Molecular characterization and genetic diversity of mumps virus genotype G in Pakistan during the 2023 outbreaks

Mumps, despite being a vaccine-preventable disease, poses a significant public health challenge globally. In Pakistan, the absence of mumps vaccination in the national immunization program, coupled with limited epidemiological and surveillance data, presents a concerning scenario. This study investigates the molecular epidemiology of the Mumps virus (MuV) during the 2023 outbreaks, focusing on the genetic variability of the small hydrophobic (SH) gene, a key determinant for viral evolution and genotyping. Buccal swabs were collected from suspected patients presenting swollen parotid glands during the outbreak periods. Out of 62 mumps suspects, 40 (64.5 %) samples tested positive for MuV through RT-PCR. The incidence rate of positive cases was higher in males (70 %) than in females (30 %), with the highest incidence observed in early childhood (0-5 year-old) infants. Phylogenetic analysis revealed that all the specimens belonged to genotype G, with 97.4 % homology with genotype G of MuV isolates from Spain and up to 98.73 % with Japan, and UK. This research study underscores Pakistan's vulnerability to mumps outbreaks due to the absence of mumps vaccine in the national immunization program and highlights the need for effective surveillance systems for Mumps in the country.