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Between May 2017 and November 2018, Greece has experienced a severe measles outbreak with a total of 3258 cases reported, after reaching its goal of eliminating measles since 2014–2015. In this study, we aimed to investigate the origin and the dispersal patterns of the measles strains that circulated in Greece during this outbreak and to identify possible transmission patterns of measles virus (MeV) in the country. Of the 832 measles suspect cases referred to the National Measles and Rubella Reference Laboratory for MeV RNA detection, 131 randomly selected positive samples, representative of the temporal and spatial distribution of the laboratory-confirmed measles cases in Greece, were processed for genotypic identification by an RT-PCR amplification of a 598 bp fragment containing the 450 bp hypervariable region of the measles virus N gene. Phylogenetic analysis was carried out by the approximate maximum likelihood method (ML) under the generalized time-reversible (GTR + cat) model. All samples analyzed were found to belong to genotype B3. Comparative analysis with other European and reference measles strains revealed three separate major clusters and other multiple viruses circulating simultaneously in Greece. They were all isolated from three main community groups, Greek-Roma children, non-minority Greek nationals and immigrants/refugees, a finding that is in accordance with what was also observed in the last two measles outbreaks in 2005–2006 and 2010–2011. Notably, for one of the three clusters, no similarity was detected with previously reported prototype strains. Our results indicate the need for a more intensive vaccination program against measles amongst minority populations and in refugee hot-spots as well as the importance of molecular surveillance as a tool for monitoring measles outbreaks.

A critical component of laboratory surveillance for measles is the genetic characterization of circulating wildtype viruses. The World Health Organization (WHO) Measles and Rubella Laboratory Network (LabNet), provides for standardized testing in 183 countries and supports genetic characterization of currently circulating strains of measles viruses. The goal of this report is to describe the lessons learned from nearly 20 years of virologic surveillance for measles, to describe the global databases for measles sequences, and to provide regional updates about measles genotypes detected by recent surveillance activities. Virologic surveillance for measles is now well established in all of the WHO regions, and most countries have conducted at least some baseline surveillance. The WHO Global Genotype Database contains >7000 genotype reports, and the Measles Nucleotide Surveillance (MeaNS) contains >4000 entries. This sequence information has proven to be extremely useful for tracking global transmission patterns and for documenting the interruption of transmission in some countries. The future challenges will be to develop quality control programs for molecular methods and to continue to expand virologic surveillance activities in all regions.

Romania is currently facing a prolonged measles outbreak. The aim of the study was to analyse the circulating human measles virus (HMV) strains by combining whole genome sequencing (WGS) with phylogenetic analysis, with a focus on the haemagglutinin gene. We conducted an observational study in the first five months of 2024, in which 168 patients diagnosed with measles were randomly included. We have evaluated the clinical and epidemiological differences between children and adults. Screening for samples to be sequenced was performed with a commercial kit (PrimerDesign). WGS was done on Illumina MiSeq platform and phylogenetic analysis was performed with ML FastTree. No significant epidemiological and clinical differences between patients in the two age groups were identified. WGS was successfully performed for a number of 124 HMV strains. Genotype analysis indicated all the sequences as D8, except one that was B3. Phylogenetic analysis identified two well supported clusters, suggestive for at least two local transmission networks in Romania. One large transmission network (n = 108) consisted of sequences both from adults and children. Only one sequence from outside Romania (reported in Russia in 2023) clustered within this group. Another small transmission cluster was identified (14 sequences of which 11 from patients infected in the spring of 2024 and three in 2022). A few differences between the two co-circulating viral variants/clusters were observed. The median duration of hospitalisation was 2 days longer for patients in smaller cluster compared to those in the larger one (p = 0.019). Furthermore, these two clusters presented different mutation profiles in the hemagglutinin (HA) and neuraminidase (N) genes with implications for molecular surveillance. The current measles epidemic in Romania is driven mainly by two D8 genotype variants with different mutation profiles and slightly different severity of the disease, highlighting the usefulness of sustained molecular surveillance.

We used whole-genome sequencing to investigate a dual-genotype outbreak of measles occurring after the XXI Olympic Winter Games in Vancouver, Canada. By sequencing 27 complete genomes from H1 and D8 genotype measles viruses isolated from outbreak cases, we estimated the virus mutation rate, determined that person-to-person transmission is typically associated with 0 mutations between isolates, and established that a single introduction of Hi virus led to the expansion of the outbreak beyond Vancouver. This is the largest measles genomics project to date, revealing novel aspects of measles virus genetics and providing new insights into transmission of this reemerging viral pathogen.

The complete genomic sequences of 9 measles vaccine strains were compared with the sequence of the Edmonston wild-type virus. AIK-C, Moraten, Rubeovax, Schwarz, and Zagreb are vaccine strains of the Edmonston lineage, whereas CAM-70, Changchun-47, Leningrad-4 and Shanghai-191 were derived from 4 different wild-type isolates. Nucleotide substitutions were found in the noncoding regions of the genomes as well as in all coding regions, leading to deduced amino acid substitutions in all 8 viral proteins. Although the precise mechanisms involved in the attenuation of individual measles vaccines remain to be elucidated, in vitro assays of viral protein functions and recombinant viruses with defined genetic modifications have been used to characterize the differences between vaccine and wild-type strains. Although almost every protein contributes to an attenuated phenotype, substitutions affecting host cell tropism, virus assembly, and the ability to inhibit cellular antiviral defense mechanisms play an especially important role in attenuation.

Globally, 24 measles virus genotypes have been detected, and these genotypes have been classified into eight clades based on 450 nucleotides of the C-terminal region of the nucleoprotein gene. Genotype B3 is predominant in Africa, but there are limited data from Tanzania since the introduction of the second dose of measles-containing vaccine in 2014. A total of 129 nasopharyngeal samples and corresponding sera were collected during measles outbreaks between 2022 and 2024. Viral RNA was extracted from nasopharyngeal swabs prior to RT-qPCR and sequencing of a 450-nucleotide segment of the nucleoprotein (N) gene. Out of 129 nasopharyngeal samples, 73 (56%) were successfully amplified and identified as endemic measles virus genotype B3. Nine distinct sequence identifiers were detected, with seven reported for the first time in the MeaNS database. All the Tanzanian B3 sequences were closely related and clustered with genotype B3, similar to those reported from Kenya, Ethiopia, Rwanda, Uganda, Burundi, and South Africa. On multivariate analysis, only inpatient admission status (p = 0.014) and positive measles IgM (p = 0.003) were found to be associated with positive measles RT-qPCR. Our results indicate that genotype B3 remains endemic in Tanzania and is closely related to other genotype B3 reported globally, indicating its high stability and transmissibility.

Waning immunity or secondary vaccine failure (SVF) has been anticipated by some as a challenge to global measles elimination efforts. Although such cases are infrequent, measles virus (MeV) infection can occur in vaccinated individuals following intense and/or prolonged exposure to an infected individual and may present as a modified illness that is unrecognizable as measles outside of the context of a measles outbreak. The immunoglobulin M response in previously vaccinated individuals may be nominal or fleeting, and viral replication may be limited. As global elimination proceeds, additional methods for confirming modified measles cases may be needed to understand whether SVF cases contribute to continued measles virus (MeV) transmission. In this report, we describe clinical symptoms and laboratory results for unvaccinated individuals with acute measles and individuals with SVF identified during MeV outbreaks. SVF cases were characterized by the serological parameters of high-avidity antibodies and distinctively high levels of neutralizing antibody. These parameters may represent useful biomarkers for classification of SVF cases that previously could not be confirmed as such using routine laboratory diagnostic techniques.

Purpose In 2023–2024, measles cases progressively increased in Europe. Multiple outbreaks were reported and viral strains with three-nucleotide mutations potentially compromising diagnostic testing were identified. We analyzed the first cases of measles reported in Lazio (Central Italy) from September 2023 to March 2024, combining molecular characterization and phylogenetic analysis with epidemiological investigation to identify transmission chains and evaluate the sensitivity of PCR tests adopted on circulating viral strains. Methods We tested samples collected through routine measles and rubella surveillance for IgM, IgG and Real-Time PCR. We sequenced positive samples with higher viral titers using an amplicon-based whole-genome next-generation sequencing (WG-NGS) approach and performed mutational and phylogenetic analysis. Furthermore, we tested the sensitivity of the PCR molecular diagnostic assay adopted in our laboratory to identify the mutated strains. Results Of the 39 suspected cases, 28 were confirmed. Endemic cases were 82%; of these, 78% were sporadic at epidemiological investigation. From 21 high-titer samples, we obtained 14 strains belonging to the D8 genotype. Phylogenetic analysis identified four distinct clusters: three associating 50% of sporadic cases, and one confirming the epidemiological investigation. Several mutational patterns were identified, one of which had three nucleotide mutations potentially affecting the diagnostic test. However, our routine diagnostic PCR tests are able to detect mutated strains at different dilutions. Conclusion Our results demonstrate that WG-NGS can be used to distinguish transmission chains and identify infection clusters to improve surveillance activity and enable the implementation of more targeted control measures, highlighting the importance of integrated epidemiological and genomic surveillance.

Background Measles, an ongoing public health concern, demands continuous molecular surveillance and virus characterization for elimination. Despite Iran achieving measles elimination status in 2019 through robust molecular testing and vaccination, the COVID-19 pandemic disrupted global vaccination efforts, leading to increased measles-related morbidity and mortality. This study aims to overview measles virus serological and molecular traits in Iran from 1st January 2021 to 30th April 2023. Methods Following World Health Organization and Center for Diseases and Control protocols, serological tests were performed on suspected cases and the nucleoprotein (N) gene of confirmed cases were subsequently amplified using molecular methods and were sequenced afterwards for measles genotyping. Phylogenetic analysis was performed with the obtained sequences. Results Analyzing 17,343 suspected cases from 1st January 2021 to 30th April 2023, 936, 177, and 164 samples were positive using ELISA, quantitative Reverse transcription PCR, and Reverse transcription PCR, respectively. The B3 genotype predominated, notably in Iran’s South East (41%), Central (28%), and South (13%) regions. Provinces bordering countries with measles outbreaks exhibited higher risk of virus importation. Genetic comparisons with measles sequences submitted to NCBI and MeaNS databases revealed direct importation and contact transmission. Conclusion Regular surveillance and genetic analysis are critical for understanding measles transmission and reacting to outbreaks. The COVID-19 pandemic yielded mixed effects on measles cases, enhancing hygiene measures while causing underreporting and vaccination gaps. Vigilance against measles resurgence is crucial, requiring cross-border transmission studies, improving cross-border surveillance and adaptable vaccination strategies.

Of the 24 known measles genotypes, only D8 and B3 are responsible for outbreaks in the last years in Europe, Asia, and America. In this study the H gene of 92 strains circulating between 2015 and 2019 in Lombardy, Northern Italy, and 1273 H sequences available in GenBank were analyzed in order to evaluate the genetic variability and to assess the conservation of the immunodominant sites. Overall, in Lombardy we observed the presence of four different B3 and three different D8 clusters, each one of them including sequences derived from viruses found in both vaccinated and unvaccinated subjects. Worldwide, the residue 400 within the H protein, a position located within the main immune epitope, is mutated in all circulating strains that belong to the two globally endemic genotypes, B3 and D8. Our data demonstrate the usefulness of measles virus (MV) H gene sequencing. Indeed, the monitoring the H protein epitopes of circulating strains could be included in the measles laboratory surveillance activities in order to improve and optimize strategies for measles control, as countries go towards elimination phase.