Molecular epidemiological surveillance of respiratory syncytial virus infection in Myanmar from 2019 to 2023

Abstract

To evaluate genetic changes in respiratory syncytial virus (RSV) between 2019 and 2023, we analyzed RSV strains from Myanmar before and after the COVID- 19 pandemic. Real-time polymerase chain reaction (RT-PCR) positive samples from children presenting with acute respiratory infections at outpatient clinics in Yangon were sequenced to determine the genotype. Phylogenetic and molecular evolutionary analyses were conducted using the Bayesian Markov Chain Monte Carlo method to construct the time-scale Maximum Clade Credibility tree. Of 1127 samples, 104 (9.2%) RSV-A and 233 (20.7%) RSV-B were positive by RT-PCR. There was an absence of a notable epidemic in 2020, a temporal shift with a surge of RSV-A in the 2021 outbreak, a lack of expected cases in 2022 and a substantial resurgence of RSV-B in 2023. The genotype of RSV-A was mainly A.D.3 lineage through the study period, while RSV-B were B.D.4.1.1 and B.D.E.1. RSV-A showed that the same lineage persisted within Myanmar throughout the pandemic, leading to a large outbreak post-COVID. In contrast, RSV-B strains appear to have temporarily disappeared during the pandemic, but subsequently, globally circulating strains likely entered Myanmar, resulting in a major outbreak in 2023. The estimated evolutionary rate at the G-ectodomain for RSV-A was 7.76 × 10⁻³ and RSV-B was 5.67 × 10⁻³ substitutions/site/year. Strengthening genomic surveillance will likely support comparisons of circulating strains with those in other countries and facilitate the introduction of vaccines and other interventions.

Keywords: COVID- 19 pandemic; Evolutionary rate; G gene; Molecular epidemiology; Respiratory syncytial virus.

Fig. 1

Geographic map of Yangon, Myanmar, showing the locations of Yankin Children’s Hospital and Thingangyun General Hospital (red crosses) where samples were collected. This study used Myanmar digital administrative boundaries map from Myanmar Information and Management Unit (MIMU), Myanmar (https://www.themimu.info/search/external? field_search=Myanmar% 20State% 20and% 20Region% 20Boundaries% 20MIMU% 20v9.4 (accessed on 25 February 2025). Yankin Children’s Hospital (N16.7883˚ E96.1364˚) and Thingangyun General Hospital (N16.8327˚, E96.192˚) are located in Yankin and Thingangyun areas in Yangon, Myanmar, respectively.

Fig. 2

The monthly distribution epidemic curve of respiratory syncytial virus (RSV) collected in Myanmar from 2019 to 2023. The gray shading represents the number of nasal swab samples collected; the orange bar graph represents the number of RSV-A-positive samples (n = 104) detected using real-time polymerase chain reaction (RT-PCR); the blue bar graph represents the number of RSV-B-positive samples (n = 233) detected using RT-PCR; the gray line represents the number of cases that tested positive using a rapid diagnostic test (RDT).

Fig. 3

Time-calibrated maximum clade credibility (MCC) tree inferred from RSV-A G-ectodomain sequences in Myanmar and reference sequences from other countries. The branches are on a time scale in years and are color-coded according to the location of the most probable ancestor of descendant nodes. Genetic lineages and unique amino acid substitutions are pointed out using black arrows.

Fig. 4

Time-calibrated MCC tree inferred from RSV-B G-ectodomain sequences in Myanmar and reference sequences from other countries. The branches are on a time scale in years and are color-coded according to the location of the most probable ancestor of descendant nodes. Genetic clade and unique amino acid substitutions are pointed out using black arrows.