HIV-1 incidence among male workers at a sugar estate in rural Malawi

Analyzing spatial clustering and the spatiotemporal nature and trends of HIV/AIDS prevalence using GIS: the case of Malawi, 1994-2010

BACKGROUND

Although local spatiotemporal analysis can improve understanding of geographic variation of the HIV epidemic, its drivers, and the search for targeted interventions, it is limited in sub-Saharan Africa. Despite recent declines, Malawi's estimated 10.0% HIV prevalence (2011) remained among the highest globally. Using data on pregnant women in Malawi, this study 1) examines spatiotemporal trends in HIV prevalence 1994-2010, and 2) for 2010, identifies and maps the spatial variation/clustering of factors associated with HIV prevalence at district level.

METHODS

Inverse distance weighting was used within ArcGIS Geographic Information Systems (GIS) software to generate continuous surfaces of HIV prevalence from point data (1994, 1996, 1999, 2001, 2003, 2005, 2007, and 2010) obtained from surveillance antenatal clinics. From the surfaces prevalence estimates were extracted at district level and the results mapped nationally. Spatial dependency (autocorrelation) and clustering of HIV prevalence were also analyzed. Correlation and multiple regression analyses were used to identify factors associated with HIV prevalence for 2010 and their spatial variation/clustering mapped and compared to HIV clustering.

RESULTS

Analysis revealed wide spatial variation in HIV prevalence at regional, urban/rural, district and sub-district levels. However, prevalence was spatially leveling out within and across 'sub-epidemics' while declining significantly after 1999. Prevalence exhibited statistically significant spatial dependence nationally following initial (1995-1999) localized, patchy low/high patterns as the epidemic spread rapidly. Locally, HIV "hotspots" clustered among eleven southern districts/cities while a "coldspot" captured configurations of six central region districts. Preliminary multiple regression of 2010 HIV prevalence produced a model with four significant explanatory factors (adjusted R2 = 0.688): mean distance to main roads, mean travel time to nearest transport, percentage that had taken an HIV test ever, and percentage attaining a senior primary education. Spatial clustering linked some factors to particular subsets of high HIV-prevalence districts.

CONCLUSIONS

Spatial analysis enhanced understanding of local spatiotemporal variation in HIV prevalence, possible underlying factors, and potential for differentiated spatial targeting of interventions. Findings suggest that intervention strategies should also emphasize improved access to health/HIV services, basic education, and syphilis management, particularly in rural hotspot districts, as further research is done on drivers at finer scale.

Behavioral aspects of male circumcision for the prevention of HIV infection

Male circumcision (MC) can prevent female-to-male HIV transmission and has the potential to significantly alter HIV epidemics. The ultimate impact of MC on HIV prevention will be determined, in part, by behavioral factors. In order to fully realize the protective benefits of MC, factors related to acceptability and sexual risk must be considered. Research shows that acceptability of MC among uncircumcised men is high, and suggests that free and safe circumcision may be taken up in places with high HIV prevalence. Perceptions of adverse effects of MC may, however, limit uptake. Furthermore, considerable risk reduction counseling provided by MC trials limits our ability to understand the impact MC may have on behavior. There is also no evidence that MC protects women with HIV-positive partners or that it offers protection during anal intercourse. Research is urgently needed to better understand and manage the behavioral implications of MC for HIV prevention.

Circumcision and HIV infection: assessment of causality

Whether the observed association between male circumcision and HIV infection is causal or not has not been verified. We did a meta-analysis of published data and applied Hill's criteria for causality on all available evidence to assess presence of a causal association. Analysis was by the random effects method. Summary estimates were calculated for all studies combined and for sub groups stratified by type of study population, study design, and method of ascertaining circumcision status. Thirteen studies were included. Circumcised men had a reduced risk for HIV infection (adjusted RRoverall = 0.42, 95% CI 0.33-0.53; RR(RCT) = 0.43 95% CI 0.32-0.59, RRobservational = 0.39, 95% CI 0.27-0.56). Available evidence satisfies six of Hill's criteria: strength of association, consistency, temporality, coherence, biological plausibility, and experiment. These results provide unequivocal evidence that circumcision plays a causal role in reducing the risk of HIV infection among men.

Oral manifestations of syphilis

The past decade has shown a significant rise in the prevalence of infective syphilis in the developed world, and striking increases in its frequency have occurred in Eastern Europe, particularly the UK, and in the US. Although oral manifestations of syphilis are most likely to be observed during secondary disease, all stages of the disease can give rise to oral lesions. Significant oral lesions such as gumma-associated bony destruction and a possible predisposition to oral squamous cell carcinoma are associated with tertiary disease. Since the prevalence of infective syphilis in heterosexuals has been increasing, there has now been a gradual rise in the number of children born with congenital syphilis. Consequently, the congenital disease gives rise to dental anomalies as well as bone, skin, and neurological anomalies of the face. The aim of this report is to review syphilis-related oral lesions, as well as to summarize the relations between human immunodeficiency virus (HIV) and syphilis.

Interactive association of proviral load and IFN-gamma-secreting T cell responses in HIV-1C infection

We investigated the interactive relationship between proviral DNA load and virus-specific IFN-gamma-secreting T cell responses in HIV-1C infection. The presence or absence of correlation, and inverse or direct type of correlation, if any, were dependent on targeted viral gene product. Responses to Gag p24 or to Pol were associated with lower proviral DNA load. Associations between proviral DNA load and T cell responses did not necessarily mirror relationships between plasma RNA load and T cell responses. An interaction analysis showed a synergy in that lower proviral DNA and lower plasma RNA load were associated with high Gag p24-specific IFN-gamma-secreting T cell response (interaction test P = 0.0003). Our findings support the idea that HIV proteins have differential value for vaccine design, and suggest that, for HIV-1C, Gag p24 may be one of the most attractive regions to include in vaccine designs to control both plasma RNA load and cell-associated proviral DNA load.

Male circumcision for prevention of heterosexual acquisition of HIV in men

BACKGROUND

The findings from observational studies, reviews and meta-analyses, supported by biological theories, that circumcised men appear less likely to acquire human immunodeficiency virus (HIV) has contributed to the recent ground swell of support for considering male circumcision as a strategy for preventing sexually acquired infection. We sought to elucidate and appraise the global evidence from published and unpublished studies that circumcision can be used as an intervention to prevent HIV infection.

OBJECTIVES

1) To assess the evidence of an interventional effect of male circumcision for preventing acquisition of HIV-1 and HIV-2 by men through heterosexual intercourse 2) To examine the feasibility and value of performing individual person data (IPD) meta-analysis

SEARCH STRATEGY

We searched online for published and unpublished studies in The Cochrane Library (issue 2, 2002), MEDLINE (April 2002), EMBASE (February 2002) and AIDSLINE (August 2001). We also searched databases listing conference abstracts, scanned reference lists of articles and contacted authors of included studies.

SELECTION CRITERIA

We searched for randomized and quasi-randomized controlled trials of male circumcision or, in their absence, observational studies that compare acquisition rates of HIV-1 and HIV-2 infection in circumcised and uncircumcised heterosexual men.

DATA COLLECTION AND ANALYSIS

Independent reviewers selected studies, assessed study quality and extracted data. We stratified studies based on study design and on whether they included participants from the general population or high-risk groups (such as patients treated for sexually transmitted infections). We expressed findings as crude and adjusted odds ratios (OR) together with their 95% confidence intervals (CI) and conducted a sensitivity analysis to explore the effect of adjustment on study results. We investigated whether the method of circumcision ascertainment influenced study outcomes.

MAIN RESULTS

We identified no completed randomized controlled trials. Three randomized controlled trials are currently underway or commencing shortly. We found 34 observational studies: 16 conducted in the general population and 18 in high-risk populations. It seems unlikely that potential confounding factors were completely accounted for in any of the included studies. In particular, important risk factors, such as religion and sexual practices, were not adequately accounted for in many of the included studies. General population study results:The single cohort study (N = 5516) showed a significant difference in HIV transmission rates between circumcised and uncircumcised men [OR = 0.58; 95% CI: 0.36 to 0.96]. Results for the 14 cross-sectional studies were inconsistent, with point estimates for unadjusted odds ratios varying between 0.28 and 1.73. Six studies had statistically significant results, four in the direction of benefit and two in the direction of harm. The test for heterogeneity between the cross-sectional studies was highly significant (chi-square = 77.59; df = 13; P-value < 0.00001). Nine studies reported adjusted odds ratios with eight in the direction of benefit, ranging from 0.26 to 0.80. Use of adjusted results tended to show stronger evidence of an association although they remained heterogenous (chi-square = 75.2; df = 13; P-value < 0.00001). Only one case-control study was found (N = 51) which had a non-significant result [OR = 1.90; 95% CI: 0.50 to 7.20]. High-risk group study results:The four cohort studies identified found a protective effect from circumcision with point estimates for unadjusted odds ratios varying from 0.10 to 0.39. Two of these studies had statistically significant results. Two studies reported adjusted odds ratios, both protective with one being significant. The chi-square test for between-study heterogeneity was not significant (chi-square = 5.21; df = 3; P-value = 0.16). All eleven cross-sectional studies reporting unadjusted results found benefit from circumcision, eight of which had statistically significant results. Estimates of effnal studies reporting unadjusted results found benefit from circumcision, eight of which had statistically significant results. Estimates of effect varied from an unadjusted odds ratio of 0.10 to 0.66. Between-study heterogeneity was significant with the chi-square = 29.77; df = 10; P-value = 0.0009. Four of these studies reported adjusted odds ratios ranging from 0.20 to 0.59 and all were significant. One additional cross-sectional study only reported an adjusted odds ratio in the direction of benefit which was statistically significant. All three case-control studies found a protective effect of circumcision on HIV status, two being statistically significant. Point estimates varied from unadjusted odds ratios of 0.37 to 0.88. One reported an adjusted odds ratio showing a significant protective effect. Adverse effects:No studies reported on the adverse effects of circumcision. In most studies, circumcision had taken place during childhood or adolescence before the studies commenced.

REVIEWER'S CONCLUSIONS

We found insufficient evidence to support an interventional effect of male circumcision on HIV acquisition in heterosexual men. The results from existing observational studies show a strong epidemiological association between male circumcision and prevention of HIV, especially among high-risk groups. However, observational studies are inherently limited by confounding which is unlikely to be fully adjusted for. In the light of forthcoming results from RCTs, the value of IPD analysis of the included studies is doubtful. The results of these trials will need to be carefully considered before circumcision is implemented as a public health intervention for prevention of sexually transmitted HIV.

HIV-1 prevalence and herpes simplex virus 2, hepatitis C virus, and hepatitis B virus infections among male workers at a sugar estate in Malawi

HIV-1 prevalence is approximately 23% among men working at a sugar estate in Malawi. Given the scale of the HIV epidemic in this country, it is important to determine possible cofactors of infection. The authors investigated associations between HIV-1 prevalence and herpes simplex virus 2 (HSV-2), hepatitis C virus (HCV), and hepatitis B virus (HBV) infections (indicated by anti-HSV-2, anti-HCV and HBsAg positivity, respectively) in a nested case-control study of 279 HIV-positive and 280 HIV-negative male workers. The prevalence of HSV-2 infection was 88.1% among HIV-positive persons and 64.3% among HIV-negative control subjects (p <.01). This difference persisted after adjusting for sexual behavior and history of sexually transmitted diseases (OR = 4.12; 95% CI, 2.21-7.68). The prevalence of HCV seropositivity was 12.7% among HIV-positive persons and 10.0% among control subjects (p =.31), whereas that of HBV infection was 16.9% among HIV-positive persons and 14.4% among control subjects (p =.46). HSV-2 infection is significantly associated with prevalent HIV-1 infection in this population. Therefore, preventive measures for HSV-2 and HIV infection should be emphasized.

Three surveys of HIV-1 prevalence and risk factors among men working at a sugar estate in Malawi

BACKGROUND

HIV-1 surveys in defined populations identify underlying risks and trends useful to mount interventions.

GOAL

The goal of the study was to determine HIV-1 prevalence and risk factors among men working at a Malawian sugar estate.

STUDY DESIGN

Three independent surveys were conducted in 1994, 1997, and 1998. Procedures included obtaining informed consent, interviewing, and drawing blood for HIV and syphilis testing. Analyses determined prevalence of HIV and associated risk factors.

RESULTS

HIV prevalence was 24.3% in 1994 (n = 1691), 22.8% in 1997 (n = 615), and 20.9% in 1998 (n = 1354; P < 0.03). From 1994 to 1998, the percentage of subjects with a history of sexually transmitted disease (STD) decreased from 43.6% to 29.5% (P < 0.0001), accompanied by a substantial rise in STDs confirmed by physical examination (from 7.5% to 16.8%; P < 0.0001) and by laboratory testing for syphilis (from 6.5% to 10.4%; P < 0.0001). The percentage with multiple sex partners declined (from 62.0% to 35.2%; P < 0.0001), and condom use rose (from 10.9% to 18.9%; P < 0.0001). STDs were significantly associated with prevalent HIV infection each year.

CONCLUSIONS

The prevalence of HIV has remained relatively stable and high in this cohort.