Shift within age-groups of mumps incidence, hospitalizations and severe complications in a highly vaccinated population. Spain, 1998-2014

Investigating Local Patterns of Mumps Virus Circulation, Using a Combination of Molecular Tools

Mumps is a vaccine-preventable disease caused by the mumps virus (MuV). However, MuV has re-emerged in many countries with high vaccine coverage. The World Health Organization (WHO) recommends molecular surveillance based on sequencing of the small hydrophobic (SH) gene. Additionally, the combined use of SH and non-coding regions (NCR) has been described in different studies, proving to be a useful complement marker to discriminate general patterns of circulation at national and international levels. The aim of this work is to test local-level usefulness of the combination of SH and MF-NCR sequencing in tracing hidden transmission clusters and chains during the last epidemic wave (2015-2020) in Spain. A database with 903 cases from the Autonomous Community of Madrid was generated by the integration of microbiological and epidemiological data. Of these, 453 representative cases were genotyped. Eight different SH variants and thirty-four SH haplotypes were detected. Local MuV circulation showed the same temporal pattern previously described at a national level. Only two of the thirteen previously identified outbreaks were caused by more than one variant/haplotype. Geographical representation of SH variants allowed the identification of several previously undetected clusters, which were analysed phylogenetically by the combination of SH and MF-NCR, in a total of 90 cases. MF-NCR was not able to improve the discrimination of geographical clusters based on SH sequencing, showing limited resolution for outbreak investigations.

Comparison of circulation patterns of mumps virus in the Netherlands and Spain (2015-2020)

Background

Mumps is a viral infection mainly characterized by inflammation of the parotid glands. Despite of vaccination programs, infections among fully vaccinated populations were reported. The World Health Organization (WHO) recommends molecular surveillance of mumps based on sequencing of the small hydrophobic (SH) gene. The use of hypervariable non-coding regions (NCR) as additional molecular markers was proposed in multiple studies. Circulation of mumps virus (MuV) genotypes and variants in different European countries were described in the literature. From 2010 to 2020, mumps outbreaks caused by genotype G were described. However, this issue has not been analyzed from a wider geographical perspective. In the present study, sequence data from MuV detected in Spain and in The Netherlands during a period of 5  years (2015- March 2020) were analyzed to gain insights in the spatiotemporal spread of MuV at a larger geographical scale than in previous local studies.

Methods

A total of 1,121 SH and 262 NCR between the Matrix and Fusion protein genes (MF-NCR) sequences from both countries were included in this study. Analysis of SH revealed 106 different haplotypes (set of identical sequences).

Results

Of them, seven showing extensive circulation were considered variants. All seven were detected in both countries in coincident temporal periods. A single MF-NCR haplotype was detected in 156 sequences (59.3% of total), and was shared by five of the seven SH variants, as well as three minor MF-NCR haplotypes. All SH variants and MF-NCR haplotypes shared by both countries were detected first in Spain.

Discussion

Our results suggest a transmission way from south to north Europe. The higher incidence rate of mumps in Spain in spite of similar immunization coverage in both countries, could be associated with higher risk of MuV exportation. In conclusion, the present study provided novel insights into the circulation of MuV variants and haplotypes beyond the borders of single countries. In fact, the use of MF-NCR molecular tool allowed to reveal MuV transmission flows between The Netherlands and Spain. Similar studies including other (European) countries are needed to provide a broader view of the data presented in this study.

Mumps resurgence in a highly vaccinated population: Insights gained from surveillance in Canada, 2002-2020

Although mumps vaccination has been routine in Canada for decades, mumps cases and outbreaks continue to occur periodically. Mumps surveillance, including monitoring of the mumps virus genotype associated with disease activity, is important to document baseline activity and to advance further research into vaccine effectiveness. Here we describe a detailed analysis of mumps cases that have been detected in Canada from 2002 to 2020, with a focus on the mumps molecular epidemiology. In total, 7395 cases of mumps were reported to the surveillance system, with outbreaks occurring in the years 2007, 2010 and 2016 to 2018. Adolescents and young adults aged 15 to 29 years had the highest risk of being a case (rate ratios ranging from 1.50 to 2.29), compared to adults aged 30 to 39. Genotypes of mumps viruses were determined in 3225 specimens. Genotype G was predominantly detected (96% of genotyped specimens) and was first reported in 2005. Other genotypes were more likely to be detected in cases that also reported travel (or were linked to imported cases) than the cases with genotype G detected (p < 0.0001). The genotype G viruses had little sequence diversity in the 316 nucleotide window used for genotyping (the small hydrophobic protein gene) and mainly belonged to a single phylogenetic lineage that included the MuVi/Sheffield.GBR/1.05 reference sequence. The analysis of over ten years of data has demonstrated that mumps genotype G, specifically belonging to a single lineage, the Sheffield lineage, is the endemically circulating virus in Canada. This lineage is seen also in other countries using the genotype A vaccine. Mumps remains endemic despite high MMR vaccination coverage which has been sufficient to eliminate circulation of measles and rubella in Canada, raising the hypothesis of the evolution towards a vaccine escape mumps virus.

Increase of Diversity of Mumps Virus Genotype G SH Variants Circulating Among a Highly Immunized Population: Spain, 2007-2019

MuV caused three epidemic waves in Spain since genotype G emerged in 2005, despite high vaccination coverage. SH gene sequencing according to WHO protocols allowed the identification of seven relevant variants and 88 haplotypes. While the originally imported MuVi/Sheffield.GBR/1.05/-variant prevailed during the first two waves, it was subsequently replaced by other variants originated by either local evolution or importation, according to the additional analysis of hypervariable NCRs. The time of emergence of the MRCA of each MuV variant clade was concordant with the data of the earliest sequence. The analysis of Shannon entropy showed an accumulation of variability on six particular positions as the cause of the increase on the number of circulating SH variants. Consequently, SH gene sequencing needs to be complemented with other more variable markers for mumps surveillance immediately after the emergence of a new genotype, but the subsequent emergence of new SH variants turns it unnecessary.

Influence of Ribavirin on Mumps Virus Population Diversity

Frequent mumps outbreaks in vaccinated populations and the occurrence of neurological complications (e.g., aseptic meningitis or encephalitis) in patients with mumps indicate the need for the development of more efficient vaccines as well as specific antiviral therapies. RNA viruses are genetically highly heterogeneous populations that exist on the edge of an error threshold, such that additional increases in mutational burden can lead to extinction of the virus population. Deliberate modulation of their natural mutation rate is being exploited as an antiviral strategy and a possibility for rational vaccine design. The aim of this study was to examine the ability of ribavirin, a broad-spectrum antiviral agent, to introduce mutations in the mumps virus (MuV) genome and to investigate if resistance develops during long-term in vitro exposure to ribavirin. An increase in MuV population heterogeneity in the presence of ribavirin has been observed after one passage in cell culture, as well as a bias toward C-to-U and G-to-A transitions, which have previously been defined as ribavirin-related. At higher ribavirin concentration, MuV loses its infectivity during serial passaging and does not recover. At low ribavirin concentration, serial passaging leads to a more significant increase in population diversity and a stronger bias towards ribavirin-related transitions, independently of viral strain or cell culture. In these conditions, the virus retains its initial growth capacity, without development of resistance at a whole-virus population level.

Mumps virus outbreak related to a water pipe (narghile) shared smoking

INTRODUCTION

This study describes a mumps outbreak among a group of young people who shared a same narghile to smoking. Saliva and blood samples were obtained from 3 cases for RT-PCR and serology respectively.

METHODS

The notification of a mumps case started an epidemiological investigation. Information of other 6 additional symptomatic persons who had gathered with the case in a discotheque where they smoking in a same narghile was achieved. RT-PCR positive samples were genotyped by sequencing.

RESULTS

The 7 patients resided in 3 different municipalities, and they do not have get together for more than a month until the meeting in the discotheque. Four cases were confirmed by RT-PCR and/or IgM determinations. The genomic investigation showed identical nucleic sequences.

CONCLUSIONS

This outbreak is consequence of the common use of a narghile to smoking. The public usage of these water pipes should be regulated.

Mumps virus outbreak related to a water pipe (narghile) shared smoking

INTRODUCTION

This study describes a mumps outbreak among a group of young people who shared a same narghile to smoking. Saliva and blood samples were obtained from 3cases for RT-PCR and serology respectively.

METHODS

The notification of a mumps case started an epidemiological investigation. Information of other 6additional symptomatic persons who had gathered with the case in a discotheque where they smoking in a same narghile was achieved. RT-PCR positive samples were genotyped by sequencing.

RESULTS

The 7patients resided in 3different municipalities, and they do not have get together for more than a month until the meeting in the discotheque. Four cases were confirmed by RT-PCR and/or IgM determinations. The genomic investigation showed identical nucleic sequences.

CONCLUSIONS

This outbreak is consequence of the common use of a narghile to smoking. The public usage of these water pipes should be regulated.

Cases of aseptic meningitis after vaccination against mumps in Russia (2009-2019)

OBJECTIVES

Mumps is a highly contagious viral infection prevented by immunization with live attenuated vaccines. Mumps vaccines have proven to be safe and effective; however, rare cases of aseptic meningitis (AM) can occur after vaccination. The range of meningitis occurrence varies by different factors (strain, vaccine producer, and so on). Monovaccines or divaccines (mumps-measles vaccine), prepared from the strain Leningrad-3 (L-3), are used in Russia. Meningitis occurrence after vaccination has been established previously as very low. Nevertheless, with the number of children being vaccinated every year, vaccine-associated AM cases still occur. There is no official statistics on AM incidence after mumps vaccines, and information on AM features as an adverse event of mumps vaccination is limited and mostly devoted to vaccines, prepared from strains other than L-3.

STUDY DESIGN

The study included patients with AM who were vaccinated against mumps in the previous 30 days before the present disease onset during 2009-2019.

METHODS

Patients admitted to Infectious Clinical Hospital No. 1, Moscow, Russia, with AM were observed by a pediatrician and were screened for etiological agents of meningitis.

RESULTS

Seven patients were enrolled, and clinical features and the course of infection are presented.

CONCLUSIONS

Detection of only 7 cases of AM associated with mumps vaccination during the 10-year period supports very low occurrence of this adverse event after immunization with the L-3 strain-based mumps vaccines. Nevertheless, the annual number of AM cases that occur after mumps vaccination remains unknown and poorly diagnosed in practice because of the low awareness of physicians of this adverse reaction. Detection and objective coverage of such cases can lead to a weakening of 'antivaccination' moods in a society and to restoration of confidence in the healthcare system.

Epidemiology of laboratory-confirmed mumps infections in South Africa, 2012-2017: a cross-sectional study

Background

Data on the burden of mumps in South Africa are limited and the epidemiology of mumps in this setting is not well understood. We present an analysis of mumps data in South Africa from 2012 to 2017.

Methods

This cross-sectional study included secondary data on laboratory-confirmed mumps infections from 2012 to 2017, archived at the South African National Health Laboratory Services’ data repository as well as from four private laboratories. Mumps-specific immunoglobulin M (IgM) and/or viral nucleic acid positive results represented acute infections. We used age-specific mid-year population estimates for each study year as denominators when calculating annual cumulative incidence. Seasonality was based on the season that showed a peak in infections.

Results

Out of 48,580 records obtained from the public and private sectors, 46,713 (96.2%) were from the private sector. Over the study period, there were 7494 acute infections, 7085 (94.5%) of which were recorded in the private sector. Of these 7494 infections, 3924 (52.4%) occurred in males. The proportion of samples tested that were IgM positive was 18.6% (1058/5682) in 2012, 15% (1016/6790) in 2013, 15.8% (1280/8093) in 2014, 15.5% (1384/8944) in 2015, 13.1% (1260/9629) in 2016 and 15.8% (1496/9442) in 2017. The cumulative incidence rate per 100,000 was highest in children between one and 9 years throughout the study period. The cumulative incidence of infections was highest in the Western Cape, Gauteng and the Northern Cape. Infections peaked in June and November.

Conclusion

Laboratory-confirmed mumps infections predominantly occurred in spring, affecting children below 10 years of age and individuals who were male. There were fewer tests performed in the public sector compared to the private sector. Since only laboratory data was analysed our results represent and underestimate of disease burden. Further studies that include clinical data are required to provide better estimates of disease burden in South Africa.

Mumps outbreaks: A problem in need of solutions

OBJECTIVES

To discuss what is presently known about recent mumps outbreaks and what solutions can be suggested to ensure more complete protection against mumps.

METHODS

PubMed was used to search for all of the studies published over the last 15 years using the key words "mumps" or "mumps virus" or "mumps vaccine". More than 1500 articles were found, but only those published in English or providing evidence-based data were included in the evaluation.

RESULTS

Prevention of mumps remains an unsolved problem. Available vaccines are effective but the protection they evoke declines over time. The use of booster doses can control outbreaks but it is not precisely defined whether they can prevent them. The rapid decline of antibody levels could limit the impact of the introduction of a third dose in the recommended immunization schedule. Furthermore, in most of the areas, mumps viral strains that are genetically different from those included in the vaccines are emerging and this might favour vaccine escape. However, also for this problem, its real relevance in favouring outbreak development is not precisely defined.

CONCLUSIONS

The true reasons for the development of mumps outbreaks in people with very high vaccination coverage are not clearly understood. The use of a booster dose or the preparation of vaccines containing the emerging serotypes are possible solutions, but both have some limitations. Further studies mainly devoted to improve our knowledge of the immune response to mumps vaccines are needed before long-term effective mumps vaccines can be prepared and outbreaks can be avoided.

Mumps disease in Beijing in the era of two-dose vaccination policy, 2005-2016

BACKGROUND

Since the introduction of mumps-containing vaccines (MuCV) in 1995 in Beijing, two-dose MuCV vaccination policy has been used, with the 1st and 2nd doses given at 18 months and 6 years of age, respectively.

METHODS

Mumps epidemiology during 2005-2016 was described using surveillance data. Vaccine effectiveness (VE) of MuCV against disease was estimated for cases born during 2002-2009 and reported in 2016. VE against complications was estimated for all cases. MuCV coverage was estimated for children born during 1999-2015 using data from Beijing Immunization Information System.

RESULTS

Overall mumps incidence decreased from 30.38/100,000 persons in 2005 to 10.26/100,000 persons in 2016. Incidence declines in children aged <15 years. No significant incidence change occurred in adults aged ≥20 years. Incidence in persons aged 15-19 years increased by 132.73% in 2012 when compared with in 2005. Rates of meningitis/encephalitis, orchitis, and other complications among cases decreased during 2005-2016. The majority (97%) of outbreaks occurred in schools. Total number of outbreaks and average outbreak size decreased during 2005-2016. Among outbreak-related cases, 69.54%, 29.67% and 0.79% had received 0 dose, 1dose and 2 doses of MuCV, respectively. Coverage of the 1st MuCV dose at 2-5 years of age increased by 42.75% during 2005-2016. Coverage of the 2nd MuCV dose at 6-14 years of age increased by 12.87% during 2013-2016. Overall VE estimates of MuCV against mumps disease were 74.51% (95% CI: 65.57-81.34%) for 1 dose and 83.16% (95% CI: 78.60-86.31%) for 2 doses. Both VE estimates increased by birth cohorts. VE estimate against complications for 2-dose MuCV was higher than for 1 dose.

CONCLUSIONS

Increasing MuCV coverage achieved declining mumps incidence and complication rate. Current epidemiology supported 2-dose MuCV vaccination policy. The incidence rise in persons aged 15-19 years in 2012 and waning immunity for the 2nd MuCV dose merited close follow-up.