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  • There are major challenges in the estimation of the

    2019-07-01

    There are major challenges in the estimation of the prevalence of opioid use in Afghanistan. The country has been in a state of war and insurgency for the better part of 40 years; its Forskolin is widely dispersed and often very mobile; it has low levels of literacy; and Afghans are not accustomed to answering questions about a prohibited behaviour that are posed by a stranger in a survey interview. In , Linda B Cottler and colleagues used innovative methods to estimate the prevalence of recent use of drugs (including opioids, pharmaceutical drugs, and cannabis) in the Afghan population. As part of the Afghanistan National Urban Drug Use Study (ANUDUS), they interviewed the female heads of 2187 Afghan households about the drug use of all household members. The sample came largely from urban areas in more accessible and less dangerous provinces. Biological samples (hair, saliva, and urine) were obtained from three specified members of the household (oldest man, female head of the household, and youngest child aged 4–14 years) to validate the head of household reports of drug use (or its absence).
    When the Roll Back Malaria Partnership was launched in 1998, insecticide-treated nets (ITNs) were seen as the key malaria prevention tool to halt the raging malaria epidemic in Africa. A systematic review of several studies in endemic areas had shown that the use of ITNs reduced malaria mortality by 17% and clinical episodes by half. Since 2000, almost 2 billion US dollars have been invested in malaria control globally. Between 2004 and 2012, almost 600 million ITNs have been distributed in Africa. Over this period, studies have shown significant reductions in malaria infection prevalence in the continent and ITN coverage is likely to be an important driver of this decline. Despite the general consensus on the role of ITNs in reducing malaria infection rates in Africa, few studies have analysed their effect subnationally. Such an analysis is especially important given the spatially and temporally heterogeneous nature of malaria transmission and the dependence of the effectiveness of ITNs on the transmission intensity of an area. A major limitation has been the lack of nationally representative spatially and temporally comparable data that concurrently measure parasitaemia and access or use of ITNs among the population. Such data have become increasingly available since 2005, mainly through malaria indicator surveys and some demographic and health surveys. In this issue of , Federica Giardina and colleagues report their analysis of national household survey data from six countries (Angola, Liberia, Mozambique, Rwanda, Senegal, and Tanzania) that have had at least two surveys with data on both the use or access of ITNs, indoor residual spraying (IRS), and malaria infection rates among children younger than 5 years over the period 2006–12. Giardina and colleagues developed a Bayesian geostatistical approach to estimate the spatial effects of ITNs and/or IRS on malaria parasitaemia, after adjusting for time of survey, climatic factors, urbanisation, and socioeconomic status. They first used Bayesian geostatistical interpolation to predict malaria risk at 1×1 km spatial resolution at the two time periods for each country. From these they estimate the probability of parasitaemia risk reduction and the difference in the total number of children infected. They use a Bayesian variable selection approach to determine the most appropriate intervention indicator to the changing infection rates in a country. The analysis shows variable national and subnational levels of reductions of infection rates and effects of the vector control interventions. At the country level, the estimated decline between survey periods in the number of infections among children younger than 5 years was about 52% in Angola, 15% in Liberia, 42% in Rwanda, 40% in Senegal, and 30% in Tanzania; no change was seen in Mozambique. Changing ITN coverage seemed to have a significant effect on infection rates in Angola and Senegal but not in the other countries. Interestingly, however, in each country, subnational analysis showed reduction in parasitaemia and significant associations with ITN and/or IRS in some areas.