Molecular epidemiology of measles virus infection in Shanghai in 2000-2012: the first appearance of genotype D8

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.

Epidemiological Investigation and Virus Tracing of a Measles Outbreak in Zhoushan Islands, China, 2019

Background: Measles transmissions due to case importations challenge public health systems globally and herd immunities in all countries. In 2019, an imported measles case and its subsequently outbreak was found in the Zhoushan Islands. Here, the process of epidemiological investigation and virus tracing were summarized to provide references for the prevention and control of measles in the future. Materials and methods: The data on the demographic, epidemiological, and clinical manifestation of measles cases in this outbreak were collected. The 450 bp fragments of the measles virus (MeV) N gene were amplified and sequenced. The genome of the first imported case was further isolated. Then, the maximum-likelihood and time-scaled phylogenetic analysis was conducted. Results: A total of 28 measles cases were confirmed. Their onsets were between March 13 and May 18, 2019. The first patient was from the Ukraine. He was confirmed at the Fever Clinic in Zhoushan hospital on March 15, 2019 and at the same time, another patient had visited the hospital due to another illness and 10 days later, this second case had onset (March 25, 2019). The epidemic curve shows sustained community transmission. The majority of the following cases (19/26) were clustered on the Donggang street which was close to where the second case worked. The 22 measles virus strains successfully isolated from this outbreak all belonged to the D8.2a sub-cluster and clustered with the KY120864/MVs/GirSomnath.IND/42.16/[D8] which was the predominant genotype in the Ukraine during 2018-2019. The analysis of the complete D8 genotype genome pointed to the fact that this prevailing strain originated from India in 2015 and its substitution rate was estimated as 6.91 × 10^-4 (5.64-7.98 × 10^-4) nucleotide substitutions/site/year. Conclusion: This outbreak was caused by an imported case from the Ukraine. There was a possible nosocomial infection between the first case and the second case. Then, the second case played an important role in the spread of virus due to her occupation. The molecular phylogenetic analysis could help to track the origin of the virus. Increasing and maintaining the high level of vaccination coverage (≥95%) and an efficient response to imported cases are essential to prevent and control the recurrence and outbreak of measles virus.

Molecular characterization of measles viruses in China: Circulation dynamics of the endemic H1 genotype from 2011 to 2017

Due to the Expanded Program on Immunization (EPI) and supplementary immunization activities (SIAs) in China, the incidence of measles in China has decreased extensively. The incidence reached its lowest levels in contemporary history in 2012 and 2017, with incidence rates of 4.6 and 4.3 per million population, respectively. However, more than 147,000 measles cases were reported from 2013 to 2016. Furthermore, the proportions of cases in infants < 8 months and adults have been increasing since 2013, representing a considerable challenge for measles elimination in China. A total of 14,868 measles viruses were isolated from confirmed measles cases from 2011 to 2017, of which 14,631 were identified as the predominant endemic genotype, H1; 87 were identified as genotype A viruses that were vaccine associated strains; and 150 were identified as non-H1 genotype viruses. The non-H1 genotype viruses included 62 D8 viruses, 70 D9 viruses, 3 D11 viruses, 14 B3 viruses, and 1 G3 virus, which were identified as imported or import-related viruses that caused sporadic cases or small outbreaks. Most of the transmission chains detected during the period 2011–2012 were interrupted and were followed by many new transmission chains of unknown origin that spread, causing a large measles resurgence in China during 2013–2016. After 4 years of measles resurgence and continuous implementation of the routine immunization program and SIAs, the population immunity reached a sufficiently high level to interrupt most of the transmission chains; only a few strains survived, which continued to be sporadically detected in China in 2017. In the present study, the results from the combined epidemiological and molecular virological data demonstrated the great progress towards measles elimination in China by the further analysis of circulation dynamics for the endemic H1 genotype measles virus from 2011 to 2017. And this study accumulated critical baseline data on circulating wild-type measles viruses in China and provides comprehensive information to the world. These comprehensive baseline data provide evidence to support measles elimination in the future, not only in China but also in other countries worldwide. In addition, the information will be very useful to other countries for tracing their sources of measles cases and for identifying transmission links, which can help prevent potential measles outbreaks.

The first outbreak of measles virus caused by imported genotype D8 in Jiangsu province of China

Here we reported the outbreak of measles cases caused by the genotype D8 measles virus for the first time in Jiangsu province in China, which was possibly imported by a foreign student from Laos. Throat swab specimens were collected, and used to isolate virus. 634-bp fragment of the N gene and 1854-bp fragment of H gene were amplified by reverse transcription-PCR and sequenced, respectively. Phylogenetic results indicated that they belonged to genotype D8 measles virus. Further epidemiology investigation showed that the adults with D8 measles virus infection did not receive measles vaccine before having measles. In China, almost all D8 genotype MeV only infected those population without receiving measles vaccine immunization. Therefore, it is still necessary to implement the supplement activity of measles immunization target adult with immunity gap.