Resurgence of measles virus infection in an eliminated country, Sri Lanka

Objective:To describe the situation of measles in Sri Lanka from May to November,2023 and to define the role of virology laboratory towards case confirmation and epidemiological and genetic characterization of the outbreak.Methods:This retrospective study analyzed all samples tested for measles from 1st of May to 30th of November,2023 at National Measles Rubella Laboratory,Sri Lanka.According to the World Health Organization(WHO)algorithm,serum and oropharyngeal/nasopharyngeal swabs were tested with WHO recommended kits for anti-measles IgM and measles virus specific RNA,respectively.Selected RNA positive samples were sequenced at reference laboratory,India.Analysis of sequencing data and construction of phylogenetic tree were carried out at National Measles Rubella Laboratory.Data was analyzed using descriptive statistics.Results:Of the total 1132 serum samples and 497 oropharyngeal/nasopharyngeal swabs from 1326 patients,657(49.5%)patients were confirmed as measles by anti-measles IgM,measles virus specific RNA or both.Males(55.6%,n=365)and the age group from>20 to≤30 years(33.0%,n=217)predominated positive patients.All provinces reported measles positive cases.All samples sequenced(100%,n=42)were genotype D8 with 95.2%(n=40)bearing Victoria.Australia origin.Conclusions:We described resurgence of measles in an eliminated country,confirming the genotype to be D8,one of the two genotypes currently circulating globally.Further,the study strongly convinced the importance of a strengthened virological surveillance system in an eliminated country,despite its eliminated status.

Multinational Measles Outbreak in Post-Elimination Era,Involves Three Countries of North America and a European Country in a Short Transmission Chain

Background: Four measles cases in Canada and one in the United States are linked to international importation of measles in Playa del Carmen, Quintana Roo, Mexico. Objective: To describe characteristics of transmission and not spillover to local population in Mexico. Material and Methods: The outbreak investigation was based on active search of cases and in the rapid monitoring of vaccination coverage in children aged 1 - 7 years old. Laboratory confirmation by Enzyme-Linked Immunosorbent Assay (ELISA) and molecular detection by Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) assay in throat swab and urine were done. Results: One transmission chain with three generations of cases was identified. The primary case was a 9-year-old boy who was infected in Wales, UK. His sisters aged 7 and 15 years old respectively, were the first generation of cases in Mexico. The second generation was related to the imported cases, and affected two Canadian tourists and an American woman aged 39 years old. A third generation occurred in Canada and affected an infant of 15 months of age and his sister aged 4 years old. The genotype D8 which was circulating in UK was identified in these patients. One probable case was detected in Quintana Roo, but was discarded by laboratory testing. The coverage with at least one dose of Measles-Mumps-Rubella (MMR) vaccine ranged from 95% to 99.5%. Conclusion: International travelers with no history of vaccination are at risk of acquiring measles even in countries that have interrupted endemic transmission. The high immunization coverage of measles containing vaccine could explain the absence of cases in Mexican population. Highlights: Multinational measles outbreak in a country without endemic transmission. The findings exhibit the importance of immunization in international travelers in the post-elimination era.