Test and treat — community perspectives

Présentation oraleInternational audiencen.

Integrable discretizations of the sine-Gordon equation

The inverse scattering theory for the sine-Gordon equation discretized in space and both in space and time is considered.Comment: 18 pages, LaTeX2

On dissipationless shock waves in a discrete nonlinear Schr\"odinger equation

It is shown that the generalized discrete nonlinear Schr\"odinger equation can be reduced in a small amplitude approximation to the KdV, mKdV, KdV(2) or the fifth-order KdV equations, depending on values of the parameters. In dispersionless limit these equations lead to wave breaking phenomenon for general enough initial conditions, and, after taking into account small dispersion effects, result in formation of dissipationless shock waves. The Whitham theory of modulations of nonlinear waves is used for analytical description of such waves.Comment: 15 pages, 9 figure

Factors associated with unprotected anal intercourse among men who have sex with men in Douala, Cameroon

Objectives Research on men who have sex with men (MSM) in sub-Saharan Africa was neglected for a long time. The objective of this study was to understand factors associated with unprotected anal intercourse (UAI) with male partners among a group of MSM living in the city of Douala, Cameroon. Methods In 2008, a survey on the sexual activity and practices of MSM was set up in Douala in collaboration with a local community-based organisation. Data were collected among a convenience sample of 168 MSM during face-to-face interviews with trained interviewers. Results A total of 142 individuals reported sexual activity during the previous 6 months, among whom 80 (57%) reported UAI with male partners. In a multivariate logistic regression model adjusted for the frequency of sexual intercourse, not having had access to prevention interventions and not knowing any HIV-infected person were both independently associated with a higher risk of UAI. Other factors associated with this higher risk included having had a stable male partnership at some point in one's life and not having been out of Douala for more than 4 weeks during the previous year. Conclusions This community-based research is the first study of MSM in Cameroon and the HIV transmission risks they face. Results show the importance of HIV prevention interventions from peers, and underline the need to maintain efforts to develop specific interventions targeting MSM more efficiently in the African context

An integrable discretization of KdV at large times

An "exact discretization" of the Schroedinger operator is considered and its direct and inverse scattering problems are solved. It is shown that a differential-difference nonlinear evolution equation depending on two arbitrary constants can be solved by using this spectral transform and that for a special choice of the constants it can be considered an integrable discretization of the KdV equation at large times. An integrable difference-difference equation is also obtained.Comment: 12 page

Earlier versus later start of antiretroviral therapy in HIV-infected adults with tuberculosis.

Tuberculosis remains an important cause of death among patients infected with the human immunodeficiency virus (HIV). Robust data are lacking with regard to the timing for the initiation of antiretroviral therapy (ART) in relation to the start of antituberculosis therapy

The Zakharov-Shabat spectral problem on the semi-line: Hilbert formulation and applications

The inverse spectral transform for the Zakharov-Shabat equation on the semi-line is reconsidered as a Hilbert problem. The boundary data induce an essential singularity at large k to one of the basic solutions. Then solving the inverse problem means solving a Hilbert problem with particular prescribed behavior. It is demonstrated that the direct and inverse problems are solved in a consistent way as soon as the spectral transform vanishes with 1/k at infinity in the whole upper half plane (where it may possess single poles) and is continuous and bounded on the real k-axis. The method is applied to stimulated Raman scattering and sine-Gordon (light cone) for which it is demonstrated that time evolution conserves the properties of the spectral transform.Comment: LaTex file, 1 figure, submitted to J. Phys.

Addressing social issues in a universal HIV test and treat intervention trial (ANRS 12249 TasP) in South Africa: methods for appraisal

Background: The Universal HIV Test and Treat (UTT) strategy represents a challenge for science, but is also a challenge for individuals and societies. Are repeated offers of provider-initiated HIV testing and immediate antiretroviral therapy (ART) socially-acceptable and can these become normalized over time? Can UTT be implemented without potentially adding to individual and community stigma, or threatening individual rights? What are the social, cultural and economic implications of UTT for households and communities? And can UTT be implemented within capacity constraints and other threats to the overall provision of HIV services? The answers to these research questions will be critical for routine implementation of UTT strategies. Methods/design: A social science research programme is nested within the ANRS 12249 Treatment-as-Prevention (TasP) cluster-randomised trial in rural South Africa. The programme aims to inform understanding of the (i) social, economic and environmental factors affecting uptake of services at each step of the continuum of HIV prevention, treatment and care and (ii) the causal impacts of the TasP intervention package on social and economic factors at the individual, household, community and health system level. We describe a multidisciplinary, multi-level, mixed-method research protocol that includes individual, household, community and clinic surveys, and combines quantitative and qualitative methods. Discussion: The UTT strategy is changing the overall approach to HIV prevention, treatment and care, and substantial social consequences may be anticipated, such as changes in social representations of HIV transmission, prevention, HIV testing and ART use, as well as changes in individual perceptions and behaviours in terms of uptake and frequency of HIV testing and ART initiation at high CD4. Triangulation of social science studies within the ANRS 12249 TasP trial will provide comprehensive insights into the acceptability and feasibility of the TasP intervention package at individual, community, patient and health system level, to complement the trial's clinical and epidemiological outcomes. It will also increase understanding of the causal impacts of UTT on social and economic outcomes, which will be critical for the long-term sustainability and routine UTT implementation. Trial registration: Clinicaltrials.gov: NCT01509508; South African Trial Register: DOH-27-0512-3974