MONDAY, Aug. 24, 2026 (HealthDay News) -- Fewer cases of mpox virus (MPXV) infection were reported in 2025 than 2024, but the number of reported cases during September to October 2025 was double that seen in 2024, according to research published in the Aug. 20 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.Ryan Sandford, M.P.H., from the CDC in Atlanta, and colleagues examined trends in cases of MPXV infection in the United States during 2024 to 2025 using data from the One CDC Data Platform and the National Notifiable Diseases Surveillance System.Overall, 2,803 cases were reported in the United States in 2024, including one travel-associated clade Ib case. The researchers identified 2,519 cases that were reported in 2025, including 10 clade Ib cases. During September to October 2025, the number of reported cases of MPXV infection was double that seen during the same period in 2024; by the end of December 2025, cases returned to background levels. Demographic characteristics of patients with MPXV infections were similar to those reported in previous years, including distributions by sex, race and ethnicity, sexual orientation, lesion location, and age. Among 860 patients with complete information, when controlling for age group and HIV status, the odds of hospitalization were 9.73 times higher for those who were unvaccinated versus those who were fully vaccinated."The changing epidemiology of MPXV infections globally, including new viral lineages and travel-associated cases, a doubling of cases during fall 2025 compared with fall 2024, and the higher odds of hospitalization among unvaccinated patients, all suggest that more work is needed to prevent MPXV transmission in the United States," the authors write.Abstract/Full Text.Sign up for our weekly HealthDay newsletter