Investigating Local Patterns of Mumps Virus Circulation, Using a Combination of Molecular Tools.

Area of Science:

• Virology
• Epidemiology
• Molecular Biology

Background:

• Mumps virus (MuV) remains a public health concern due to re-emergence in highly vaccinated populations.
• The World Health Organization recommends molecular surveillance using the small hydrophobic (SH) gene for mumps.
• Combined sequencing of SH and non-coding regions (NCR) has shown utility in tracking national and international MuV circulation patterns.

Purpose of the Study:

• To evaluate the utility of combining SH and MF-NCR sequencing for identifying local mumps transmission clusters and chains.
• To analyze the last epidemic wave (2015-2020) of mumps in the Autonomous Community of Madrid, Spain.

Main Methods:

• Generated a database of 903 mumps cases, integrating microbiological and epidemiological data.
• Genotyped 453 representative cases, focusing on SH gene sequencing.
• Phylogenetically analyzed 90 cases using combined SH and MF-NCR sequencing to investigate transmission clusters.

Main Results:

• Detected eight distinct SH variants and thirty-four SH haplotypes among the genotyped mumps cases.
• Observed temporal circulation patterns consistent with national-level data.
• Identified previously undetected local transmission clusters using geographical representation of SH variants.
• MF-NCR sequencing did not significantly improve the discrimination of geographical clusters compared to SH sequencing alone, indicating limited resolution for detailed outbreak investigations.

Conclusions:

• SH gene sequencing, complemented by MF-NCR analysis, is valuable for identifying local mumps transmission clusters.
• The combination of SH and MF-NCR sequencing demonstrated limited added value for fine-scale outbreak investigations in this study.
• Molecular surveillance strategies should consider the resolution limitations of different genetic markers for effective public health interventions against mumps.