Molecular Epidemiology of Rubella Virus Strains Detected Around the Time of the 2012-2013 Epidemic in Japan

Shedding of rubella virus in postsymptomatic individuals; viral RNA load is a potential indicator to estimate candidate patients excreting infectious rubella virus

BACKGROUND

Since the first isolation of rubella virus (RuV) in 1962, comprehensive data regarding the quantitative evaluation of RuV shedding remain unavailable. In this study, we evaluated the shedding of viral RNA and infectious virus in patients with acute RuV infection.

STUDY DESIGN

We analyzed 767 specimens, including serum/plasma, peripheral blood mononuclear cells (PBMCs), throat swabs, and urine, obtained from 251 patients with rubella. The viral RNA load and the presence of infectious RuV were determined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and virus isolation.

RESULTS

Virus excretion peaked 0-2 days after rash onset and decreased over time. The median viral RNA load dropped to an undetectable level on day 3 after rash onset in serum/plasma, day 2 in PBMCs, days 10-13 in throat swabs, and days 6-7 in urine. Infectious virus could be isolated for up to day 2 after rash onset in serum/plasma, day 1 in PBMCs, days 8-9 in throat swabs, and days 4-5 in urine. The minimum viral RNA load that allowed virus isolation was 961 copies/mL in serum/plasma, 784 copies/mL in PBMCs, 650 copies/mL in throat swabs, and 304 copies/mL in urine. A higher viral RNA load indicated a higher likelihood of the presence of infectious virus.

CONCLUSION

These findings would contribute to improve algorithms for rubella surveillance and diagnosis. In addition, this study indicates that the results of RT-qPCR enable efficient rubella control by estimating candidate patients excreting infectious virus, which could help prevent viral transmission at an early stage and eliminate rubella ultimately.

Phylogenetic analysis of congenital rubella virus from Indonesia: a case report

BACKGROUND

Rubella is a common inherited infection resulting in congenital cataracts and a significant cause of permanent vision loss in developing countries. In 2016, Indonesia had the highest number of congenital rubella syndrome (CRS) cases globally. Here, we report the first genotype of the rubella virus extracted from the eye lens from a child with congenital cataracts due to CRS.

CASE PRESENTATION

A female neonate was delivered by an elective caesarean delivery with normal birth weight at term from a 24-year-old mother in the rural setting. The baby presented with bilateral congenital cataracts, small-moderate secundum atrial septal defect, severe supravalvular pulmonary stenosis, and profound bilateral hearing loss. She also had microcephaly and splenomegaly. The patient's serology showed persistent positive IgG for rubella virus at the age of four years and four months. Following extraction during cataract surgery, viral detection of the lenses identified the presence of rubella. Phylogenetic analysis confirmed that the virus was grouped into genotype 1E.

CONCLUSIONS

Our study reports the first phylogenetic analysis of the rubella virus extracted from the eye lens of a child with CRS in Indonesia. The detection of the rubella virus from eye lenses is remarkably promising. Our findings also emphasize the importance of molecular epidemiology in tracking the origin of rubella infection toward achieving virus eradication.

Epidemiology of Congenital Rubella Syndrome Related to the 2012-2013 Rubella Epidemic in Japan

This study assessed the epidemiological characteristics of 45 congenital rubella syndrome cases in Japan following the 2012-2013 rubella epidemic. Rubella still poses significant health burdens and the uptake of rubella-containing vaccines among women of childbearing age should be improved.

Importation and circulation of rubella virus lineages 1E-L2 and 2B-L2c between 2018 and 2021 in China: Virus evolution and spatial-temporal transmission characteristics

To better understand the importation and circulation patterns of rubella virus lineages 1E-L2 and 2B-L2c circulating in China since 2018, 3,312 viral strains collected from 27 out of 31 provinces in China between 2018 and 2021 were sequenced and analyzed with the representative international strains of lineages 1E-L2 and 2B-L2c based on genotyping region. Time-scale phylogenetic analysis revealed that the global lineages 1E-L2 and 2B-L2c presented distinct evolutionary patterns. Lineage 1E-L2 circulated in relatively limited geographical areas (mainly Asia) and showed geographical and temporal clustering, while lineage 2B-L2c strains circulated widely throughout the world and exhibited a complicated topology with several independently evolved branches. Furthermore, both lineages showed extensive international transmission activities, and phylogeographic inference provided evidence that lineage 1E-L2 strains circulating in China possibly originated from Japan, while the source of lineage 2B-L2c isolated since 2018 is still unclear. After importation into China in 2018, the spread of lineage 1E-L2 presented a three-stage transmission pattern from southern to northern China, whereas lineage 2B-L2c spread from a single point in western China to all the other four regions. These two transmission patterns allowed both imported lineages to spread rapidly across China during the 2018-9 rubella epidemic and eventually established endemic circulations. This study provides critical scientific data for rubella control and elimination in China and worldwide.

Improved diagnostic and multiplex RT-qPCR for detecting rubella viral RNA

An examination of the nucleic acid sequence alignment of 48 full-length rubella virus genomes revealed that the 5' terminus of the genome is more conserved than the commonly used detection windows for rubella virus RNA located in the E1 protein coding region, suggesting that the 5' terminus could be a target for improving detection of all rubella virus genotypes. Two candidate primer sets were tested and the window between nucleotides (nts) 98 and 251 was found to have the greatest analytical sensitivity for detection of different genotypes. The new method had a limit of detection of four copies of rubella RNA per reaction with high specificity. The average coefficient variation of Ct was 2.2%. Concordance between the new method and currently used method, based on testing 251 clinical specimens collected from a rubella outbreak, was 99.4%. The assay was further improved upon by the incorporation of detection of both rubella virus RNA and mRNA from a cellular reference gene in a multiplex format. The multiplex format did not reduce the sensitivity or the reproducibility of rubella RNA detection and, of 60 specimens tested, the concordance between the single target and multiplex assays was 85.0%. To assess the utility of the multiplex assay for molecular surveillance, 62 rubella IgM positive serum samples from a rubella outbreak were tested, and eleven tested positive using the multiplex method while none were positive using the method targeting E1. These results show that the assay based on the new detection window near the 5' terminus of the genome can improve the detection of rubella virus for the purpose of molecular surveillance and case confirmation, with the added benefit of improved efficiency due to multiplexing.

Changes in awareness and knowledge concerning mother-to-child infections among Japanese pregnant women between 2012 and 2018

This study aimed to investigate the long-term changes in awareness of and knowledge about mother-to-child infections across 6 years in Japan. A questionnaire survey was conducted at our facility from October 2012 to January 2018, and the study periods were divided into 4 phases comprising 16 months each. A multiple-choice questionnaire assessed participants’ awareness of the following 13 pathogens of mother-to-child infections: cytomegalovirus (CMV), Toxoplasma gondii (T. gondii), hepatitis B virus, rubella virus, herpes simplex virus, parvovirus B19, hepatitis C virus, human immunodeficiency virus, human T cell leukemia virus type-1, measles virus, varicella-zoster virus, Chlamydia trachomatis, and Treponema pallidum. For the selected four pathogens (i.e., CMV, rubella virus, T. gondii, and parvovirus B19), the questionnaire also evaluated participants’ knowledge of transmission routes, the most susceptible time of infection that could yield severe fetal disease during pregnancy, the maximum frequency of fetal infection in cases of maternal infection, and methods to prevent maternal infection. In total, 1433 pregnant Japanese women were included in this study. There was no secular change in awareness of the pathogens concerning mother-to-child infections over time, and we also clarified that the detailed knowledge of the four pathogens of typical mother-to-child infections did not improve. Since knowledge about methods to prevent maternal infection is still insufficient for all pathogens, further advocacy is required to prevent mother-to-child infections.

Rubella outbreak among workers in three small- and medium-size business establishments associated with imported genotype 1E rubella virus-Shizuoka, Japan, 2015

On 12 February 2015, a local health department (LHD) in Shizuoka prefecture identified two reported rubella cases in its jurisdiction as employees of the same company. As other employees at the company resided both inside and outside of the health department's jurisdiction, it began collaborating with two additional LHDs and the National Institute of Infectious Diseases to investigate and respond to the outbreak, which subsequently identified cases in two additional companies. We obtained epidemiological, clinical, and outbreak response information from the national epidemiological surveillance of infectious disease system's database, the local health departments, and the associated companies. One specimen for genetic sequencing was collected from each of the three companies. The outbreak included a total of twenty-five cases, with seventeen confirmed and eight probable cases from three companies. Among them, 24 (96%) were male, 22 (88%) were employees of one company (Company X), and none had rubella vaccination history. The median age was 45 years (interquartile range: 40-51). Epidemiological information did not reveal the source of infection nor transmission route. All rubella viruses sequenced from the three specimens were classified into genotype 1E. The nucleotide sequences in the 739 bp-window region were completely identical in two specimens, with only one nucleotide difference in the third specimen. According to phylogenetic analysis, these strains were closely related to the Southeast and East Asian lineage. This rubella outbreak at three companies, ranging in size from small- to medium-size, in Japan occurred among unvaccinated employees aged at least 30 years, most of whom were male. Virologic analyses suggest all cases were infected with the same viral strain imported from Southeast Asia. Similar to these companies, most employees at small- and medium-size businesses in Japan are males with no vaccination history for rubella, which poses a serious risk for associated cases of congenital rubella syndrome (CRS).

Strategies for elimination of rubella in pregnancy and of congenital rubella syndrome in high and upper-middle income countries

Rubella infection generally leads to mild symptoms; otherwise, in pregnant women it can cause severe damages. The only way to prevent rubella is vaccine. Before the introduction of the vaccine, up to 4 babies in 1000 live births were born with CRS.

This work aims to review the most important strategies for the elimination of CRS in upper and high-income countries.

Papers were selected through a PubMed search up to January 2019, using keywords rubella, congenital rubella syndrome and epidemiology. Articles published in the last 12 years and referred to upper income and high-income countries in title or abstract were included.

Sixty-five papers were selected dealing with one or more of the following strategies: increasing of rubella vaccination coverage in childbearing age women, males, immigrants; exploitation of all appropriate occasions; improving of rubella surveillance.

Despite numerous suggestions and indications for valid strategies to eliminate rubella in pregnancy and congenital rubella syndrome, a practical application is often missing.

Modelling a Supplementary Vaccination Program of Rubella Using the 2012⁻2013 Epidemic Data in Japan

From 2012-2013, Japan experienced a major epidemic of rubella, involving a total of 12,614 rubella cases and 45 confirmed cases of congenital rubella syndrome (CRS). One of the contributory factors in this outbreak may have been that the majority of adult males remained unvaccinated. To plan for a supplementary immunization program (SIP) to elevate the herd immunity level, it is critical to determine the required amount of vaccine and identify the target age groups among males for the SIP. The present study aimed to answer these policy questions, employing a mathematical model and analyzing epidemiological datasets from 2012-2013. Our model allowed us to reconstruct the age- and sex-dependent transmission patterns, and the effective reproduction number during the exponential growth phase in 2013 was estimated to be 1.5. The computed next-generation matrix indicated that vaccinating adult males aged from 20-49 years in 2013, using at least 17 million doses, was considered essential to prevent a major epidemic in the future. The proposed model also indicated that, even with smaller doses of vaccine, the SIP in adult males could lead to a substantial reduction in the incidence of rubella, as well as CRS. Importantly, the present study endorses a substantial background risk of observing another major epidemic from 2018-2019, in which cases may be dominated by adult males aged from 25-54 years, that is, our identified age groups plus a five-year time lag from 2013 to 2018.

Rubella Virus Genotype 1E in Travelers Returning to Japan from Indonesia, 2017

Although rubella is epidemic in Indonesia, the phylogenetic profile of circulating rubella virus strains has not been clarified. In 2017, rubella virus was detected in 2 travelers who returned from Indonesia to Japan. These strains were classified into genotype 1E lineage 2, which may be an indigenous strain in Indonesia.

Predicting congenital rubella syndrome in Japan, 2018-2019

OBJECTIVES

A rubella epidemic has been ongoing in Japan since August 2018. In the present study, we aimed to predict the likely size of a congenital rubella syndrome (CRS) epidemic during 2018-19.

METHODS

The expected number of CRS cases was estimated using an integral equation based on age-specific incidence of rubella among adult women, the time delay from gestational age of infection to diagnosis of CRS, and distribution of the mothers' age at delivery. We used epidemic data during 2012-14 to parameterize the model and applied this in the prediction for 2018-19.

RESULTS

In analyzing the 2012-14 epidemic data, the mean delay from the mother's infection to diagnosis was estimated at 24.2weeks (95% confidence interval (CI): 20.7, 28.1). Applying the parameterized model, together with the more than 480 rubella cases in women in 2018 as well as delayed mother's age at delivery in 2017, we determined that the expected number of CRS cases would be 9.7 (95% CI: 6.5, 12.5) cases. As the epidemic is ongoing, the cumulative number of CRS cases could potentially reach 96.8 (95% CI: 65.3, 125.5) cases, if rubella cases in adult women rose to 10 times the number by week 49 in 2018.

CONCLUSIONS

CRS is expected to occur an average of 24weeks following the mother's infection with rubella virus. Accounting for an increase to 650 cases in women by week 5 in 2019, the expected number of CRS cases during 2018-19 has already exceeded 13 cases, as of week 5 in 2019.