Clade II Mpox Infections Among Cruise Ship Passengers and Crew Members — United States, 2024

PMCID: PMC12176104

PMID: 40531694

DOI: 10.15585/mmwr.mm7422a1

Journal: MMWR. Morbidity and mortality weekly report

Publication Date: 2025-6-19

Authors: Ortiz N, Rodriguez LR, McPherson M, Pringle K, Rao AK, et al.

Key Points

• Eight mpox cases identified across four cruise ship voyages, with transmission primarily among crew members and passengers on cruises targeting gay and bisexual men
• 3/4 passenger patients and 0/4 crew members had received prior JYNNEOS vaccination, indicating potential vaccine breakthrough
• Recommended strategies include pre-travel vaccination, onboard prevention education, and rapid public health interventions to mitigate transmission risks

Summary

This CDC investigation documented eight mpox infections among cruise ship travelers between January and April 2024, highlighting potential transmission risks in cruise ship environments. The cases involved four crew members and four passengers, predominantly on cruises marketed to gay and bisexual men, with seven laboratory-confirmed as clade II Monkeypox virus. Despite most patients having received prior JYNNEOS vaccination in 2022, they still contracted mpox, underscoring the virus's potential for breakthrough infections.

The study revealed critical insights into mpox transmission dynamics, including a three-person crew member cluster with 16 additional contacts. Notably, prompt interventions like patient isolation, contact tracing, and post-exposure prophylaxis (PEP) vaccination appeared effective in preventing secondary transmission. No hospitalizations or deaths occurred, and most patients presented with rash and fever, suggesting relatively mild disease manifestations.