Clark County reports first local clade I mpox case without clear travel link

Clark County case

The Southern Nevada Health District reported the case in a broader update on mpox activity in the Las Vegas area. The district described the infection as clade I. Clark County has logged 365 mpox cases since the virus was first detected locally in June 2022, and 11 confirmed clade II cases surfaced between August and October 2026.

The district said the resident had no reported travel exposure, leaving the source of transmission unclear. Health officer Dr. Cassius Lockett said mpox continues to circulate in the community and urged people at risk to get vaccinated and those potentially exposed to seek guidance promptly. He said recognizing symptoms early and avoiding close contact with others while sick can help prevent further spread.

National clade I count

The CDC's 25 September update, issued before the Clark County case was announced, reported more than 60 laboratory-confirmed clade I cases across at least 20 states. Since August, an increasing proportion of US clade I cases have occurred in people with no recent international travel or known links to recent travelers. Presumed domestic transmission has been reported in more than 10 jurisdictions, which the CDC said indicates a "likely transition to sustained Clade Ib transmission in the United States."

The agency still assesses the risk from the clade I outbreak as low for most people and says more travel-related and domestically acquired cases are expected. As recently as August, the CDC said sustained clade Ib transmission had not been detected in the United States.

The first known US clade I case was confirmed in a traveler returning from Eastern Africa to California in November 2024, according to the CDC. Long Beach, California recorded the first locally acquired US case in October 2025, in a patient with no travel history, CIDRAP reported.

Severity and vaccine

Johns Hopkins Bloomberg School of Public Health puts clade I case fatality rates at 1% to 10% in African outbreaks, against less than 1% to 4% for clade II. In the US, travel-associated clade I cases have been almost exclusively subclade Ib, with no deaths and mostly mild illness, the Oregon Health Authority said. The Oregon agency urged people at higher risk to get vaccinated as clade I transmission rose in western Europe and parts of Africa.

The Jynneos vaccine is expected to protect against both clade I and clade II, and the adult regimen is two doses 28 days apart, the CDC says. Post-exposure vaccination works best within four days of exposure, though shots given between four and 14 days afterward can still help. Clinics affiliated with the health district had administered more than 11,740 Jynneos doses by August 2024, after the 2022 clade II outbreak. The district continues to offer the vaccine at its immunization clinics and advises anyone potentially exposed to monitor for symptoms for 21 days after their last contact.