Detection of Community Transmission of Clade Ib Mpox Virus in the United States

Eric C Tang1, Monica Haw1, Sonali Kulkarni2

  • 1California Department of Public Health, Richmond, CA, USA.

NEJM Evidence
|December 17, 2025
PubMed

Insights

Local mpox virus (MPXV) transmission is occurring in the Americas. Three unvaccinated men in California were infected with clade Ib MPXV, with genetic links to a travel-associated case, indicating community spread.

Area of Science:

  • Epidemiology
  • Virology
  • Public Health

Background:

  • Clade Ib mpox virus (MPXV) outbreaks have been documented in Central and Eastern Africa, with travel-associated cases reported globally.
  • Recent mpox virus (MPXV) infections in unvaccinated individuals without international travel history raise concerns about local transmission.

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