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  1. 1
    182210
    Peer Reviewed

    Prediction of community prevalence of human onchocerciasis in the Amazonian onchocerciasis focus: Bayesian approach. [Prévisions portant sur la prévalence communautaire de l'onchocercose humaine au niveau du foyer amazonien de l'onchocercose : approche bayésienne]

    Carabin H; Escalona M; Marshall C; Vivas-Martinez S; Botto C

    Bulletin of the World Health Organization. 2003 Jul; 81(7):482-490.

    Objective: To develop a Bayesian hierarchical model for human onchocerciasis with which to explore the factors that influence prevalence of microfilariae in the Amazonian focus of onchocerciasis and predict the probability of any community being at least mesoendemic (>20% prevalence of microfilariae), and thus in need of priority ivermectin treatment. Methods: Models were developed with data from 732 individuals aged515 years who lived in 29 Yanomami communities along four rivers of the south Venezuelan Orinoco basin. The models’ abilities to predict prevalences of microfilariae in communities were compared. The deviance information criterion, Bayesian P-values, and residual values were used to select the best model with an approximate cross-validation procedure. Findings: A three-level model that acknowledged clustering of infection within communities performed best, with host age and sex included at the individual level, a river-dependent altitude effect at the community level, and additional clustering of communities along rivers. This model correctly classified 25/29 (86%) villages with respect to their need for priority ivermectin treatment. Conclusion: Bayesian methods are a flexible and useful approach for public health research and control planning. Our model acknowledges the clustering of infection within communities, allows investigation of links between individual- or community-specific characteristics and infection, incorporates additional uncertainty due to missing covariate data, and informs policy decisions by predicting the probability that a new community is at least mesoendemic. (author's)
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  2. 2
    182174
    Peer Reviewed

    Strategies for control of trachoma: observational study with quantitative PCR.

    Solomon AW; Holland MJ; Burton MJ; West SK; Alexander ND

    Lancet. 2003 Jul 19; 362(9379):198-204.

    Background: Antibiotics are an important part of WHO’s strategy to eliminate trachoma as a blinding disease by 2020. At present, who needs to be treated is unclear. We aimed to establish the burden of ocular Chlamydia trachomatis in three trachomaendemic communities in Tanzania and The Gambia with real-time quantitative PCR. Methods: Conjunctival swabs were obtained at examination from 3146 individuals. Swabs were first tested by the qualitative Amplicor PCR, which is known to be highly sensitive. In positive samples, the number of copies of omp1 (a single-copy C trachomatis gene) was measured by quantitative PCR. Findings: Children had the highest ocular loads of C trachomatis, although the amount of pooling in young age groups was less striking at the site with the lowest trachoma frequency. Individuals with intense inflammatory trachoma had higher loads than did those with other conjunctival signs. At the site with the highest prevalence of trachoma, 48 of 93 (52%) individuals with conjunctival scarring but no sign of active disease were positive for ocular chlamydiae. Interpretation: Children younger than 10 years old, and those with intense inflammatory trachoma, probably represent the major source of ocular C trachomatis infection in endemic communities. Success of antibiotic distribution programmes could depend on these groups receiving effective treatment. (author's)
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  3. 3
    182917

    Hepatitis B in St Petersburg, Russia (1994-1999): incidence, prevalence and force of infection.

    Beutels P; Shkedy Z; Mukomolov S; Aerts M; Shargorodskaya E

    Journal of Viral Hepatitis. 2003 Mar; 10(2):141-149.

    Hepatitis B (HB) is thought to be an expanding health problem in Russia. The incidence of infection was estimated from mandatorily reported HB cases in St Petersburg. The two-sided t-test for independent samples and the LOESS (locally-weighted regression) smoother were used to compare the age at infection for symptomatic, asymptomatic and chronic infections, by gender. The force of infection was estimated from seroprevalence data (907 sera taken in 1999) using a newly developed nonparametric method based on local polynomials, as well as an earlier method based on isotonic regression and kernel smoothers. With the local polynomial method, pointwise confidence intervals (95%) were constructed by bootstrapping. On average, men contracted HB infection at a significantly younger age than women (in 1999, 21.8 vs 22.7 years, respectively). The overall male to female ratio was 1.92. In 1999 the overall incidence almost doubled compared with the preceding years and tripled among the age groups with highest incidence (15–29-year olds: 85% of cases in 1999). The incidence increase was associated with a lower average age at infection (24.1 years in 1994 vs 22.1 years in 1999). The age and gender-specific force of infection estimates generally confirmed the incidence estimates and emphasized the usefulness of local polynomials to do this. Hence HB transmission in St Petersburg occurs mainly in young adults. The dramatic increase of infections in 1999 was probably due to injecting drug use. Without intervention, HB virus is expected to continue to spread rapidly with a greater proportion of female infections caused by sexual transmission. These trends may also provide an indication for HIV transmission. (author's)
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  4. 4
    781193

    Conditions of fertility decline in developing countries, 1965-75.

    MAULDIN WP; BERELSON B; SYKES Z

    Studies in Family Planning. 1978 May; 9(5):89-147.

    A macroanalysis of the correlates of fertility decline in developing countries for the period 1965-75. The analysis focuses on how much of the fertility decline is associated with socioeconomic variables such as health, education, economic status, and urbanization, or with "modernization" as a whole, and how much with population policies and programs designed to reduce rates of growth. The data are examined in a variety of ways: 1) simple correlations among the variables; 2) multiple regression analysis using both 1970 values of socioeconomic variables and, for the alternative lag theory, 1960 values; 3) change in the socioeconomic variables over time; 4) a special form of regression analysis called path analysis; 5) a relatively new type of analysis called exploratory data analysis; 6) relation of socioeconomic level and program efforts to both absolute and percentage declines in fertility; 7) crosstabulations of program effort with an index of socioeconomic variables. Such data and analyses show that the level of "modernization" as reflected by 7 socioeconomic factors has a substantial relationship to fertility decline, but also that family planning programs have a significant, independent effect over and above the effect of socioeconomic factors. The key finding probably is that 2 (social setting and program effort) go together most effectively. Countries that rank well on socioeconomic variables and also make substantial program effort have had on average much more fertility decline than have countries with one or the other, and far more than those with neither. Finally, the relationship between predicted and observed crude birth rate decline for the 94 developing countries over this period is illustrated for different combinations of actors, and an attempt is made to estimate the quantitative impact of the major conditions upon the intermediate variables traditionally assumed to account for crude birth rate change.(AUTHOR ABSTRACT)
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