Epidemiology and genetic characterization of measles strains in Senegal, 2004-2013

Epidemiology of measles in Angola: Results from routine surveillance from 2015 to 2021

Background

Measles, an acute infectious disease of extremely contagious viral aetiology, has been eliminated in some parts of the world. To the best of the authors' knowledge, this is the first study on the epidemiological pattern of the measles virus in Angola, and it was carried out through a review of 7 years of observational retrospective data from the national measles laboratory surveillance programme.

Methods

A retrospective study using national databases on the laboratory surveillance of measles was performed. Patients of all ages with suspected measles from all provinces of Angola were included. Serum samples were used to detect IgM-type measles-virus-specific antibodies by enzyme-linked immunosorbent assay.

Findings

In total, 3690 suspected measles samples were sent to the Instituto Nacional de Investigação em Saúde. There were 962 (26.1%) laboratory-confirmed cases, and the most affected age group was children aged 1-4 years. The highest incidence rate per 100,000 population was found in Benguela (17.9%), followed by Huambo (16.7%) and Cuanza Sul (13.6%). Of the study years, the incidence rate per 1,000,000 population was highest in 2020 (11.9%). The most common complication was diarrhoea (n=406, 42.2%). Of the confirmed cases, 209 (21.7%) were vaccinated, 633 (65.8%) were unvaccinated, and 120 (12.5%) had unknown vaccination status. For all study years, vaccination coverage was <70%.

Interpretation

Measles continues to be a serious problem in Angola, and more efforts are needed to increase measles surveillance and achieve a high percentage of vaccination coverage.

Measles and Rubella Incidence and Molecular Epidemiology in Senegal: Temporal and Regional Trends during Twelve Years of National Surveillance, 2010-2021

We investigated the epidemiology of measles and rubella infections in Senegal based on data from twelve consecutive years of laboratory-based surveillance (2010−2021) and conducted phylogenetic analyses of circulating measles viruses. Sera from measles-suspected cases were collected and tested for measles and rubella-specific IgM antibodies using enzyme-linked immunosorbent assays (ELISA). Throat swabs were collected from patients with clinically diagnosed measles for confirmation by reverse-transcription polymerase chain reaction (RT-PCR) and viral genotyping. Among 8082 laboratory-tested specimens from measles-suspected cases, serological evidence of measles and rubella infection was confirmed in 1303/8082 (16.1%) and 465/6714 (6.9%), respectively. The incidence of rubella is now low—0.8 (95% CI 0.4−1.3) cases per million people in 2021—whereas progress towards measles pre-elimination targets (<1.0 case per million people per year) appears to have stalled; there were 10.8 (95% CI 9.3−12.5) cases per million people in 2021. Phylogenetic analyses revealed that all Senegalese measles strains belonged to genotype B3. The rubella virus sequence obtained in this study was consistent with genotype 1C. Our national surveillance data suggest that despite their low incidence both measles and rubella remain endemic in Senegal with a concerning stagnation in the decline of measles infections that represents a significant challenge to the goal of regional elimination.

Molecular Detection of Human Herpes Viruses in Suspected Measles Serum Samples from Senegal, 2014 to 2017

Herpesviruses are known to cause a diversity of clinical syndromes, ranging from minor cutaneous lesions to life-threatening illnesses, especially in immunocompromised hosts. Here, we investigate retrospectively the contribution of five human herpesviruses, including herpes simplex virus Cytomegalovirus (CMV), the Epstein-Barr virus (EBV), human herpesvirus 6, and varicella zoster virus (VZV) in serum samples collected from measles suspected patients with at least fever and rash. Sera specimens were first tested for serological evidence of measles and rubella virus infection by ELISA, and DNA extracted from an aliquot of each clinical specimen for molecular detection of human herpes viruses by RT-qPCR. A total of 3,358 specimens have been collected and tested for herpes viruses. Nearly half of the overall suspected cases were children younger than 5 years (49.4%). Of the 3,358 sera tested by ELISA, 227 (6.7%) were measles laboratory confirmed and 152 (4.5%) rubella laboratory confirmed. Herpes viruses were detected in 1763 (52.5%), and VZV was the most common with 44.3%, followed by EBV with 10.7%. Coinfections were found in 352 (20%) cases, and the most common co-detections were VZV/EBV or VZV/CMV (169 and 81 cases, respectively). A clear seasonal pattern of VZV, EBV, and CMV identification was observed, with the highest incidence between February and April each year. Results of this investigation provide more insights into cutaneous rash syndrome etiologies in patients sampled in the framework of measles/rubella surveillance in Senegal, which is useful for the guidance of both case definition revision and clinical practice as well as for public health policy.

Reported measles cases, measles-related deaths and measles vaccination coverage in Myanmar from 2014 to 2018

BACKGROUND

There is a global resurgence of measles, consequent upon worldwide stagnating measles vaccination coverage. The study aim was to document trends and characteristics of reported cases of measles, measles-related deaths, and measles vaccination coverage (MCV1-first dose of measles-containing vaccine and MCV2-second dose of measles-containing vaccine) at national and sub-national level in Myanmar over a five year period between 2014 and 2018.

METHODS

This was a descriptive study using routine data collected and submitted to the Expanded Programme on Immunization.

RESULTS

Between 2014 and 2018, there were 2673 measles cases of which 2272 (85%) occurred in 2017 and 2018. Five adjacent regions in lower Myanmar were the most affected: in 2017 and 2018, these regions reported 1647 (73%) of the 2272 measles cases in the country. Overall, 73% of measles cases were laboratory confirmed, 21% were epidemiologically linked, and 6% were clinically compatible (clinical diagnosis only), with more laboratory confirmed cases in recent years. Annual measles-related deaths were either zero or one except in 2016 when there were 21 deaths, all occurring in one remote village. In the recent years, the most commonly affected age groups were 0-8 months, 9 months to 4 years, and ≥ 15 years. Among 1907 measles cases with known vaccination status, only 22% had been vaccinated and 70% of those had only received one dose of vaccine. Annual MCV1 coverage nationally varied from 83 to 93% while annual MCV2 coverage nationally varied from 78 to 87%, with no clear trends over the years. Between 2014 and 2018, a high proportion of the 330 townships had MCV coverage < 95%. Over 80% of measles cases were reported from townships that had MCV coverage < 95%.

CONCLUSION

There have been a large number of measles cases in recent years associated with sub-optimal measles vaccine coverage. Myanmar has already conducted supplemental immunization activities in October and November, 2019. Myanmar also needs to improve routine immunization services and targeted responses to measles outbreaks.

Coverage and Determinants of Full Immunization: Vaccination Coverage among Senegalese Children

Background and Objectives: In line with the global success of immunization, Senegal achieved impressive progress in childhood immunization program. However, immunization coverage is often below the national and international targets and even not equally distributed across the country. The objective of this study is to estimate the full immunization coverage across the geographic regions and identify the potential factors of full immunization coverage among the Senegalese children. Materials and Methods: Nationally representative dataset extracted from the latest Continuous Senegal Demographic and Health Survey 2017 was used for this analysis. Descriptive statistics such as the frequency with percentage and multivariable logistic regression models were constructed and results were presented in terms of adjusted odds ratio (AOR) with a 95% confidence interval (CI). Results: Overall, 70.96% of Senegalese children aged between 12 to 36 months were fully immunized and the coverage was higher in urban areas (76.51%), west ecological zone (80.0%), and among serer ethnic groups (77.24%). Full immunization coverage rate was almost the same between male and female children, and slightly higher among the children who were born at any health care facility (74.01%). Children who lived in the western zone of Senegal were 1.66 times (CI: 1.25–2.21; p = 0.001) and the children of Serer ethnic groups were 1.43 times (CI: 1.09–1.88; p = 0.011) more likely to be fully immunized than the children living in the southern zone and from the Poular ethnic group. In addition, children who were born at health facilities were more likely to be fully immunized than those who were born at home (AOR = 1.47; CI: 1.20–1.80; p < 0.001), and mothers with recommended antenatal care (ANC) (4 and more) visits during pregnancy were more likely to have their children fully immunized than those mother with no ANC visits (AOR: 2.06 CI: 1.19–3.57; p = 0.010). Conclusions: Immunization coverage was found suboptimal by type of vaccines and across ethnic groups and regions of Senegal. Immunization program should be designed targeting low performing areas and emphasize on promoting equal access to education, decision-making, encouraging institutional deliveries, and scaling up the use of antenatal and postnatal care which may significantly improve the rate full immunization coverage in Senegal.

Epidemiologic profile of measles in Central African Republic: A nine year survey, 2007-2015

INTRODUCTION

Measles remains a major public health problem in many developing countries in which vaccination coverage is poor, as is the case in the Central African Republic (CAR). At the beginning of the 2000s, a surveillance system was established in the country, and samples from suspected cases are regularly tested in the laboratory for serological confirmation. Since 2007, when case-by-case monitoring with standardized laboratory databases and monitoring, was set up, no assessment have been performed. Therfore, 9 years later it seemed appropriate to make a first assessment. The aim of the study reported here was to describe the epidemiology of measles in the CAR on the basis of surveillance and laboratory data.

METHOD

A descriptive retrospective study was conducted, based on the databases of the measles surveillance programme and of the Institut Pasteur laboratory in Bangui during the period 2007-2015.

RESULTS

During this study period, the surveillance programme notified 3767 cases. Of these, 2795 (75%) were sent for laboratory confirmation, and 24.6% (687/2795) were confirmed serologically. Of the 1797 cases of measles declared during this period by the surveillance programme, 1110 (61.8%) were confirmed clinically or by epidemiological linkage. The majority of confirmed cases (83.7%; 575/687) occurred in children under 10 years, over half of whom (44.2%; 304/687) were aged 1-4 years. Epidemics occurred regularly between 2011 and 2015, with > 10% of laboratory-confirmed cases. The rate of laboratory investigation was < 80% between 2011 and 2013 but nearly 100% in the other years.

CONCLUSION

Measles remains a common, endemic illness in the CAR. Improved detection will require better measles surveillance, increased vaccination coverage, revision of the investigation forms to include the WHO case definition and training of the health personnel involved in case-finding in the field.

Vaccination coverage and immunization timeliness among children aged 12-23 months in Senegal: a Kaplan-Meier and Cox regression analysis approach

Introduction

Expanded programme on immunizations in resource-limited settings currently measure vaccination coverage defined as the proportion of children aged 12-23 months that have completed their vaccination. However, this indicator does not address the important question of when the scheduled vaccines were administered. We assessed the determinants of timely immunization to help the national EPI program manage vaccine-preventable diseases and impact positively on child survival in Senegal.

Methods

Vaccination data were obtained from the Demographic and Health Survey (DHS) carried out across the 14 regions in the country. Children were aged between 12-23 months. The assessment of vaccination coverage was done with the health card and/or by the mother’s recall of the vaccination act. For each vaccine, an assessment of delay in age-appropriate vaccination was done following WHO recommendations. Additionally, Kaplan-Meier survival function was used to estimate the proportion vaccinated by age and cox-proportional hazards models were used to examine risk factors for delays.

Results

A total of 2444 living children between 12–23 months of age were included in the analysis. The country vaccination was below the WHO recommended coverage level and, there was a gap in timeliness of children immunization. While BCG vaccine uptake was over 95%, coverage decreased with increasing number of Pentavalent vaccine doses (Penta 1: 95.6%, Penta 2: 93.5%: Penta 3: 89.2%). Median delay for BCG was 1.7 weeks. For polio at birth, the median delay was 5 days; all other vaccine doses had median delays of 2-4 weeks. For Penta 1 and Penta 3, 23.5% and 15.7% were given late respectively. A quarter of measles vaccines were not administered or were scheduled after the recommended age. Vaccinations that were not administered within the recommended age ranges were associated with mothers’ poor education level, multiple siblings, low socio-economic status and living in rural areas.

Conclusion

A significant delay in receipt of infant vaccines is found in Senegal while vaccine coverage is suboptimal. The national expanded program on immunization should consider measuring age at immunization or using seroepidemiological data to better monitor its impact.