An improved optimistic three-stage model for the spread of HIV amongst injecting intravenous drug users

We start off this paper with a brief introduction to modeling Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) amongst sharing, injecting drug users (IDUs). Then we describe the mathematical model which we shall use which extends an existing model of the spread of HIV and AIDS amongst IDUs by incorporating loss of HIV infectivity over time. This is followed by the derivation of a key epidemiological parameter, the basic reproduction number R0. Next we give some analytical equilibrium, local and global stability results. We show that if R0 &gte 1 then the disease will always die out. For R0 > 1 there is the disease-free equilibrium (DFE) and a unique endemic equilibrium. The DFE is unstable. An approximation argument shows that we expect the endemic equilibrium to be locally stable. We next discuss a more realistic version of the model, relaxing the assumption that the number of addicts remains constant and obtain some results for this model. The subsequent section gives simulations for both models confirming that if R0 &gte 1 then the disease will die out and if R0 > 1 then if it is initially present the disease will tend to the unique endemic equilibrium. The simulation results are compared with the original model with no loss of HIV infectivity. Next the implications of these results for control strategies are considered. A brief summary concludes the paper

Seismic Risk Analysis of Revenue Losses, Gross Regional Product and transportation systems.

Natural threats like earthquakes, hurricanes or tsunamis have shown seri- ous impacts on communities. In the past, major earthquakes in the United States like Loma Prieta 1989, Northridge 1994, or recent events in Italy like L’Aquila 2009 or Emilia 2012 earthquake emphasized the importance of pre- paredness and awareness to reduce social impacts. Earthquakes impacted businesses and dramatically reduced the gross regional product. Seismic Hazard is traditionally assessed using Probabilistic Seismic Hazard Anal- ysis (PSHA). PSHA well represents the hazard at a specific location, but it’s unsatisfactory for spatially distributed systems. Scenario earthquakes overcome the problem representing the actual distribution of shaking over a spatially distributed system. The performance of distributed productive systems during the recovery process needs to be explored. Scenario earthquakes have been used to assess the risk in bridge networks and the social losses in terms of gross regional product reduction. The proposed method for scenario earthquakes has been applied to a real case study: Treviso, a city in the North East of Italy. The proposed method for scenario earthquakes requires three models: one representation of the sources (Italian Seismogenic Zonation 9), one attenuation relationship (Sa- betta and Pugliese 1996) and a model of the occurrence rate of magnitudes (Gutenberg Richter). A methodology has been proposed to reduce thou- sands of scenarios to a subset consistent with the hazard at each location. Earthquake scenarios, along with Mote Carlo method, have been used to simulate business damage. The response of business facilities to earthquake has been obtained from fragility curves for precast industrial building. Fur- thermore, from business damage the reduction of productivity has been simulated using economic data from the National statistical service and a proposed piecewise “loss of functionality model”. To simulate the economic process in the time domain, an innovative businesses recovery function has been proposed. The proposed method has been applied to generate scenarios earthquakes at the location of bridges and business areas. The proposed selection method- ology has been applied to reduce 8000 scenarios to a subset of 60. Subse- quently, these scenario earthquakes have been used to calculate three system performance parameters: the risk in transportation networks, the risk in terms of business damage and the losses of gross regional product. A novel model for business recovery process has been tested. The proposed model has been used to represent the business recovery process and simulate the effects of government aids allocated for reconstruction. The proposed method has efficiently modeled the seismic hazard using scenario earthquakes. The scenario earthquakes presented have been used to assess possible consequences of earthquakes in seismic prone zones and to increase the preparedness. Scenario earthquakes have been used to sim- ulate the effects to economy of the impacted area; a significant Gross Regional Product reduction has been shown, up to 77% with an earthquake with 0.0003 probability of occurrence. The results showed that limited funds available after the disaster can be distributed in a more efficient way

Potential impact of adjustment policies on vulnerability of women and children to HIV/AIDS in sub-Saharan Africa

This paper evaluates the potential impact of adjustment policies of the International Monetary Fund and the World Bank on the vulnerability of women and children to HIV/AIDS in sub-Saharan Africa. A conceptual framework, composed of five different pathways of causation, is used for the evaluation. These five pathways connect changes at the macro level (e.g. removal of food subsidies) with effects at the meso (e.g. higher food prices) and micro levels (e.g. exposure of women and children to commercial sex) that influence the vulnerability of women and children to HIV/AIDS. Published literature on adjustment policies and socioeconomic determinants of HIV/AIDS among women and children in sub-Saharan Africa was reviewed to explore the cause-effect relationships included in the theoretical framework. Evidence suggests that adjustment policies may inadvertently produce conditions facilitating the exposure of women and children to HIV/AIDS. Complex research designs are needed to further investigate this relationship. A shift in emphasis from an individual approach to a socioeconomic approach in the study of HIV infection among women and children in the developing world is suggested. Given the potential for adjustment policies to exacerbate the AIDS pandemic among women and children, a careful examination of the effects of these policies on maternal and child welfare is urgently needed

The French ?Earned Income Supplement? (RSA) and back-to-work incentives

RMI, API, unemployment, means-tested benefits, back-to-work incentives.

Operational models for epidemic of problematic drug use: the Mover-Stayer approach to heterogeneity

A modified version of a susceptibles–infectives–removed (S–I–R) model for the HIV/AIDS epidemic, proposed at the beginning of the 1990s and recently generalized, is presented to mirror the epidemics of problematic drug use. The generalized model, which belongs to the susceptibles–infectives–susceptibles (S–I–S) class of epidemic models, can be used both to estimate interesting epidemic macro-parameters and to make scenario analyses. The model is a compartmental Mover–Stayer-type structure (Soc. Methods Res. 11 (1983) 345; Bull. Narcotics LIII (1-2) (2001) 39; Biometrics 55(4) (1999) 1252; Math. Biosci. 107 (1991) 521) and allows taking into account possible heterogeneous behaviours of the susceptibles. Such models, in fact, consider the susceptible population as subdivided into two main groups: the group of stayers, that is, the group of individuals who are considered not at risk of ‘‘infection’’, and the group of movers (possibly divided into sub-groups with different risk behaviour) who are at risk of infection. Due to the interactions between infectious individuals and the susceptibles, some of these may pass to the drug user compartments and begin a ‘‘drug user career’’. The model is presented and studied from a qualitative point of view using a Markov hybrid approximation. Some qualitative evaluation of the possible impact of interventions directed both towards susceptibles (primary prevention) and towards users (secondary prevention and/or law enforcement) are presented. Specific ‘‘what if’’ scenario analyses are obtained by simulation. Possible future developments are outlined

Institutions and economic policies for pro-poor agricultural growth

"This paper draws together findings from different elements of a research project examining critical components of pro-poor agricultural growth and of policies that can promote such growth in poor rural economies in South Asia and Sub-Saharan Africa. Agricultural growth, a critical driver in poverty reducing growth in many poor agrarian economies in the past, faces many difficulties in today's poor rural areas in South Asia and Sub-Saharan Africa. Some of these difficulties are endogenous to these areas while others result from broader processes of global change. Active state interventions in 'kick starting' markets in 20th century green revolutions suggest that another major difficulty may be current policies which emphasize the benefits of liberalization and state withdrawal but fail to address critical institutional constraints to market and economic development in poor rural areas. This broad hypothesis was tested in an analysis of the returns (in agricultural growth and poverty reduction) to different government spending in India over the last forty years. The results reject the alternate hypothesis underlying much current policy, that fertilizer and credit subsidies, for example, depressed agricultural growth and poverty reduction in the early stages of agricultural transformation. The results show initially high but then declining impacts from fertilizer subsidies; high benefits from investment in roads, education and agricultural R&D during all periods and varying benefits from credit subsidies over four decades; low impacts from power subsidies; and intermediate impacts from irrigation investments. These findings demand a fundamental reassessment of policies espousing state withdrawal from markets in poor agrarian economies. Given widespread state failure in many poor agrarian economies today, particularly in Africa, new thinking is urgently needed to find alternative ways of 'kick starting' markets ways which reduce rent seeking opportunities, promote rather than crowd-out private sector investment, and allow the state to withdraw as economic growth proceeds. Authors' AbstractAgricultural growth ,Poverty, Rural ,South Asia Rural poor ,Africa, Sub-Saharan ,Agrarian economies ,Globalization ,Green Revolution ,Poverty alleviation ,Government spending policy India ,

The epidemiological impact of antiretroviral use predicted by mathematical models: a review

This review summarises theoretical studies attempting to assess the population impact of antiretroviral therapy (ART) use on mortality and HIV incidence. We describe the key parameters that determine the impact of therapy, and argue that mathematical models of disease transmission are the natural framework within which to explore the interaction between antiviral use and the dynamics of an HIV epidemic. Our review focuses on the potential effects of ART in resource-poor settings. We discuss choice of model type and structure, the potential for risk behaviour change following widespread introduction of ART, the importance of the stage of HIV infection at which treatment is initiated, and the potential for spread of drug resistance. These issues are illustrated with results from models of HIV transmission. We demonstrate that HIV transmission models predicting the impact of ART use should incorporate a realistic progression through stages of HIV infection in order to capture the effect of the timing of treatment initiation on disease spread. The realism of existing models falls short of properly reproducing patterns of diagnosis timing, incorporating heterogeneity in sexual behaviour, and describing the evolution and transmission of drug resistance. The uncertainty surrounding certain effects of ART, such as changes in sexual behaviour and transmission of ART-resistant HIV strains, demands exploration of best and worst case scenarios in modelling, but this must be complemented by surveillance and behavioural surveys to quantify such effects in settings where ART is implemented

Globalization and Health: Impact Pathways and Recent Evidence

The last two decades of the twentieth century recorded a slowdown in health gains and widespread increases in health inequality across and within countries. The paper explores the causes of such trends on the basis of five main mortality models. To do so, it regresses IMR/LEB on 15 determinants of health. The results underscore the negative health effects of the trends observed between 1980-2000, such as rising inequality, greater income volatility, declining health expenditure, increasing migration and so on. Finally, the paper simulates the level of LEB that would have been achieved in ten regions of the world if the determinants of health had continued developing over these decades as they did over 1960-80. The results indicate that in seven of such regions (including China and India) LEB would have been higher than actually observed. In this regard, the paper raises doubts about the way globalization has taken place and the way public policy oriented it.health status, health inequalities, globalization