Arizona confirms first case of deadlier mpox strain

Key Points:

• Arizona has confirmed its first case of the more lethal Clade I strain of mpox, contracted by a patient who traveled outside the U.S., though there is no evidence of local spread in the state.
• Clade I mpox is more severe and has higher death rates compared to the more common Clade II strain, which has been circulating in the U.S. since 2022; as of June 2026, at least 20 Clade I cases have been reported nationwide.
• Mpox spreads primarily through skin-to-skin contact with sores or body fluids and less commonly through contaminated items or prolonged close contact; casual contact in public places is unlikely to transmit the virus.
• The Arizona Department of Health Services is withholding patient details for privacy and emphasizes that both Clade I and II cause similar symptoms and require the same prevention measures, including vaccination and clinical management.
• Vaccination with the JYNNEOS vaccine is recommended for those exposed to mpox, ideally within four days of exposure, to prevent infection or reduce severity, and infected individuals should isolate until all lesions have fully healed.