Eric C. Tang, Monica Haw, Sonali Kulkarni, Emily K. Johnson, Crystal M. Gigante, Nora Balanji, Ricardo Berumen, Shama Cash‐Goldwasser, Jennifer Chevinsky, Alex Espinosa, Andrea Gallegos, Nicole M. Green, Jill K. Hacker, Faisal S. Minhaj, Erin Nguyen, Cliff Okada, Kathleen Poortinga, Will Probert, Kayla Saadeh, Aisling Vaughan, Shuang Wu, Debra A. Wadford, Kathleen M. Jacobson
AbstractA clade Ib mpox virus (MPXV) outbreak in Central and Eastern Africa has led to multiple travel-associated infections. In October 2025, clade Ib MPXV infection was confirmed in three unvaccinated, hospitalized men in California reporting no international travel. Phylogenetic analysis revealed clustering of these three MPXV infections with one recent travel-associated MPXV infection. This report provides evidence for local transmission of clade Ib MPXV in the Americas, occurring among gay, bisexual, and other men who have sex with men and their social networks.