The investigation and spatio-temporal analysis of first importation associated D8 genotype measles case in a child, Shandong Province, 2023
10.3760/cma.j.cn112150-20240513-00383
- VernacularTitle:2023年山东省1例儿童输入相关性D8基因型麻疹的现场调查及其时空关联分析
- Author:
Suting WANG
1
;
Yao LIU
;
Qing XU
;
Shuaizhi GUO
;
Dongchen LIU
;
Aiqiang XU
;
Zexin TAO
;
Li ZHANG
Author Information
1. 山东省疾病预防控制中心免疫规划所，济南 250014
- Publication Type:Journal Article
- Keywords:
Importation associated measles;
Child;
Genotype D8;
Avidity;
Spatio-temporal analysis
- From:
Chinese Journal of Preventive Medicine
2025;59(4):451-457
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To analyze the epidemiological, etiological characteristics and transmission of an imported D8 genotype measles case in a child in Shandong Province, August 2023.Methods:A study was conducted on a measles case and 16 contacts in Shandong Province in August 2023. Field epidemiological surveys, including recent exposure and immunization history, were conducted. Serum and throat swab samples were collected from all 16 subjects. Measles IgM and IgG antibody levels and avidity were measured by ELISA, while virus detection and genotyping were performed using fluorescence quantitative PCR and RT-PCR. Genetic evolutionary analysis of the obtained sequences was conducted using MEGA and Beast software.Results:The case was an 11-year-old boy, a fifth-grade student, who developed symptoms on August 28, 2023. A total of five close contacts were investigated, including three family members (grandfather, father and sister) and two playmates. Additionally, 11 classmates who had close contact with the case′s sister during the infectious period (within five days after the rash onset) were also investigated. Among the 16 serum samples tested, only one case was positive for IgM, while the other 15 samples were negative for IgM. The results of the serum antibody avidity test showed that among the 16 serum samples, 14 were positive for IgG. Of these, eight had a relative avidity index >55%, indicating high-avidity antibodies; one had a relative avidity index <45%, indicating low-avidity antibodies; and five had an avidity index between 45% and 55%. The IgG detection OD values for the case′s sister and grandfather were higher than those of the other contacts. Based on the vaccination history of the subjects and the results of IgM and IgG tests, it was preliminarily determined that the case had a recent wild-type measles virus infection. The case′s sister and grandfather had a history of measles wild-type virus infection, while the high-avidity antibodies in the other contacts were likely induced by the measles vaccine. The results of the pharyngeal swab tests showed that only the case was positive for measles virus nucleic acid, while the remaining 15 samples were negative for measles virus. The genetic evolutionary analysis revealed that the viral sequence of this case (Mvs/Shandong.CHN/38.23) had a 100% homology with the Hong Kong strain sequence from August 2023. It belonged to a different transmission chain from the D8 genotype strains that appeared in Shandong Province between 2018 and 2019, with sequence homology ranging from 98.0% to 98.8%. The sequence homology within the transmission chain of this case was between 99.1% and 100%. The evolutionary rate of this transmission chain was approximately 8.38×10 -3 sub/site/year, and the most recent common ancestor was estimated to have emerged around the year 2011. Conclusion:This case is the first imported D8 genotype measles case in Shandong Province. There is no spatio-temporal correlation between this case and adult cases of D8 genotype imported from Shandong Province in 2018-2019, indicating a new D8 genotype imported epidemic.
