Mumps outbreak in vaccinated children in Gipuzkoa (Basque Country), Spain

Meta-analysis of the effects of ambient temperature and relative humidity on the risk of mumps

Many studies have shown that the relationship between ambient temperature, relative humidity and mumps has been highlighted. However, these studies showed inconsistent results. Therefore, the goal of our study is to conduct a meta-analysis to clarify this relationship and to quantify the size of these effects as well as the potential factors. Systematic literature researches on PubMed, Embase.com, Web of Science Core Collection, Cochrane library, Chinese BioMedical Literature Database (CBM) and China National Knowledge Infrastructure (CNKI) were performed up to February 7, 2022 for articles analyzing the relationships between ambient temperature, relative humidity and incidence of mumps. Eligibility assessment and data extraction were conducted independently by two researchers, and meta-analysis was performed to synthesize these data. We also assessed sources of heterogeneity by study region, regional climate, study population. Finally, a total of 14 studies were screened out from 1154 records and identified to estimate the relationship between ambient temperature, relative humidity and incidence of mumps. It was found that per 1 °C increase and decrease in the ambient temperature were significantly associated with increased incidence of mumps with RR of 1.0191 (95% CI: 1.0129–1.0252, I² = 92.0%, Egger’s test P = 0.001, N = 13) for per 1 °C increase and 1.0244 (95% CI: 1.0130–1.0359, I² = 86.6%, Egger’s test P = 0.077, N = 9) for per 1 °C decrease. As to relative humidity, only high effect of relative humidity was slightly significant (for per 1 unit increase with RR of 1.0088 (95% CI: 1.0027–1.0150), I² = 72.6%, Egger’s test P = 0.159, N = 9). Subgroup analysis showed that regional climate with temperate areas may have a higher risk of incidence of mumps than areas with subtropical climate in cold effect of ambient temperature and low effect of relative humidity. In addition, meta-regression analysis showed that regional climate may affect the association between incidence of mumps and cold effect of ambient temperature. Our results suggest ambient temperature could affect the incidence of mumps significantly, of which both hot and cold effect of ambient temperature may increase the incidence of mumps. Further studies are still needed to clarify the relationship between the incidence of mumps and ambient temperature outside of east Asia, and many other meteorological factors. These results of ambient temperature are important for establishing preventive measures on mumps, especially in temperate areas. The policy-makers should pay more attention to ambient temperature changes and take protective measures in advance.

Mumps: an Update on Outbreaks, Vaccine Efficacy, and Genomic Diversity

Mumps is an acute viral infection characterized by inflammation of the parotid and other salivary glands. Persons with mumps are infectious from 2 days before through 5 days after parotitis onset, and transmission is through respiratory droplets. Despite the success of mumps vaccination programs in the United States and parts of Europe, a recent increase in outbreaks of mumps virus infections among fully vaccinated populations has been reported. Although the effectiveness of the mumps virus component of the measles-mumps-rubella (MMR) vaccine is suboptimal, a range of contributing factors has led to these outbreaks occurring in high-vaccination-coverage settings, including the intensity of exposure, the possibility of vaccine strain mismatch, delayed implementation of control measures due to the timeliness of reporting, a lack of use of appropriate laboratory tests (such as reverse transcription-PCR), and time since last vaccination. The resurgence of mumps virus infections among previously vaccinated individuals over the past decade has prompted discussions about new strategies to mitigate the risk of future outbreaks. The decision to implement a third dose of the MMR vaccine in response to an outbreak should be considered in discussions with local public health agencies. Traditional public health measures, including the isolation of infectious persons, timely contact tracing, and effective communication and awareness education for the public and medical community, should remain key interventions for outbreak control. Maintaining high mumps vaccination coverage remains key to U.S. and global efforts to reduce disease incidence and rates of complications.

Laboratory testing and phylogenetic analysis during a mumps outbreak in Ontario, Canada

BACKGROUND

In September 2009, a mumps outbreak originated in New York and spread to Northeastern USA and Canada. This study compares the performance of different diagnostic testing methods used in Ontario and describes molecular characteristics of the outbreak strain.

METHODS

Between September 2009 and February 2010, specimens from suspect cases were submitted to Public Health Ontario Laboratory for mumps serology, culture and/or real-time reverse-transcriptase PCR (rRT-PCR) testing. rRT-PCR-positive specimens underwent genotyping at Canada's National Microbiology Laboratory. Whole genome sequencing was performed on four outbreak and three sporadic viral culture isolates.

RESULTS

Six hundred ninety-eight patients had IgM serology testing, of which 255 (37%) had culture and rRT-PCR. Among those, 35/698 (5%) were IgM positive, 39/255 (15%) culture positive and 47/255 (18%) rRT-PCR-positive. Buccal swabs had the highest rRT-PCR positivity (21%). The outbreak isolates were identical to that in the New York outbreak occurring at the same time. Nucleotide and amino acid identity with the Jeryl Lynn vaccine strain ranged from 85.0-94.5% and 82.4-99.4%, depending on the gene and coding sequences. Homology of the HN protein, the main immunogenic mumps virus protein, was found to be 94.5 and 95.3%, when compared to Jeryl Lynn vaccine major and minor components, respectively.

CONCLUSIONS

Despite higher sensitivity than serology, rRT-PCR testing is underutilized. Further work is needed to better understand the suboptimal match of the HN gene between the outbreak strain and the Jeryl Lynn vaccine strain.

Molecular characteristics of mumps viruses isolated in Taiwan from 2006 to 2016

Sixteen mumps virus (MuV) sequences collected in Taiwan between 2006 and 2016 were characterized as genotype F (n = 1), G (n = 7), H (n = 4), J (n = 2), and K (n = 2). Mumps genotype F strain was imported from China in 2008 which was in accordance with the epidemic genotype in China. The Philippines was indicated as export country of three genotype H strains in 2007-2010 and Vietnam as export country of one genotype K strain in 2016 that matched with genotypes described in previous reports. Four strains of genotype G were imported from Japan, Thailand, Malaysia and Myanmar individually indicated that genotype G spreads widely in Asia as well as in the global. In this study, mumps strains of genotype G was first reported in relation to import from Malaysia and Myanmar. Furthermore, Indonesia was referred to export MuV of genotype J in 2007 for the first time. Molecular genotyping benefits the differentiation of circulating mumps viruses and can be used to investigate the transmission pathways. The dynamic genotypes of imported cases revealed the epidemic genotypes in nearby countries.

Mumps Epidemiology and Mumps Virus Genotypes Circulating in Mainland China during 2013-2015

With the implementation of mumps virus (MuV) vaccination in the expanded program on immunization (EPI) in mainland China since 2008, the incidence of mumps has decreased, and the natural epidemic pattern of mumps has slightly changed during 2013-2015. The two epidemic peaks (April-July and November-December) became less obvious than those observed from 2004 to 2012. Children and adolescents younger than 15, particularly in the five-to-nine-year-old age group, remain the target group and should be the focus of high-quality immunization activities in mainland China. However, it was also found that the incidence and reported cases of mumps decreased in each age group during 2013-2015, particularly in the five-to-nine-year-old and ten-to-fourteen-year-old age groups. The proportion of mumps cases among adults in some provinces also increased. Unlike the changes in the epidemiological characteristics of mumps affected by vaccination, the data of MuV virology surveillance indicated that most of the MuV transmission chains have not yet been effectively interrupted, and MuV remains a natural epidemic pattern in mainland China. In the MuV virology surveillance, 194 MuV strains during 2013-2015 were isolated from 10 of 31 provinces in mainland China. Based on the phylogenetic analysis of the small hydrophobic (SH) gene, both genotype F (99.0%) and G (1.0%) were identified, and genotype F was still the predominant genotype continuously circulating in mainland China. Representative genotype F and G strains isolated in China from 1995 to 2012 were selected for further analysis. The results indicated that there were multiple transmission chains within genotype F, with no obvious geographical or time differences. The high genetic diversity of genotype F strains could be a result of the continuous transmission and evolution of the MuV in mainland China. Genotype G was also detected in four provinces in mainland China. Because of the limited epidemiological data, it was uncertain whether the genotype G MuV strains found in 2011 and 2013 were imported from other countries. Therefore, combined high-quality epidemiological and virological surveillance is necessary for mumps control; it can also be used to observe the changes in epidemiological characteristics and viral transmission of mumps over time after mumps-containing vaccine (MuCV) implementation and to provide a comprehensive epidemiological and genetic baseline for mumps elimination in mainland China.

Resurgence of mumps in Korea

Routine vaccination against mumps has markedly reduced its incidence. However, the incidence of mumps continuously has increased since 2007. In 2013, a large mumps epidemic occurred in Korea, and this epidemic is still an ongoing problem. This epidemic occurred primarily in school settings and affected vaccinated adolescents, predominantly male students. The recent resurgence of mumps is caused by multiple factors: suboptimal effectiveness of the current mumps vaccines, use of the Rubini strain vaccine, waning immunity in the absence of natural boosting due to the marked reduction in the mumps incidence, genotype mismatch between the vaccine and circulating mumps virus strains, and environmental conditions that foster intense exposures. Containment of mumps outbreaks is challenging because the sensitivity of diagnostic tests is low among vaccinees and control measures are less efficient because of the inherent nature of the mumps virus. Despite the suboptimal vaccine effectiveness in outbreak settings, maintaining the high vaccine coverage is an important strategy to prevent mumps outbreaks, given that the routine use of mumps vaccines has substantially reduced the incidence of mumps and its complications as compared with that in the pre-vaccine era. In order to control the current mumps epidemic and prevent further outbreaks, we need to better understand the dynamics of mumps among vaccinated populations and the changing epidemiology in Korea. Concerted efforts should be made to systematically monitor the immunization status of the Korean population and to improve diagnosis efficiency. Furthermore, more effective mumps vaccines need to be developed in the future.

Genetic characterization of historical epidemic mumps viruses in northern Spain, 1987-1990

The mumps virus (MuV) is genetically diverse and is divided into 12 genotypes. The World Health Organization has recommended expanding virological surveillance for MuV, and therefore molecular characterization of circulating strains (i.e. genotypes) is increasingly performed. Nevertheless, little is known about the genotypes circulating before the massive vaccination of children and adolescents. The present study analyzed the strains causing the 1988-1989 mumps epidemic in the Basque Country, northern Spain, which occurred in the early vaccination period, before the endemic circulation of mumps virus was blocked. The epidemic reached an annual incidence rate of more than 400 cases/100,000 inhabitants, and caused a large number of cases of mumps meningitis. MuV RNA was amplified from the cerebrospinal fluid of 15 infected patients during the epidemic and from three more patients affected shortly before or after this epidemic (1987, early 1988 and 1990). Genotyping of the complete small hydrophobic gene (316 nucleotides), amplified in the 18 strains, as well as of the entire hemagglutinin-neuraminidase gene (1749 nucleotides), amplified in four strains, assigned all strains to genotype K, a genotype infrequently detected at present. Although the putative HN protein sequence differed by 4.8-5.5% in relation to Jeryl Lynn 5 strain (the main strain used in the vaccination program in this region), the vaccine was effective, and dramatically reduced the incidence of mumps over the following years. The presence of genotype K strains in Spain in the 1980s, together with their contemporary detection in Scandinavia, suggests that this genotype could have caused the Spanish epidemic and was also circulating widely in Europe at that time.

Mumps vaccine effectiveness in highly immunized populations

The aim of the study was to investigate effectiveness of mumps MMR component in communities with high MMR coverage. Outbreak-related cases of mumps born between 1995 and 2005 notified to Navarre and Catalonia public health services during the period 2005-2007 were studied. Vaccine effectiveness (VE) and their 95%CI were calculated using the screening method. Of 47 confirmed, 85.1% immunized with at least one dose (1MMR) and 44.9% with two (2MMR). Estimated VE was 85.4% (95%CI: 67.3-93.4) for 1MMR and 88.5% (95%CI: 78.1-93.9) for 2MMR. High 2MMR coverage, improved confirmation techniques and further VE studies with all confirmed cases are needed to prevent further outbreaks.

Circulation of mumps virus genotypes in Spain from 1996 to 2007

Although the WHO recommends the use of genotyping as a tool for epidemiological surveillance for mumps, limited data on mumps virus (MV) genotype circulation that may be used to trace the patterns of virus spread are available. We describe the first complete series of data from Spain. The small hydrophobic region was sequenced from 237 MV-positive samples from several regions of Spain collected between 1996 and 2007. Six different genotypes were identified: A, C, D (D1), G (G1, G2), H (H1, H2), and J. Genotype H1 was predominant during the epidemic that occurred from 1999 to 2003 but was replaced by genotype G1 as the dominant genotype in the epidemic that occurred from 2005 to 2007. The same genotype G1 strain caused concomitant outbreaks in different parts of the world (the United States, Canada, and the United Kingdom). The remaining genotypes (genotypes A, C, D, and J) appeared in sporadic cases or small limited outbreaks. This pattern of circulation seems to reflect continuous viral circulation at the national level, despite the high rates of vaccine coverage.

Mumps outbreaks in vaccinated populations: are available mumps vaccines effective enough to prevent outbreaks?

Increased reports of mumps in vaccinated populations prompted a review of the performance of mumps vaccines. The effectiveness of prior vaccination with 1 dose of vaccine ranged from 72.8% to 91% for the Jeryl Lynn strain, from 54.4% to 93% for the Urabe strain, and from 0% to 33% for the Rubini strain. Vaccine effectiveness after 2 doses of mumps vaccine was reported in 3 outbreaks and ranged from 91% to 94.6%. There was evidence of waning immunity, which is a likely factor in mumps outbreaks, aggravated by possible antigenic differences between the vaccine strain and outbreak strains. Inadequate vaccine coverage or use of the Rubini vaccine strain accounted for the majority of outbreaks reviewed; however, some outbreaks could not be prevented, despite high vaccination coverage with 2 doses of the Jeryl Lynn vaccine strain. Our findings indicate the need for more-effective mumps vaccines and/or for review of current vaccination policies to prevent future outbreaks.

Internationally adopted children: what vaccines should they receive?

It is of paramount importance to know the vaccination status in internationally adopted children, so that they can be correctly immunized. This study ascertains the seroprotection rate for vaccine-preventable diseases and the validity of the immunization cards in 637 adopted children. The absence of the immunization card (13% of children) correlated with a poor global vaccine protection. Children with immunization records (87%) had a better global seroprotection but the information obtained from the card did not accurately predict seroprotection for each particular antigen. The best variable to predict the status of seroprotection was the country of origin. The highest rate of protection was found in children from Eastern Europe and, in descending order, India, Latin America, China and Africa. General recommendations for immunization of internationally adopted children are difficult to establish. Actions for vaccination have to be mainly implemented on the basis of the existence of the immunization card and of the country of origin.

Molecular identification of two genotypes of mumps virus causing two regional outbreaks in Asturias, Spain

BACKGROUND

In spite of universal vaccination, several sporadic cases of mumps infection, which could produce outbreaks, are detected every year in different countries.

OBJECTIVE

Mumps virus strains causing two regional outbreaks in Asturias (Spain) were phylogenetically characterized.

STUDY DESIGN

Mumps virus strains, which were detected in samples from patients belonging to two regional outbreaks in Asturias, were characterized by sequencing of the SH gene and further alignment to homologous sequences of representative strains of the different mumps genotypes.

RESULTS

Two different strains (Ast/SP02 and Ast/SP07) were isolated. Sequence analysis revealed that while Ast/SP02 belonged to genotype H, Ast/SP07 was phylogenetically close to UK02-19, a reference strain for a new genotype. Both strains belonged to different genotypes from those used in the vaccination (Jeryl-Lynn strain is genotype A).

CONCLUSION

Mumps virus strains different from those used in vaccination program can cause mumps outbreaks even in vaccinated patients.

Variability of hemagglutinin-neuraminidase and nucleocapsid protein of vaccine and wild-type mumps virus strains

The mumps virus (MuV) molecular evolution is characterized by the co-circulation of numerous distinct strains. Standardized phylogenetic analyses based on the nucleotide sequences of the SH gene are important for mumps surveillance, but lack the information regarding antigenic properties. So far, the location of antigenic epitopes has been determined for two MuV proteins, the hemagglutinin-neuraminidase (HN) and the nucleocapsid (N) protein. We performed multiple sequence comparisons of putative HN and N protein sequences in order to describe their diversity and plasticity, and to determine the level of similarity between vaccine and wild-type strains. The results of full-length HN or N protein phylogeny showed that MuV strains form a number of differing clades which are in concordance with grouping obtained by standard MuV genotyping. When vaccine strains are compared to all wild-type strains, the highest mean percentage of amino acid differences in both HN and N protein analysis was found for Jeryl Lynn 5 and Jeryl Lynn 2 strains while the lowest value was obtained for Leningrad-3 and L-Zagreb strains. When only 3 antigenic regions of the HN protein, comprising 45 amino acids in total, were investigated, the diversity is considerably diminished: 51.5% of all putative HN proteins show identical sequences (including those of vaccine strains L-Zagreb, Leningrad-3, Hoshino and Urabe). Another 26.5% proteins (including Miyahara vaccine strain) differ in only one amino acid, while the others differ in two to five amino acids from the most common sequence. Jeryl Lynn 2 and Jeryl Lynn 5 strains differ in four amino acids each. N protein antigenic sites have been mapped within its hypervariable C-terminus. Our results indicate that there might be genotype-specific amino acids residing in this antigenic region. The results of our study present the background information for investigations of MuV heterogeneity and antigenic diversity.

Sensitivity and specificity of immunoglobulin G titer for the diagnosis of mumps virus in infected patients depending on vaccination status

The aim of the study was to evaluate the usefulness of serological detection of mumps IgM and titration of IgG in patients with acute parotitis according to their vaccination status. The detection of mumps virus RNA in saliva by RT-PCR was used as reference. 116 patients (109 of them previously vaccinated) with mumps RT-PCR-negative results and 21 (19 vaccinated) with mumps RT-PCR-positive results were studied. Mumps-specific IgM and IgG were assayed by EIA (Enzygnost, Dade Behring, Germany). IgM results were expressed as positive or negative. For IgG, several cut-offs were calculated using receiver operating characteristic (ROC) curves. Seven RT-PCR-positive and five RT-PCR-negative patients showed IgM-positive results (sensitivity 33.3% and specificity 95.7%). Among vaccinated patients, the sensitivity and specificity of IgM were 26.3% (5/19) and 99.1% (108/109). For IgG, a titer of 5,000 in all the patients showed a sensitivity of 76.2% (16/21) and a specificity of 83.6% (97/116). In vaccinated patients, the corresponding figures for this cut-off were 84.2% (16/19) and 83.5% (91/109), respectively. Although IgM detection against mumps is highly specific, its sensitivity is very low in immunized subjects. In this group, the titration of IgG could serve as an additional diagnostic tool.

Non-preventable mumps outbreaks in schoolchildren in Catalonia

Various doses of the combined MMR vaccine containing the Rubini mumps strain were distributed in Catalonia in 1994 and 1995. We studied outbreaks of mumps reported from 1997 to 2002 to determine the possible involvement of this vaccine in the appearance of non-preventable mumps outbreaks. A total of 17 mumps outbreaks were declared in the period 1997-2000, 14 of which were in schoolchildren. In 11, it was determined that children were correctly vaccinated. Of these, 10 were non-preventable outbreaks. 66% of cases investigated had ages which coincided with vaccination in the period 1994-1996, during which the MMR vaccine containing the Rubini mumps strain was administered. In Catalonia, during the period 1997-2000, at least two-thirds of mumps cases in schoolchildren could be explained by vaccination with the combined MMR vaccine containing the Rubini strain, which has also been associated with mumps outbreaks amongst vaccinated people in other countries.

Mumps virus strains isolated in Croatia in 1998 and 2005: Genotyping and putative antigenic relatedness to vaccine strains

Two mumps virus strains 9218/Zg98 and Du/CRO05 were isolated in two locations in Croatia in 1998 and 2005, respectively. Genetic characterization of these temporally distinct mumps virus isolates was carried out in order to determine their genotype and putative antigenic relatedness to mumps virus vaccine strains. Sequence analysis of the small hydrophobic (SH) gene revealed that isolate 9218/Zg98 shows less than 95% of similarity to any reference strain, thus representing a potential reference strain for a new genotype. Isolate Du/CRO05 clearly belongs to genotype G with the 97% of homology to the reference strain Glouc1/UK96. When compared to each other, the two Croatian strains have extremely low level of homology of only 89% indicating no relatedness between them. Putative antigenic properties of the HN protein of these two isolates were compared to different vaccine strains. The results reveal a higher level of homology of antigenic determinants to non-A genotype vaccine strains than to A genotype vaccine strain.

Detection of secondary mumps vaccine failure by means of avidity testing for specific immunoglobulin G

The aim of this study was to discriminate between primary and secondary vaccine failure in children with mumps using IgG avidity testing. Thirty-nine serum samples from children with mumps, confirmed by specific IgM, were studied. The patients were grouped according to their immunization status. The secondary immune response was defined by IgG with an avidity index >32%. A secondary response in infected children previously immunized was considered as a secondary vaccine failure. Vaccinated children presented higher IgG titers and IgG avidity than unvaccinated children. The proportion of secondary immune responses in unvaccinated patients was lower than that obtained in previously vaccinated infected patients. Avidity testing can be a useful tool to detect secondary vaccine failure in mumps.

Molecular identification of mumps virus genotypes from clinical samples: standardized method of analysis

A sensitive nested reverse transcription-PCR assay, targeting a short fragment of the gene encoding the small hydrophobic protein (SH gene), was developed to allow rapid characterization of mumps virus in clinical samples. The sensitivity and specificity of the assay were established using representative genotypes A, B, C, D, E, and F. Mumps virus RNA was characterized directly from cerebrospinal fluid (CSF) samples and in extracts of mumps virus isolates from patients with various clinical syndromes. Direct sequencing of products and subsequent phylogenetic analysis enabled genetic classification. A simple web-based system of sequence analysis was established. The study also allowed characterization of mumps virus strains from Argentina as part of a new subgenotype. This PCR assay for characterization of mumps infections coupled to a web-based analytical program provides a rapid method for identification of known and novel strains.

Phylogenetic analysis of clinical mumps virus isolates from vaccinated and non-vaccinated patients with mumps during an outbreak, Switzerland 1998-2000

During the past decade mumps outbreaks have occurred in several European countries with universal vaccination programs probably due to poor efficacy of the Rubini vaccine strain. However, the evolution of vaccine escape mutants has also been considered. A phylogenetic analysis was undertaken on 69 clinical mumps isolates obtained from 39 vaccinated and 22 non-vaccinated mumps cases (and six cases with unknown vaccination status) during an outbreak in 1998-2000. Two major strain clusters (SWI-H, SWI-C) with two subgroups each (SWI-H1/2, SWI-C1/2) were identified, which belonged to genotypes C and H. No association between viral clusters and vaccination status or a specific vaccine strain (Jeryl-Lynn or Rubini) was found. Cluster SWI-C1 occurred more frequently in the Western part of Switzerland (P < 0.001). Isolates causing complicated disease tended to cluster more frequently with SWI-H1 (P = 0.11). Wild-type strains homologous or similar to the Rubini vaccine strain (isolated in Switzerland in 1974) were no longer circulating. Therefore, there was no evidence for vaccine escape mutants. Strain redistribution may have occurred during the past decades. Continuous monitoring of circulating mumps virus populations is needed.

Genetic characterization of a mumps virus isolate during passaging in the amniotic cavity of embryonated chicken eggs

The aim of this study was the molecular characterization of a historical mumps isolate (an alleged individual sample). After RNA extraction and cDNA synthesis, selective nested PCR amplification with specific primers, automated DNA sequencing and RFLP analyses were performed. The relative ratios of the detected virus sequences were determined by GeneScan electrophoresis. Phylogenetic tree based on the 316 nucleotide region of the SH gene of the mumps virus was generated by the neighbor-joining method. Results obtained by the described molecular approach show: (a) there are two mumps virus variants, A and B, detected in the fourth passage of wild type virus in the amniotic cavity of embryonated chicken eggs (ECE); (b) variants A and B belong to different genotypes; (c) variants A and B differ in the HN and NP genes which code for amino acid sequences comprising immunogenic epitopes; (d) variant B contains one or more minor variants. We discuss whether the observed differences between the two variants are a consequence of natural heterogeneity or of laboratory contamination in the early passages.