Epidemiological and Molecular Genetic Monitoring of Measles in Kazakhstan in 2023

1. Introduction: Measles virus remains one of the main causes of childhood morbidity and mortality, posing a serious threat to most countries. Since March 2023, measles incidence rates have been growing in Kazakhstan, with the disease registered in previously unvaccinated, incompletely or untimely vaccinated children and adults representing a wide unimmunized stratum of the population. Objective: To conduct epidemiological and molecular genetic monitoring of measles viruses causing the increase in disease incidence in Kazakhstan in 2023. Materials and methods: The analysis of measles incidence in the Republic of Kazakhstan in 2023 was based on state statistics. In order to genotype circulating measles strains, we took 69 clinical urine samples and performed Sanger sequencing of the C-terminal region of the N-gene. Results: In 2023, 29,731 measles cases were registered in Kazakhstan, the incidence rate being 149.95 per 100 thousand population. Most of the cases were children aged 1 to 4 years – 43.3 %, followed by children aged 5–14 years – 19.9 % and children aged 0–12 months – 16.1 %, of which 65.9 % were not vaccinated against measles. The results of nucleotide sequencing of 69 samples from measles patients showed two genotypes – D8 and B3. Discussion: Measles cases in 2023 were registered throughout Kazakhstan. Measles virus genotype D8 was represented by the predominant line 8248, identified in Tajikistan in 2021 and circulating in Europe. Genotype B3 was associated with strains first identified in India and Saudi Arabia. These data confirm that measles incidence in Kazakhstan was attributed to viruses imported from other countries. Conclusion: Findings of epidemiological analysis and molecular genetic testing of measles viruses confirm continued circulation of genotypes B3 and D8 and emphasize the importance of continuing monitoring and increasing vaccination rates to control the disease spread.