# Prevalence and Molecular Profiling of Merkel Cell Polyomavirus in Patients With Monkeypox Virus Infection

## TL;DR

This study finds that Merkel Cell Polyomavirus is commonly present in people infected with Monkeypox virus, particularly in anal swabs, and suggests it may persist during recovery.

## Contribution

The study is the first to detect Merkel Cell Polyomavirus in Monkeypox patients and explores its molecular characteristics during acute infection and follow-up.

## Key findings

- Merkel Cell Polyomavirus DNA was detected in 34.8% of Monkeypox patients, with higher prevalence in anal swabs.
- Merkel Cell Polyomavirus persisted in some patients at 9-month follow-up and showed active gene expression.
- Among HIV-positive individuals, MCPyV load varied between oropharyngeal and anal swabs compared to non-HIV cases.

## Abstract

Mpox, caused by Monkeypox virus (MPXV), is associated with mucosal involvement and immune modulation that may influence viral coinfections. Merkel Cell Polyomavirus (MCPyV), a ubiquitous virus capable of lifelong persistence, was investigated in 66 Mpox patients enrolled at Lazzaro Spallanzani National Institute for Infectious Diseases (Rome, Italy; 2022–2025). Oropharyngeal and anal swabs collected during acute Mpox and, at 9‐month follow‐up, were analyzed by quantitative PCR, sequencing, transcript, and microRNA assays. MCPyV DNA was detected in 23/66 (34.8%) individuals, with higher prevalence and load in anal (31.8%, 2.1 × 103 copies/mL) than in oropharyngeal swabs (24.4%, 1.3 × 102 copies/mL; p < 0.001). MCPyV persisted in 4/10 (40%) oropharyngeal samples at follow‐up. No viral integration was observed, and full‐length Large Tumor Antigen was amplified in all samples. Transcript analysis revealed early and late genes; viral microRNAs were found in 3/10 (30%) oropharyngeal and 5/14 (35.7%) anal acute‐phase swabs, and persisted in 3/4 (75%) MCPyV‐positive oropharyngeal samples at follow‐up. Among the 12 MCPyV‐positive people living with human immunodeficiency virus (HIV), MCPyV load was lower in oropharyngeal but higher in anal swabs compared to MCPyV/MPXV cases. This study provides the first evidence of MCPyV detection in Mpox‐positive individuals and supports further investigation of its clinical relevance in coinfection settings.