PubMed Health⌕ Search

Biomedical subjects

M Zwahlen

Publications and source records attributed to M Zwahlen.

At least 19 recordsLinked to original sources
PubMed2001

HIV and hepatitis virus infections among injecting drug users in a medically controlled heroin prescription programme.

BACKGROUND: In Switzerland, 1,035 patients were accepted for admission to the medically controlled prescription of narcotics programme (PROVE) from 1 January 1994 until 31 December 1996. Heroin, methadone, and morphine were prescribed. This paper presents the prevalence and incidence of HIV and hepatitis B/C infections in the sociomedical context of the participants. METHODS: Admission criteria were a minimum age of 20 years, at least a two-year duration of daily heroin consumption, a negative outcome of at least two previous treatments, and documented social and health deficits as a consequence of their heroin dependence. The patients were examined at admission and every six months. A serological test was carried out at the same time for HIV and hepatitis B/C. RESULTS: Serological testing on admission could be performed in more than 80% of the entrants and documented a very high seroprevalence of antibodies against HBcore (73%) and HCV (82%). The prevalence of HIV and hepatitis B/C increased with duration of drug intake. In the follow-up analysis of seronegative individuals, a halving of the risk of viral hepatitis infection was shown when comparing the first six months with the period greater then six months after PROVE entry. CONCLUSION: The tests conducted showed high prevalence and incidence rates of HIV and hepatitis B/C among patients who had consumed intravenous drugs for years. The descriptive analysis in heroin-assisted treatment showed a reduction in infection risk for viral hepatitis corresponding to the lower risk behaviour of patients.

Adult↗
PubMed2000

[Herpes simplex virus type 1 and 2 in Switzerland].

A worldwide increase in the incidence of genital herpes infections has been described in recent years. Transmission of the herpes simplex virus type 2 (HSV-2) by asymptomatic seropositive subjects is considered to be a relevant mode of infection. The seroprevalence of HSV-2 varies considerably between different populations. In Europe, data are scarce and the epidemiological situation in Switzerland is unknown. In 1997 we performed serological examinations in 151 adult volunteers (87% between 20 and 49 years of age) of a low-risk population from the region of Basel with no history of genital herpes or any other sexually transmitted disease. The overall seroprevalence of HSV-1 was 77% and an annual seroconversion rate of 4.6% (95% CI: 3.8-5.6) was estimated for both sexes. Of the 51 subjects with no symptoms of orolabial herpes, 25 (49%) proved to be HSV-1 seropositive. In contrast, of 91 patients with symptoms of orolabial herpes, 90 (97%) had serum antibodies against HSV-1. The seroprevalence of HSV-2 was 14.6% for women (n = 89) and 8.1% for men (n = 62). The annual seroconversion rate was estimated to be 0.61% (95% CI: 0.14-1.4) for women and 0.49% (95% CI: 0.09-1.4) for men for the period after 1985 (when "safer sex" and the use of condoms were promoted). Our results indicate the significance of herpes simplex virus type 2 infections in Switzerland. More detailed studies are needed to describe the epidemiology of HSV-2 infections more reliably, especially in view of progress in the development of vaccines against HSV infections.

Adult↗
PubMed2000

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.

Adolescent↗
PubMed2000

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.

Adolescent↗
PubMed1999

High frequency of non-B subtypes in newly diagnosed HIV-1 infections in Switzerland.

HIV-1 subtypes were determined in newly diagnosed residents of Switzerland. Blood was anonymously collected from patients with a first confirmed positive HIV-1 test result. Viral DNA from the env V3-V5 region was amplified by nested polymerase chain reaction (PCR) and screened for subtype B by heteroduplex mobility assay. All amplicons not identified as B were sequenced. From November 1996 to February 1998, 206 samples were analyzed. Main transmission risks were unprotected heterosexual (55.7%) or homosexual (27.1%) sexual contact or intravenous drug use (12.9%). Subtype B dominated in patients of Swiss, other European, American, or Asian citizenship; particularly high frequencies were found in homosexuals (97%) and drug users (94%). Non-B subtypes including A, C, D, E, F, G, H, a possible B/F recombinant, and a sequence related to J were present in 28.2% (95% confidence interval [CI], 22.9%-35.0%). Non-B were frequent in African citizens (95%), heterosexually infected individuals (44%), and women (43%). Heterosexually infected Swiss males harbored non-B strains in 18% and females in 33%. The results document a change in the epidemiology of newly diagnosed HIV-1 infections in Switzerland: predominance of heterosexual transmission and a high frequency of non-B subtypes.

Adult↗
PubMed1999

The Swiss Network of Dermatology Policlinics HIV prevalence study: rationale, characteristics and results (1990-1996).

The Swiss Network of Dermatology Policlinics (SNDP) has monitored the prevalence of HIV among patients treated for a sexually transmitted disease (STD) since January 1990. A questionnaire was sent to each policlinic in the network (Basel, Bern, Geneva, Lausanne, and two in Zurich) to collect information on their participation in this study and the characteristics of the network. The responses reveal that the six policlinics followed the HIV prevalence study protocol in a uniform manner and had similar logistical and organisational characteristics HIV prevalences in this population were high (1.6% among heterosexuals, 24.0% among male homo/bisexuals, and 35.7% among injecting drug users), have remained stable, and vary considerably by policlinic. In conclusion, we found that the policlinics have correctly implemented the HIV prevalence study and that the SNDP is a homogeneous sentinel surveillance system. Knowledge of the organisation and characteristics of the SNDP has allowed us to better interpret and present our data, and we recommend that other sentinel surveillance systems of this type collect this sort of information.

Ambulatory Care Facilities↗
PubMed1998

Mortality from respiratory tuberculosis in Switzerland.

Since 1901, the Swiss Federal Office of Statistics has published at least each decade detailed mortality statistics from tuberculosis. These cross-sectional data on deaths from respiratory tuberculosis from 1901 to 1991 were utilized to analyse retrospectively tuberculosis death experience within each birth cohort. The cross-sectional data indicate that tuberculosis mortality increases with age in each successive decade. Nevertheless, the cohort-contour approach indicates that this phenomenon is the result of a much higher mortality that each cohort experienced in their early adulthood, and that mortality form respiratory tuberculosis in Switzerland always preferentially affected the young. The data also indicate that tuberculosis mortality in Switzerland has been decreasing for at least 160 years, and perhaps peaked as early as in the eighteenth century.

Adolescent↗
PubMed1998

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.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Voluntary confidential HIV testing of STD patients in Switzerland, 1990-5: HIV test refusers cause different biases on HIV prevalences in heterosexuals and homo/bisexuals. Swiss Network of Dermatovenereology Policlinics.

OBJECTIVES: To monitor the prevalence of HIV infection among heterosexual and male homo/bisexual STD patients and assess the effect of HIV test refusers on the HIV prevalences. METHODS: A voluntary confidential HIV test was offered to all people diagnosed with an STD at the Swiss Network of Dermatovenerology Policlinics (SNDP) between July 1990 and June 1995. Anonymous sociodemographic and behavioural information was collected for each patient regardless of whether s/he accepted or refused the HIV test. RESULTS: The prevalence of HIV was 1.6% among heterosexuals and 22.4% homo/bisexual men and remained stable between July 1990 and June 1995. Refusal rates were 17.5% among heterosexuals and 16.0% among homo/bisexual men and did not change significantly over time. To assess the potential effect of HIV test refusers on the monitored HIV prevalences, we analysed test refusers by multivariate logistic regression. Among heterosexuals, refusal rates were significantly higher among patients with relatively low risk behaviours (patients reporting 0-1 sexual partners in the previous 6 months) while among homo/bisexual men they were significantly higher in those with high risk behaviours (patients reporting 10 or more sexual partners in the previous 6 months). CONCLUSIONS: We found high and stable HIV prevalences among patients treated for an STD at the SNDP. It appears that HIV test refusers biased HIV prevalences among heterosexuals and homo/bisexual men in different directions: in heterosexuals HIV prevalences were overestimated and in homo/bisexuals they were underestimated. A regular analysis of the characteristics of HIV test refusers should be an integral part of surveillance systems which use voluntary confidential HIV testing.

Bias↗
PubMed1995

[The extent of transfusion-associated HIV infections in Switzerland until 1994: an updated estimate].

OBJECTIVE: The first report on transfusion-associated HIV infections was published in the USA in 1982. The first case reports in Switzerland were published in 1986. So far there has never been a methodologically sound answer to the question of how many persons were infected with HIV by receiving transfusions in Switzerland before the introduction of universal HIV blood donor screening. METHODS: The following available data sources were analyzed simultaneously: firstly, the results of the look-back study conducted in 1993, secondly, the reports of HIV infections and AIDS cases in the national surveillance system, and, thirdly, the claims for compensation for HIV-infected transfusion recipients and hemophiliacs. Two methodologically different and independent estimates were obtained. Firstly, the coverage of the look-back study was estimated, which made it possible to calculate the total number of documentable transfusion-associated HIV infections in Switzerland. Secondly, matching was performed on the cases in the look-back study and the reports in the national surveillance system. Applying formulas of capture-recapture designs provided a second estimate of the total number of documentable transfusion-associated HIV infections. The claims for compensation were used to corroborate the estimates obtained. RESULTS: The two methods produced almost identical figures which were corroborated by the number of claims for compensation. It is therefore estimated that 80 to 100 persons in Switzerland may have been diagnosed as having HIV infection because of transfusions in Switzerland in the years after 1980. The last five known infections occurred in 1986 (four) and, after termination of the look-back study, in 1994 (one). However, the estimate of 80 to 100 does not include individuals who were infected before 1986 and died soon--within weeks or a few months--after the transfusion without diagnosis of HIV infection being possible. CONCLUSION: This estimate of the total number of transfusion-associated HIV infections in Switzerland is approximately half earlier published ones. In addition, the present study will probably reduce the remaining uncertainties about the size of these iatrogenic HIV infections in the 1980s.

Blood Component Transfusion↗
PubMed1995

Impact of the change from an injectable to a fully oral regimen on patient adherence to ambulatory tuberculosis treatment in Dar es Salaam, Tanzania.

OBJECTIVE: To measure the impact on patient adherence to directly observed ambulatory tuberculosis treatment substituting an all-oral treatment regimen for a regimen containing streptomycin. METHODS: The expected and observed attendance of patients during the intensive phase of anti-tuberculosis treatment was measured daily at two out-patient clinics in Dar es Salaam. During the observation period, treatment was changed from a regimen containing streptomycin to an all-oral regimen, and attendance proportions were compared for the three periods during which patients always, sometimes or never received streptomycin during the intensive phase of treatment. RESULTS: In Kinondoni, an average of 98 patients was expected every day, in Ilala 127. No significant difference was observed in attendance in Kinondoni between periods when patients always (median attendance 95.9%) and never (median 95.7%) received streptomycin injections as part of their intensive phase treatment for tuberculosis. In Ilala, no difference was noted in attendance between the period in which patients received streptomycin for at least part of their treatment (median 91.3%) and the period when ethambutol had fully replaced streptomycin (median 91.8%). CONCLUSIONS: In these two districts of Dar es Salaam, patient adherence to a completely oral treatment regimen was indistinguishable from that to a streptomycin-containing regimen. Given the potential of iatrogenic transmission of HIV and the advantages in reduced staff time and drug costs, the results clearly justify the replacement of streptomycin with ethambutol in Tanzania for new patients receiving an ambulatory rifampicin-containing regimen.

Administration, Oral↗