Estimating the number of probable new SARS-CoV-2 infections among tested subjects from the number of confirmed cases.

OBJECTIVES: In most African countries, confirmed COVID-19 case counts underestimate the number of new SARS-CoV-2 infection cases. We propose a multiplying factor to approximate the number of biologically probable new infections from the number of confirmed cases. METHODS: Each of the first thousand suspect (or alert) cases recorded in South Kivu (DRC) between 29 March and 29 November 2020 underwent a RT-PCR test and an IgM and IgG serology. A latent class model and a Bayesian inference method were used to estimate (i) the incidence proportion of SARS-CoV-2 infection using RT-PCR and IgM test results, (ii) the prevalence using RT-PCR, IgM and IgG test results; and, (iii) the multiplying factor (ratio of the incidence proportion on the proportion of confirmed -RT-PCR+- cases). RESULTS: Among 933 alert cases with complete data, 218 (23%) were RT-PCR+; 434 (47%) IgM+; 464 (~ 50%) RT-PCR+, IgM+, or both; and 647 (69%) either IgG + or IgM+. The incidence proportion of SARS-CoV-2 infection was estimated at 58% (95% credibility interval: 51.8-64), its prevalence at 72.83% (65.68-77.89), and the multiplying factor at 2.42 (1.95-3.01). CONCLUSIONS: In monitoring the pandemic dynamics, the number of biologically probable cases is also useful. The multiplying factor helps approximating it.

The HIV cascade of care among serodiscordant couples in four high HIV prevalence settings in sub-Saharan Africa.

BACKGROUND:  HIV-serodiscordant couples are at high risk of HIV transmission. In sub-Saharan Africa, HIV-serodiscordant couples contribute ~30% of all new infections in the region. OBJECTIVES: To quantify the prevalence of HIV-serodiscordant couples and evaluate steps of the HIV cascade of care among people living with HIV in serodiscordant relationships in four high-prevalence settings in sub-Saharan Africa. METHODS:  Four HIV prevalence surveys were conducted: in Ndhiwa (Kenya) in 2012, in Chiradzulu (Malawi) in 2013, and in Gutu (Zimbabwe) and Nsanje (Malawi) in 2016. Eligible individuals aged 15 - 59 years were asked to participate in voluntary rapid HIV testing. Viral load and CD4 counts were measured on those who tested HIV-positive. A couple was defined as a man and a woman who reported being married or cohabiting and were living together in the same household. RESULTS: Among 4 385 couples, the prevalence of HIV serodiscordancy was 10.9% (95% confidence interval (CI) 10.2 - 11.5) overall, ranging from 6.7% (95% CI 5.6 - 7.9) in Nsanje to 15.8% (95% CI 14.5 - 17.3) in Ndhiwa. Men were the HIV-positive partner in 62.7% of the serodiscordant couples in Ndhiwa, in 60.4% in Gutu, in 48.8% in Chiradzulu and in 50.9% in Nsanje. Status awareness among HIV-positive partners in serodiscordant couples ranged from 45.4% in Ndhiwa to 70.7% in Gutu. Viral load suppression (VLS) ranged from 33.9% in Ndhiwa to 68.5% in Nsanje. VLS was similar by sex in three settings, Ndhiwa (37.8% (men) v. 27.8% (women); p=0.16), Nsanje (60.7% v. 76.9%; p=0.21) and Gutu (48.2% v. 55.6%; p=0.63), and dissimilar by sex in Chiradzulu (44.4% v. 62.7%; p=0.03). CONCLUSIONS: Low HIV status awareness and poor VLS among HIV-positive partners are major gaps in preventing transmission among serodiscordant couples. Intensifying programmes that target couples to test for HIV and timely antiretroviral therapy initiation could increase VLS and reduce HIV transmission.

Factors associated with HIV status awareness and Linkage to Care following home based testing in rural Malawi.

OBJECTIVE: HIV diagnosis and linkage to care are the main barriers in Africa to achieving the UNAIDS 90-90-90 targets. We assessed HIV-positive status awareness and linkage to care among survey participants in Chiradzulu District, Malawi. METHOD: Nested cohort study within a population-based survey of persons aged 15-59 years between February and May 2013. Participants were interviewed and tested for HIV (and CD4 if found HIV-positive) in their homes. Multivariable regression was used to determine factors associated with HIV-positive status awareness prior to the survey and subsequent linkage to care. RESULTS: Of 8277 individuals eligible for the survey, 7270 (87.8%) participated and were tested for HIV. The overall HIV prevalence was 17.0%. Among HIV-positive participants, 77.0% knew their status and 72.8% were in care. Women (adjusted odds ratio [aOR] 6.5, 95% CI 3.2-13.1) and older participants (40-59 vs. 15-29 years, aOR 10.1, 95% CI 4.0-25.9) were more likely to be aware of their positive status. Of those newly diagnosed, 47.5% were linked to care within 3 months. Linkage to care was higher among older participants (40-59 vs. 15-29, adjusted hazard ratio [aHR] 3.39, 95% CI 1.83-6.26), women (aHR 1.73, 95% CI 1.12-2.67) and those eligible for ART (aHR 1.61, 95% CI 1.03-2.52). CONCLUSIONS: In settings with high levels of HIV awareness, home-based testing remains an efficient strategy to diagnose and link to care. Men were less likely to be diagnosed, and when diagnosed to link to care, underscoring the need for a gender focus in order to achieve the 90-90-90 targets.

[Revival after Ebola: multidisciplinary assessment at 1 year, prospect and follow-up study of surviving patients from Ebola in Guinea (PostEboGui cohort)]. / (Re)vivre après Ebola : bilan à un an et perspectives d'une étude d'évaluation et accompagnement des patients déclarés guéris d'une infection par le virus Ebola en Guinée (cohorte PostEboGui).

Ebola virus disease (EVD) epidemic that spread in West Africa from the end of 2013 to early 2016 has reached more people than all past epidemics. Beyond care management of acute phase ill patients and measures for the control of the epidemic, the outcome of Ebola survivors became an important question as their number increased and raised new issues. A multidisciplinary prospective cohort of survivors in Guinea has been launched by IRD UMI 233 and Donka National Hospital, Conakry, Guinea, to assess the long-term clinical, psychological, sociological, immunological, and viral outcomes potentially related to EVD. This paper describes PostEboGui Programme, constraints and changes to the initial proposal, participants, first results, and new issues, 1 year after its start, in a descriptive and critical view. We started also to work on ethical aspects in the context of epidemics and of mass interventions with a risk of overinvestigation of patients.

[Buruli ulcers: an advocacy agenda to improve its control]. / Ulcère de Buruli : construction d'un agenda de plaidoyer pour améliorer la lutte.

Doctors Without Borders (Médecins Sans Frontières) has developed an advocacy agenda in Cameroon to better meet its patients' needs and to simplify control of Buruli ulcers. This agenda is based on 4 priorities: diagnostic (development of a clinical score), chemotherapeutic (to envision drug administration at home, without daily hospital visits), dressings, and HIV coinfection. These priority objectives should make it possible to reduce the duration of hospitalization and limit the need for surgery.

[Differential diagnoses of infection with Mycobacterium ulcerans: case reports from Akonolinga, Cameroon]. / Diagnostics différentiels de l'infection à Mycobacterium ulcerans : cas cliniques d'Akonolinga, Cameroun.

The authors describe the results of a program for the management of Buruli ulcers in Akonolinga (Cameroon). Its principal objective is to improve the diagnosis of dermatologic lesions and thereby to improve the indications for specific antibiotic therapy. This study, conducted in February, 2013, included 271 patients. Differential diagnosis of suspicious lesions was best with diagnostic examinations completed by histologic examination of a punch biopsy sample and advice from expert dermatologists.

Adherence to antiretroviral therapy, virological response, and time to resistance in the Dakar cohort.

In 1998, with the launch of the Senegalese Initiative for Antiretroviral Access (ISAARV), Senegal became one of the first African countries to propose an antiretroviral access program. Our objective in this paper is to study the time to any first drug resistance, as well as predictors of the time to resistance. We propose a joint model to study the effect of adherence to the HAART therapy, and virological response on the time to resistance mutations. A logistic mixed model is used to model the time-dependent adherence process; and a Markov model is used to study the virological response. Given the presence of missing data in the adherence process and in the virological response, the latent adherence and virological states are then included in the linear predictor of the time to resistance model. The proposed time to resistance model takes into account interval-censored data as well as null hazard periods, during which the viral replication is very low. A Bayesian approach is used for accommodating with missing data and for prediction. We also propose model checking tools to study model adequacy.

Hepatitis B, C seroprevalence and delta viruses in HIV-1 Senegalese patients at HAART initiation (retrospective study).

The aim of this study was to determine hepatitis co-infection in a cohort of HIV infected patients at their inclusion in the Senegalese Initiative of ART Access. B, C, and D Hepatitis viruses serological markers were checked retrospectively on 363 stored plasma. For HBV, the Abbott laboratories equipment IMx was used to detect HBs Ag and anti Core Ab on negative HBs Ag samples. For HDV, anti Delta Ab was performed using the Abbott Murex Kit on all HBs Ag positive samples. For HCV, anti HCV Ab was detected by IMx as double screening test and confirmed by INNO-LIA(TM) HCV Core of Innogenetics laboratories. The statistical analysis was done with STATA V8. The study population was composed of 164 men and 199 women aged between 16 and 66 years. The immune and virological markers averages at their enrollment were 154 cell/mm(3) for TLCD4+ (n = 355 patients) and 4.9 log for viral load (n = 277 patients). HBs Ag was found in 61 patients or 16.8% and the prevalence of anti-HBc Ab was 83.2% (252/295). 2 patients or 3% on HBs Ag positive sample presents HBV/HDV co-infection Ab anti HCV was detects in 6 patients or 1.6% after confirmation and 2 patients had triple infection with HBV. These results showed that the prevalence of HBV and HCV in the population of persons living with HIV/AIDS in Senegal is similar to that found in the general population. Our data indicated that hepatitis pathology in the PLwHIV was essentially due to HBV. Further studies are needed to diagnose occult hepatitis in order to set up therapeutic strategies taking into account co-infections by hepatitis viruses in the ART programmes.

Impact of previous immunisation on the incidence of meningococcal disease during an outbreak in a Sahelian area of Senegal.

The occurrence of an outbreak of meningitis during three consecutive years in a study area under demographic and epidemiologic longitudinal surveillance allowed evaluating the impact of mass immunisation campaigns on the incidence of meningitis. During an outbreak of meningitis in the neighbouring region occurred 2 years before the first epidemic wave in the study area, 8 out of the 30 villages of the zone were immunised. The incidences of meningitis in these villages were compared with those of the villages that did not benefited from mass campaign. It appeared a very significant difference between the two groups of villages. More than a half of the cases of meningitis seemed to be avoided in the vaccinated villages compared to the others, suggesting that a previous immunisation limits the diffusion of the epidemic. After the second outbreak hit the study zone, a mass immunisation campaign concerned all the 30 villages. The incidences of meningitis were significantly different between villages according to the observed vaccine coverage. These results indicate that preventive immunisation could have a significant impact on meningitis outbreak diffusion.

[Analysis of evolution of vaccine coverage in Niakhar, a rural area of Senegal, between 1984 and 2003]. / Analyse de l'evolution de la couverture vaccinale a Niakhar, région rurale du Sénégal, entre 1984 et 2003.

In Senegal, the Expanded Programme of Immunization started by 1986 as a routine programme targeting 7 diseases: tuberculosis, tetanus, diphtheria, pertussis, poliomyelitis, measles and recently yellow fever Immunization against hepatitis B and Haemophilus influenzae b are proposed since 2005, but not implemented yet. In addition, there are mass immunization campaigns, such as National Immunization Day organized every year since 1999 against poliomyelitis and, in case of outbreak, against meningitis or yellow fever. In a 30,000 inhabitants rural study zone, vaccine contacts of children under 15 years of age are updated regularly several times a year since 1984. We also performed yearly cross sectional surveys from 1999 to estimate vaccine coverage in children of 24 months of age. Immunization status was assessed by vaccination cards presented by the children's parents and registers of health centres. We compared the results from both longitudinal and cross sectional surveys, which showed some differences. The last method seemed to indicate higher immunization rates. The vaccine coverage was slightly but not significantly higher in the study zone compared to the general vaccine coverage in Senegal, excepted for measles immunization for which the coverage was significantly lower in Niakhar. However results showed that interventions of all types lead to a high vaccine coverage (up to 80%) but are not sustainable. In the intervals, vaccine coverage decreased dramatically (below 40%), due mainly to irregular supply of antigens and poor accessibility of health facilities. Other factors are mentioned.

[Cluster sampling: consequences of data analysis on drawing conclusions]. / Le sondage en grappes: implications de la méthode d'analyse sur les conclusions de l'enquête.

BACKGROUND: Cluster sampling is commonly used since it does not require a sampling frame which lists all the individual enumeration units. However, this sampling design is often less precise than simple random sampling due to frequent homogeneity of individuals within clusters. This note illustrates that the precision of parameters such as mean, prevalence and odds ratio can be biased when the data analysis ignores the sampling design, yielding to possibly erroneous conclusions. METHODS: Data from a cluster sampling among clandestine sex workers in Senegal were used. Two analyses were performed and their results were compared. The first analysis took into account the sampling design (design-based analysis) while the second did not (naïve analysis). RESULTS: The range of confidence intervals in design-based analysis differed from -43% to +84% with regard to those of naive analysis, and different conclusions could be drawn. For instance, the human immunodeficiency virus (HIV) infection in clandestine sex workers was associated with condoms use and perceived risk of HIV infection in design-based analysis but not in naive analysis. CONCLUSION: The data analysis must take into account the sampling design, and this is facilitated by the availability of statistical software with survey analysis capabilities.

Maternal mortality and access to obstetric services in West Africa.

OBJECTIVES: Process evaluation has become the mainstay of safe motherhood evaluation in developing countries, yet the extent to which indicators measuring access to obstetric services at the population level reflect levels of maternal mortality is uncertain. In this study we examine the association between population indicators of access to obstetric care and levels of maternal mortality in urban and rural West Africa. METHODS: In this ecological study we used data on maternal mortality and access to obstetric services from two population-based studies conducted in 16 sites in eight West African countries: the Maternal Mortality and Obstetric Care in West Africa (MAMOCWA) study in rural Sénégal, Guinea-Bissau and The Gambia and the Morbidité Maternelle en Afrique de l'Ouest (MOMA) study in urban Burkina Faso, Côte d'Ivoire, Mali, Mauritanie, Niger and Sénégal. RESULTS: In rural areas, maternal mortality, excluding early pregnancy deaths, was 601 per 100,000 live births, compared with 241 per 100,000 for urban areas [RR = 2.49 (CI 1.77-3.59)]. In urban areas, the vast majority of births took place in a health facility (83%) or with a skilled provider (69%), while 80% of the rural women gave birth at home without any skilled care. There was a relatively close link between levels of maternal mortality and the percentage of births with a skilled attendant (r = -0.65), in hospital (r = -0.54) or with a Caesarean section (r = -0.59), with marked clustering in urban and rural areas. Within urban or rural areas, none of the process indicators were associated with maternal mortality. CONCLUSION: Despite the limitations of this ecological study, there can be little doubt that the huge rural-urban differences in maternal mortality are due, at least in part, to differential access to high quality maternity care. Whether any of the indicators examined here will by themselves be good enough as a proxy for maternal mortality is doubtful however, as more than half of the variation in mortality remained unexplained by any one of them.

Seasonal variation in direct obstetric mortality in rural Senegal: role of malaria?

We explore a possible link between malaria and maternal death in a rural area of Senegal by assessing the seasonal pattern of maternal mortality by cause and examining whether this pattern coincides with the malaria season. Overall mortality in women 15-49 years of age did not differ by season, while maternal and direct obstetric deaths were significantly more frequent during the rainy/malaria season than during the rest of the year, even after adjusting for place of delivery.

[Verbal autopsy to measure maternal mortality in rural Senegal]. / Application de l'autopsie verbale dans la mesure de la mortalité maternelle en milieu rural au Sénégal.

OBJECTIVES: The aim of this paper is to study the use of verbal autopsy in order to assess maternal mortality indicators in rural settings and to determine the limits and difficulties related to that practice. MATERIAL AND METHODS: This study was carried out in 3 rural sites (Niakhar in the region of Fatick, Bandafassi in Tambacounda region and Mlomp in the region of Ziguinchor). These sites had been under demographic and epidemiological surveillance for several years. Data were collected through two sources: a questionnaire filled out by data collectors during the demographic surveillance and a complementary survey done by an epidemiologist among families completed by information from the registers of health structures. For all female deaths (15-49 years), the detailed sequence of the events leading to the death were stated in a clinical file of verbal autopsy. All the files had been submitted to two independent obstetricians for analysis. The character of maternal death and the cause of the death (direct, indirect ou undetermined) were processed. The discordant cases were submitted to another expert epidemiologist for analysis. The 10th international classification of diseases of WHO was used as a reference to identify maternal deaths and their causes. RESULTS: This demographic surveillance has led to a complete registration of female deaths and the analysis of female deaths has helped to measure maternal indicators during the observed time period. Among the 471 female deaths, 97 maternal deaths were identified in Niakhar, 36 in Bandafassi and 10 in Mlomp. The proportion of maternal deaths was 30.6% in Niakhar, 32.7% in Bandafassi and 22.7% in Mlomp. The ratio of maternal mortality was 575 per 100,000 live births (LB) in Niakhar, 930/100,000 live births in Bandafassi and 436/100,000 LB in Mliomp. The risk of maternal death was 1 women in 21 in Niakhar, 1 in 16 in Bandafassi and 1 in 41 in Mlomp. Maternal mortality rate was 13.3/10,000 reproductive age women in Niakhar, 17/10,000 in Bandafassi and 6.9/10,000 in Mlomp. Sociocultural limits related to interdiction in the society, and language barriers are seen as limits for applying verbal autopsy practices. Also, a lack of precision in data collection because of lack of information delivered by the interviewee or because of lack of experience of the interviewer could be limitations. This study carried out in a rural setting could not show national maternal mortality level. It takes time to complete verbal autopsy leading to excessive cost. CONCLUSION: Verbal autopsy remains an interesting method for measuring maternal mortality. It has advantages in rural areas where many deliveries still occur at home. Further accuracy in data collection is needed for a precise analysis of each case.

[Water contacts in dracunculiasis-infected patients in Mali: transmission risk activities]. / Contacts homme-eau chez des malades atteints de dracunculose au Mali: activités à risque de transmission.

The aim of this study lies in the identification of human activities responsible for the transmission of the Guinea worm in an endemic village in Diema Region in Mali. Human water contacts observations started after a census followed by the implementation of a bi-monthly notification system, carried out from May to November 1993. Water contacts were noticed and observed from the mid-July to the end of November of the same year. The first case of dracunculiasis observed was randomly drawn out of a list of the families with obvious cases. The patent case activities involving either surface water, traditional wells or bore-hole water were recorded for 10 consecutive days. During this observation period, contacts made by other patients with the same water sources were also recorded. After 14 days, the case list was updated and a new case selected out of families previously selected. This cycle was repeated until the end of the study period. A "contact at risk for transmission" was defined by a close correspondence between the location of the worm's emergence and the surface of the skin exposed to water, within two weeks following emergence. Contacts were described according to water sources, activities in relation to water, date, gender and age. Observations were made on 103 patients who had 2506 activities in relation with a water body: 1132 of these activities implied a skin contact with the water. Only 133 (9%) of these water contacts were at risk for transmission, 75% took place during the months of August and September, 80% were related to surface waters and 20% to traditional wells. Woman household activities and boys games were the major activities at risk, in contrast to economic activities (watering cattle). The low proportion of "at risk activities" evaluated in this study suggests that a small number of water contacts is sufficient to maintain the transmission. The case implications of the current eradication strategy might not be sufficient alone to break the transmission and should therefore be associated with a reinforcement of the use of filters for drinking water together with an health education.

[Climate variability and number of deaths attributable to malaria in the Niakhar area, Senegal, from 1984 to 1996]. / Variations climatiques et mortalité attribuée au paludisme dans la zone de Niakhar, Sénégal, de 1984 à 1996.

There are a number of reasons why climate, in certain physical and social environments, could have an impact on the epidemiology of malaria. Events, such as floods or drought, are related to the number of malaria cases and deaths, both seasonally and interannually. At a smaller scale, this study analyses the relation between climate variability and the variability in the number of deaths attributable to malaria in Niakhar, Senegal. The Niakhar area has a population of 30,000 and has been under demographic surveillance system since 1984. The rainfall in this region is highly seasonal, with a rainfall maximum in August and almost no rain between October/November and May/June. In addition to this seasonal cycle, rainfall also varies greatly from year to year (interannual variation). Over the 13 years, there were 661 deaths attributed to malaria with a marked interannual variability (range from 23 to 100, with a median of 43). There was also a strong seasonality in mortality, with nearly all deaths (89.1%) occurring between August and December. The number of deaths peaks in October, two months after the rainfall peak. Standardised monthly values were calculated for each climatic series (rainfall, relative humidity, temperature) as well as standardised five-month and monthly values of the number of deaths attributed to malaria between August and December. Correlation coefficients were calculated between these standardised values. The correlation between the variability in August rainfall and the variability in the number of deaths attributed to malaria between August and December was positive and statistically significant (r = +0.61, p = 0.02). In addition, highly significant cross-correlations were found between monthly rainfall series and monthly mortality series at one- and two-month lag (r = + 0.43, p = 0.0004 for one-month lag; r = + 0.26, p = 0.03 for two-month lag). This correlation is somewhat lower than the correlation of August rainfall alone with August to December mortality, but the result adds confidence to the signal given the increased degrees of freedom in the analysis. Similar, but slightly weaker, results were found when precipitation data were replaced with surface humidity data. Results with temperature were less clear; while temperature could in some circumstances have a direct impact on malaria, in this case here it is possible that the weak negative correlation between malaria deaths and temperature arises mainly because precipitation is physically connected to both the indices, correlating positively with malaria and negatively with temperature. The availability of a continuous demographic and medical survey since 1984 in a region of highly variable rainfall has created a rare opportunity to analyse with some confidence a climate versus malaria relationship. The findings are consistent with our understanding of the proposed link between rainfall and conditions for the reproduction of the malaria vector, leading to a lag time (here of one to two months) between anomalies of rainfall and deaths attributable to malaria. These results may have practical implications in Sub-Saharan regions marked by a great seasonal and interannual variability in rainfall by providing a simple tool to forecast the impact of climate variability on malaria mortality.

[Investigation of a shigellosis outbreak in a rural zone of Senegal]. / Investigation d'une épidémie de shigellose en zone rurale au Sénégal.

The investigation of this outbreak took place in Niakhar (IRD project study area), a rural area located 150 km East of Dakar. Covering 30 villages, with a population of about 30,000 inhabitants, the area has been under demographic and epidemiological surveillance. In 1999, the surveillance allowed 973 cases of shigellosis to be recorded out of 1,751 cases of dysenteric diarrhoeas. The outbreak reached a peak during the raining season (73% of the cases in September and October). All the villages and all age groups were concerned. The attack rate in the population was 3%. During the same period, 22 deaths were attributed to shigellosis, leading to a lethality of 2.3%. Children under five were the most affected. The bacteriological examination isolated S. flexneri in 72% of 12 stools samples and S. dysenteriae A1 (SD1) in 14%. All serotypes were resistant to ampicillin and susceptible to quinolones. Susceptibility to cotrimoxazole was unconstant. Apart from the usual factors involved in the spread of diarrhoeas, the main reason evoked to explain the duration of the epidemic has been the lack of adequate emergency antibiotherapy treatment. Quinolones, recommended by the health authorities, could not be provided by health services. The identification of the SD1 serotype confirmed its involvement in the outbreak of shigellosis. The exact role of S. flexneri in shigellosis epidemics should be further studied.

Decline of infant and child mortality rates in rural Senegal over a 37-year period (1963-1999).

BACKGROUND: In spite of an improving trend, childhood mortality in rural sub-Saharan Africa remains high and has recently risen in some countries. The factors associated with the long-term decline in childhood mortality are poorly known, due to a lack of data. METHODS: A Senegalese rural population has been under demographic surveillance since 1963. Infant and under-5 mortality rates were calculated for different periods to generate a long-term trend in childhood mortality. Evolution of age and seasonal patterns of mortality were observed. FINDINGS: During the observation period (1963-1999), infant and under-5 mortality rates decreased from 223 per thousand to 80 per thousand and 485 per thousand to 213 per thousand , respectively, with a constant annual rate of decline in the probability of dying since the 1960s (-3.7% and -3.1%, respectively). The age pattern of the under-5 mortality changed drastically, with a large decrease in the death rate between 6 and 24 months of age (from 321 per thousand to 87 per thousand ). This change took place during the 1970s. The seasonal variation, characterized by a greater proportion of deaths during the rainy season, was very marked during the 1960s, then decreased during the 1980s but it has tended to increase again in the 1990s, particularly among children 1-4 years old. CONCLUSION: This study confirms the long-term trend of decrease in child mortality in rural West Africa. Historical knowledge on healthcare developments suggests that immunizations have contributed to the decrease and the change in the age pattern. The re-emergence of malaria seems the most likely explanation for the recent rebound in seasonal variation. Attention to immunization and malaria should continue to be a priority.

Comparison of a digestion-sedimentation technique with the Kato-Katz technique in the detection and quantification of S. mansoni eggs in light to moderate infections.

A comparison between a digestion-sedimentation technique (DST) and the Kato-Katz thick smear technique (KKT) in the detection and quantification of Schistosoma eggs in stool was carried out in 551 subjects. Specimen were collected one or two years after treatment with praziquantel from subjects living in a schistosomiasis endemic area of Mali. One hundred infections missed by the KKT were detected by the DST. Conversely, 35 infections missed by the DST were detected by the KKT (88% were light infections). More subjects were classified as lightly infected by the DST (p < 10(-3)) and more subjects were classified as moderately infected (101-400 epg) by the KKT (p = 0.02). The KKT produced higher counts than the DST among the youngest age group which was also the most infected. The principal advantage of the DST over the KKT was its better sensitivity to detect light infections resulting from a larger amount of stool processed.