Bayesian analysis of an epidemiologic model of Plasmodium falciparum malaria infection in Ndiop, Senegal.

Plasmodium falciparum has a complex transmission cycle. Public health planning and research would benefit from the ability of a calibrated model to predict the epidemiologic characteristics of populations living in areas of malaria endemicity. This paper describes the application of Bayesian calibration to a malaria transmission model using longitudinal data gathered from 176 subjects in Ndiop, Senegal, from July 1, 1993, to July 31, 1994. The model was able to adequately predict P. falciparum parasitemia prevalence in the study population. Further insight into the dynamics of malaria in Ndiop was provided. During the dry season, the estimated fraction of nonimmune subjects goes down to 20% and then increases up to 80%. The model-predicted time-weighted average incidences contributed by nonimmune and immune individuals are 0.52 cases per day and 0.47 cases per day, respectively. The median times needed to acquire infection (conversion delay) for nonimmune and immune individuals are estimated at 39 days and 285 days, respectively.

Screening blood donations for hepatitis C in Central Africa: analysis of a risk- and cost-based decision tree.

Four screening strategies (no testing, HC Abbott, HC Pasteur, and a combined test) for the detection of hepatitis C virus (HCV) antibody in donated blood were considered in a formal decision tree. Decision criteria included residual risk of infection and overall monetary cost. Tree parameters were determined using data from the Central African Republic. The prevalences observed among blood donors for HIV infection, hepatitis B, syphilis, and hepatitis C varied between 6% and 15%. The current residual risk of transfusion-transmitted infections is very high (8.4%). Screening for HCV would bring that risk down to about 3% with either the HC Pasteur, the HC Abbott, or the combined test. Even though baseline analysis gives preference to the HC Abbott test (the combined test coming out last), Monte Carlo sensitivity and uncertainty analyses showed that Abbott's and Pasteur's tests are interchangeable, on the basis or either risk or cost considerations.

High prevalence in Central Africa of blood donors who are potentially infectious for human herpesvirus 8.

BACKGROUND: In western countries, the transmission of human herpesvirus 8 (HHV-8) via blood transfusion has been recently postulated. In sub-Saharan African, the incidence of HHV-8-associated Kaposi's sarcoma and the seroprevalence for HHV-8 in autochthonous populations are high. STUDY DESIGN AND METHODS: The aim of this study was to estimate the prevalence of blood donations potentially infectious for HHV-8 in the general adult population of Central Africa. Forty-nine blood donors at the Centre de Transfusion Sanguine in Bangui, the capital of the Central African Republic, were selected. Forty-five inpatients of Broussais Hospital, Paris, France, who were known to be seronegative for HIV and hepatitis B and C viruses and who had not received heart or kidney transplants, were chosen as a European "control" group for comparison. HHV-8 DNA sequences were detected in peripheral blood mononuclear cells by nested polymerase chain reaction using primer sets located in the HHV-8 open reading frame 26. RESULTS: Eleven (22.5%; 95% CI: 12%-37%) of 49 blood donors were positive for HHV-8. Three (6%) were HIV-1 seropositive. Two (67%) of the 3 HIV-infected blood donors were also positive for HHV-8. All blood donors were apparently healthy; none was known to suffer from Kaposi's sarcoma. Only one (2.2%) control was carrying HHV-8 DNA on the peripheral blood mononuclear cells. The prevalence of HHV-8 was higher in blood donors from Bangui than in patients from Broussais Hospital. CONCLUSIONS: HHV-8 infection is highly prevalent in an apparently healthy adult population from Central Africa, which raises concerns about HHV-8 transmission through transfusion in this setting.

Cervicovaginal anti-HIV antibodies in index women from HIV-discordant, exclusively heterosexual, couples.

Cervicovaginal IgA and IgG anti-gp160 antibodies were evaluated in cervicovaginal secretions from twelve HIV-discordant heterosexual couples, matched with twelve HIV-concordant heterosexual couples, at similar stage of HIV disease. The mean reciprocal end-point titers of cervicovaginal IgA or IgG to gp160 were similar in cases and in controls. These observations suggest that cervicovaginal antibodies to HIV do not appear as biological indicators sufficiently relevant to explain a possible reduced infectivity of the female index case in HIV-discordant couples, by comparison with HIV-concordant couples.

World Health Organization clinical case definition for AIDS in Africa: an analysis of evaluations.

In 1985 at a World Health Organization (WHO) workshop on AIDS in Bangui, Central African Republic, a clinical case definition of Acquired Immune Deficiency Syndrome (AIDS) was developed for developing countries, such as sub-Saharan Africa, where sophisticated diagnostic equipment is not widely available. A particular cachectic syndrome, the "slim disease", which is highly suggestive of AIDS in Africa, constitutes the substratum for the clinical definition for AIDS. The WHO/Bangui definition in adults has a sensitivity of 60%, a specificity of 90%, and a high predictive value especially in endemic areas. The WHO/Bangui clinical case definition for paediatric AIDS is less easy to use in practice. Its low sensitivity (about 35%) is in relation to its incapacity to diagnose many of the frequently observed secondary infection for paediatric AIDS according to the CDC criteria. The WHO/Bangui clinical definition for AIDS seems to be convenient for epidemiological surveillance of the HIV epidemic in Africa. Nevertheless, the low sensitivity and the low specificity result in the failure to detect some cases of full blown AIDS.

PIP: In 1985, at a WHO workshop on AIDS in Bangui, Central African Republic, a clinical case definition of AIDS was developed for developing countries. This 1st definition contained 4 major criteria (chronic asthenia, major weight loss, chronic fever, and chronic diarrhea) and 6 minor criteria (chronic cough, persistent lymphadenopathy, herpes zoster, recurrent herpetic infection, pruritic dermatitis, and oropharyngeal candidiasis). Kaposi's sarcoma and cryptococcal meningitis were sufficient by themselves for the diagnosis of AIDS. In children, the temporary definition of AIDS consisted of 3 major clinical criteria (weight loss and/or abnormally slow growth, chronic diarrhea lasting more than 1 month, and fever lasting more than 1 month), and 6 secondary clinical criteria (generalized lymphadenopathy, oropharyngeal candidiasis, repeated common infections such as otitis and pharyngitis, persistent cough, generalized pruritic dermatitis, and confirmed maternal HIV infection). The revised Bangui definition was evaluated in 174 adult patients hospitalized at the Mama Yemo Hospital of Kinshasa, Zaire. 46% of 174 patients met the criteria of the WHO/Bangui definition. Overall, the sensitivity of the definition for HIV-1 infection was 59%, the specificity was 90%, and the positive predictive value (PPV) was 74%. However, the clinical case definition of African AIDS lacks specificity when it is applied to patients suffering from cachectic syndromes. The Bangui definition was also evaluated at the pediatric ward of Mama Yemo Hospital with 159 hospitalized children whose mean age was 33 months. 21 (13%) were infected by HIV-1. The sensitivity of the definition was 35%, its specificity was 86%, and its PPV was 26%. Although the specificity was relatively high, the low values of sensitivity and PPV underline the weakness of the Bangui clinical case definition for diagnosing pediatric AIDS cases.