# An atypical case of infection with the Mpox virus clade IIb lineage C.1 – clinical and virological findings

## TL;DR

This paper reports an unusual mpox virus infection case in a Polish patient, highlighting the clinical and genetic features of the C.1 lineage of Clade IIb.

## Contribution

The study provides insights into the atypical clinical presentation of MPXV C.1 lineage in non-endemic regions.

## Key findings

- The patient showed localized lesions with minimal systemic symptoms.
- Genomic analysis confirmed infection with the MPXV C.1 lineage of Clade IIb.
- C.1 lineage infections may present atypically, especially in immunocompetent individuals.

## Abstract

We describe an atypical case of mpox virus (MPXV) infection in a Polish patient, with a focus on clinical presentation, virological characterisation, and the phylogenetic placement of the viral isolate within the emerging C.1 lineage of Clade IIb. The report aims to contribute to a better understanding of MPXV lineage-specific disease features and viral evolution in non-endemic settings. The patient presented with numerous localised lesions and minimal systemic symptoms. Genomic analysis confirmed infection with an MPXV C.1 lineage of Clade IIb responsible for the 2022–2025 global outbreaks. Infection with C.1 lineage may lead to atypical presentations, particularly in immunocompetent individuals. Continued genomic surveillance and clade-specific clinical correlation are essential for accurate diagnosis, risk stratification, and public health response.