Notes from the Field: Clade II Mpox Surveillance Update — United States, October 2023–April 2024

Two clades of monkeypox virus (MPXV) are known to cause human illness: clade I, which is endemic in Central Africa and is currently increasing in the Democratic Republic of the Congo, and clade II, which caused a global outbreak starting in 2022.Clade IIassociated disease is considered less severe than that of clade I and is typically self-limiting; however, immunocompromised persons, especially those with advanced HIV (i.e., CD4 T lymphocyte cell count <200 cells/mm 3 ), have experienced more severe infections (1,2).Clade II MPXV continues to circulate at low levels in the United States, but no cases of clade I MPXV have been reported.National mpox case counts peaked at approximately 3,000 per week during late July-August 2022 (Figure ), then sharply declined and remain substantially lower than case counts during the peak (59 cases per week during October 1, 2023 -April 30, 2024)).This report summarizes mpox surveillance data reported to CDC during October 1, 2023-April 30, 2024.This activity was reviewed by CDC, deemed not research, and was conducted consistent with federal law and CDC policy.*