseline prevalence of human immunodeficiency virus type 1 ( HIV-1 ) and other STDs , as well as behavioral and biologic risk factors for HIV-1 in a population of female bar/hotel workers in Moshi , Tanzania . Study Design : Between 2002 and 2003 , we enrolled 1042 female bar/hotel workers in an ongoing prospect i ve cohort study . We analyzed data collected at baseline to assess the associations between alcohol , sexual behavior , STDs , and HIV-1 infection . Results : The prevalence of HIV-1 infection was 19.0 % ( 95 % confidence interval [ CI ] = 16.6%–21.4 % ) . Consistent condom use was low ( 11.1 % ) . HIV-1 was associated with genital ulcers on examination ( adjusted odds ratio [ AOR ] = 2.08 , 95 % CI = 1.16–3.74 ) , herpes simplex virus type 2 ( HSV-2 ) ( AOR = 3.80 , 95 % CI = 2.42–5.97 ) , and problem drinking ( AOR = 1.92 , 95 % CI = 1.06–3.47 ) . Other independent predictors of HIV-1 were increasing age , number of sex partners , cohabitating , formerly married , location of employment , and having a husb and with another wife . Conclusions : These findings suggest that programs design ed to control HSV-2 , reduce the number of sexual partners and alcohol use , and promote condom use could be effective in reducing transmission of HIV-1 in this population Objective To determine the prevalence of  HIV-1 infection  and to identify the most important risk factors for infection . Design A cross-sectional population survey  carried out in 1990 and 1991 in Mwanza Region , Tanzania . Methods Adults aged 15–54 years were selected from the region ( population , 2 million ) by stratified r and om cluster sampling : 2434 from 20 rural villages , 1157 from 20 roadside settlements and 1554 from 20 urban wards . Risk factor information was obtained from interviews . All sera were tested for  HIV-1 antibodies  using enzyme-linked immunosorbent assay ( ELISA ) ; sera non-negative on ELISA were also tested by Western blot . Results The response rate was 81 % . HIV-1 infection was 1.5 times more common in women than in men ; 2.5 % of the adult population in rural villages , 7.3 % in roadside settlements and 11.8 % in town were infected . HIV-1 infection occurred mostly in women aged 15–34 years and men aged 25–44 years . It was associated with being separated or widowed , multiple sex partners , presence of syphilis antibodies , history of genital discharge or genital ulcer , travel to Mwanza town , and receiving injections during the previous 12 months , but not with male circumcision . Conclusion This study confirms that  HIV-1 infection in this region in East Africa is more common in women than in men . The results are consistent with the spread of HIV-1 infection along the main roads . There is no evidence that lack of circumcision is a risk factor in this population Objectives : To determine the risk factors for HIV seroconversion and assess the association between contraceptive use and HIV infection among women attending three large family planning clinics in Dar es Salaam , Tanzania . Design : Prospect i ve cohort study . Methods : Between 1992 and 1995 , 2471 HIV-negative women were followed prospect ively . Information about  sociodemographic characteristics , sexual behavior , contraceptive use  and other risk factors was collected at recruitment and up date d at follow-up visits . At the end of the study , specimens were collected for HIV testing and laboratory diagnosis of sexually transmitted diseases . Results : The overall HIV incidence was 3.4 per 100 person-years [ 95 % confidence interval ( CI ) , 2.6–4.1 ] . The risk of HIV seroconversion decreased with increasing age ( P = 0.04 , test for trend ) . Women reporting three or more sex partners during the follow-up period had the highest risk of HIV [ age-adjusted relative risk ( RR ) , 4.89 ; 95 % CI , 2.6–9.17 ] . Having an uncircumcised husb and was associated with a significantly increased risk of HIV ( age-adjusted RR , 3.60 ; 95 % CI , 1.1–11.59 ) . The risk of HIV was also significantly increased among women with gonorrhoea ( age-adjusted RR , 3.51 ; 95 % CI , 1.6–7.71 ) and c and idiasis at baseline ( age-adjusted RR , 1.98 ; 95 % CI , 1.1–3.33 ) and among women reporting alcohol consumption during the follow-up period . After controlling for other risk factors , the risk of HIV infection amongst users of oral contraceptive , intrauterine device and injectable contraceptive was not significantly increased . Similarly , there was no significant trend associated with increasing duration of use of any of these contraceptive methods . Conclusion : These findings confirm that a large number of new HIV infections continue to occur in this population . Reassuringly , no significant association was observed between HIV and use of specific contraceptive methods . Interventions to reduce further spread of HIV are still urgently needed Background Vitamin A is involved in normal immune function and the maintenance of mucosal integrity through complex effects on cellular differentiation . Objective We sought to determine whether serum vitamin A levels were associated with altered susceptibility to primary infection with HIV-1 in men with high-risk sexual behaviour and genital ulcers who presented for treatment at an STD clinic in Nairobi , Kenya . Methods HIV-1 seronegative men were prospect ively followed . Vitamin A levels at study entry were compared among 38 men who HIV-1 seroconverted versus 94 controls who remained HIV seronegative . Results Vitamin A deficiency ( retinol less than 20 μg/dl ) was very common and was present in 50 % of HIV-1 seroconverters versus 76 % of persistent seronegatives . S 
    Output:
    
These risks changed little over time and stratification by lower and higher HIV background prevalence showed that risk ratios for most variables were larger in high prevalence setting s. Among uninfected controls , the male-female differences in the number of sex partners and in paid sex were more extreme in the higher HIV prevalence setting s than in the lower prevalence setting s. SIGNIFICANCE Multi-partner sex , paid sex , STIs and HSV-2 infection are as important to HIV transmission in advanced as in early HIV epidemics .
Even in high prevalence setting s , prevention among people with high rates of partner change , such as female sex workers and their male clients , is likely to reduce transmission overall