A tuberculin skin test survey among Afghan children in Kabul.

SETTING: Kabul, Afghanistan, October to November 2000. OBJECTIVE: To determine the prevalence and the average annual risk of infection with Mycobacterium tuberculosis (ARTI). METHODS: A cluster sampling method was selected to carry out the survey. Sub-divisions of Kabul's districts were chosen, and door-to-door visits were carried out to register the children. The prevalence of tuberculous infection was determined using a cut-off point to denote infection and mixture analysis. The average ARTI was derived algebraically from the prevalence estimates. RESULTS: The tuberculin skin test was administered and read in 89% of registered children. Utilising a cut-off point of > or = 8 mm in duration, the estimated prevalence of tuberculous infection was 4.3% and the calculated average ARTI was 0.61%. Using mixture analysis, the average ARTI was estimated to be 0.34% (95% credibility interval 0.23-0.54). This indicates a substantial decrease from the estimated ARTI of 2.55% calculated in the 1963 survey. CONCLUSIONS: There has been a large decrease in the risk of tuberculous infection in Kabul since the last assessment. The adverse situation in the past decades does not appear to have severely affected the epidemiological situation.

Trends in the prevalence of infection with mycobacterium tuberculosis in Korea from 1965 to 1995: an analysis of seven surveys by mixture models.

SETTING: Korea. OBJECTIVE: Estimation of the prevalence of tuberculous infection from tuberculin skin test surveys can be difficult if cross-reactions resulting from infection with environmental mycobacteria outweigh reactions resulting from tuberculous infection. Mixture analysis was thus chosen as a novel approach for estimating the prevalence of tuberculous infection in Korea. DESIGN: Seven tuberculin skin test surveys conducted between 1965 and 1995 were analyzed by mixture models, a statistical methodology used either to estimate a prevalence or to classify individuals into predefined homogeneous sub-populations. A Bayesian approach including prior information on component distributions was taken. The final model was selected based on the fit to observed values, and the analysis was therefore stratified by sex and year of survey and included age as a covariate. RESULTS: The results showed a large decrease in tuberculous infection in the population below 30 years of age: among 10- to 14-year-old boys (girls), infection prevalence decreased from 74.5% (67.9%) in 1965 to 16.5% (16.9%) in 1995. Additionally, the mean induration for individuals with tuberculous infection decreased by 2mm between 1965 and 1995, indicating a changing sensitivity of tuberculin over time. CONCLUSIONS: Mixture analysis is a promising approach for determining the prevalence of tuberculous infection in the presence of substantial interference from infection with environmental mycobacteria and changing tuberculin reaction sizes over time.

HIV testing and retesting for men and women in Switzerland.

This study was conducted to describe voluntary HIV testing in the general population in Switzerland and to estimate yearly HIV test incidence. In 1994, a representative telephone survey of individuals aged 17 to 45 years obtained self-reported information on HIV testing. In addition to describing cumulative HIV test incidence, yearly HIV test incidence over time was estimated by a Bayesian hurdle model allowing for the plausible scenario of test consumption differing between first test and subsequent retests. Overall, 33% of the Swiss population (age 17 to 45 years) has been tested at some time for HIV on a voluntary basis (30% men, 36% women). For the time period 1990-1994, the result showed for 35-year-old individuals with supposedly low risk behavior, that 1) annual test incidence (first test or retest) showed a greater increase for men (4.2 to 5.9%) than for women (5.0 to 6.0%); 2) annual first test incidence increased moderately and differed for men and women (2.9 to 3.4% for men, 4.6 to 5.2% for women), and 3) annual retest incidence was twice as high for men (17.6%) as for women (8.6%). In conclusion, a substantial part of the Swiss population has been tested at some stage for HIV on a voluntary basis, and differences exist for testing and retesting between men and women.

Study of the dog population and the rabies control activities in the Mirigama area of Sri Lanka.

The national health authorities of Sri Lanka have adopted a combined strategy of rabies vaccination and stray dog removal to control endemic dog rabies. Despite the control efforts, an increase of animal and human rabies cases has occurred since 1994. As a consequence, a project to evaluate the national rabies control program has been started and a study focussing on the dog population and rabies control activities in a limited area of Mirigama was conducted. Information on canine abundance and the accessibility of dogs for rabies vaccination was obtained by a household survey, vaccination of dogs against rabies at several vaccination points, collar-marking, and transect line recapture. The number of unvaccinated dogs was estimated by using Bayesian methodology. The estimated number of dogs per square kilometre was 87 (95% credibility interval: 80, 93) for owned dogs and 108 (100, 116) for owned and ownerless dogs. Coverage after the immunisation campaign was 57.6% (53.3, 61.9%) if vaccination at the vaccination points was considered and 66% (60.4, 72.0%) if recently provided vaccination by private veterinarians was also taken into account. The proportion of households with at least one dog vaccinated varied between 59.1 and 94.2% within the catchment area of the different vaccination points. Unvaccinated dogs were puppies (12%), ownerless dogs (57%), and owned dogs, which were not presented for vaccination (31%). In order to improve the rabies immunisation coverage among dogs and to achieve complete elimination of rabies it was recommended that the 95% catchment area of each vaccination point be assessed, the distribution of vaccination points in the vaccination area be redefined if necessary, a system for the vaccination of dogs missing the vaccination campaign for dog owner-specific reasons be established, and an inexpensive marking system be used for vaccinated dogs.

Adjusting AIDS incidence for non-stationary reporting delays: a necessity for country comparisons.

In many industrialized countries, infection with the human immunodeficiency virus (HIV) is one of the leading causes of mortality in adult persons below age 45. The incidence of the acquired immunodeficiency syndrome (AIDS) from surveillance systems is the most common indicator to compare the situation of the HIV-epidemic in different geographic regions or countries. Due to reporting delays, AIDS diagnoses in recent years are incompletely reported and need to be estimated. In this study, we analyze reporting delays in Switzerland and Spain for the period from 1988 to mid-1995 and estimate the number of AIDS diagnoses per year. A descriptive analysis for Switzerland shows increasing reporting delays in recent years. Then, a Bayesian generalized linear model on reverse-time hazards is used to model time trends of the reporting delay distribution. The model shows that in recent years (i) for Switzerland reporting delays became longer and yearly AIDS incidence might continue to increase, and (ii) for Spain, reporting delays became considerably shorter resulting in too large estimates of yearly AIDS incidence if stationarity of reporting delays is assumed. Critical issues of modeling non-stationarity of the reporting system are discussed and it is emphasized that estimates of recent AIDS incidence can be biased significantly if time trends of reporting are ignored-as in the example of Switzerland and Spain, this may severely distort comparisons of the AIDS epidemic in different countries.

Field evaluation of two bait delivery systems for the oral immunization of dogs against rabies in Tunisia.

Two bait delivery systems for the oral immunization of dogs against rabies were tested in small scale field trials in a semi-rural area in Tunisia: bait delivery to owned dogs during door to door visits of households (door to door baiting) and distribution of baits on transect lines (transect line baiting). A prototype bait (DBL2) configured for industrial production and containing either sulfadimethoxine (SDM) as a systemic marker or Rhodamine B as a topical marker was used. The overall proportion of dogs which took a bait and presented topical marker staining after door to door baiting was 59.1%. The total time and costs spent per bait accepting dog averaged 34 person minutes and US$4, respectively. Unconsummated baits were readily recovered. No unprotected human contacts with baits were recorded. Door to door baiting is a very specific but time-consuming method that enables a safe administration of vaccine baits to owned dogs. For transect line baiting, baits were distributed at a density of ca 3000 baits per km2 along double transect lines. Baits were recovered after 20 h. According to the proportion of SDM positive serum samples, 24.1% of owned dogs in the baiting area had consumed baits. Of all owned and ownerless dogs, presumably free-roaming during transect line baiting, > 40% had consumed baits. The total time and costs spent per bait accepting dog averaged 48 person minutes and ca US$20, respectively. The household census revealed 32 direct human contacts with the bait matrix which corresponds to 1.4% of inhabitants. Placing baits on transect lines gives the possibility to vaccinate dogs not accessible by vaccination systems which base on dog owner participation. However, the method is not specific, less safe than other systems, not easily accepted by the human population, and costly.

Methodologic challenges of randomized controlled studies on in-home comprehensive geriatric assessment: the EIGER project. Evaluation of In-Home Geriatric Health Visits in Elderly Residents.

Previous controlled studies have shown that preventive home visits are a promising method for disability prevention in elderly persons; however, due to the lack of data on cost effectiveness and optimal intervention methods, there is still debate on their usefulness. Therefore, additional controlled studies must use new methods to resolve these unanswered issues. We present a novel approach used in the project EIGER (Evaluation of In-Home Geriatric Health Visits in Elderly Residents), an ongoing randomized controlled trial of preventive home visits in community-residing persons aged 75 years and older in Bern, Switzerland. The intervention consists of in-home visits with structured comprehensive geriatric assessment and follow-up by specially trained nurses who collaborate with geriatricians and an interdisciplinary team. Special methods were used to optimize the sample size, to improve the health care cost analysis, to minimize and explore refusal to participate, to apply stratified randomization for subgroup analysis, and to evaluate the intervention process with a tracer method. Selected baseline findings (N = 791, mean age 82 years, 73% female) include uncontrolled systolic hypertension (54%), balance/gait disorder (9%), cognitive impairment (7%), 6 or more medications (21%), depressive symptoms (10%), and impaired basic ADL (15%). Baseline findings demonstrate that this study is likely to contribute to some of the unresolved issues of in-home prevention for older persons.