Pandemiology Watch (December 31, 2025-January 6, 2026)
Emerging outbreaks
On 5 January 2026, the Wisconsin Department of Natural Resources confirmed the first case of chronic wasting disease in a wild deer in Clark County. The infected deer was taken by a hunter, and the county’s baiting and feeding ban was extended for three years.
MEASLES
US.
On January 5, 2026, CIDRAP reported that measles cases in South Carolina had risen to 188, primarily linked to an outbreak in the Upstate region. In Arizona, the outbreak has reached 205 cases, and 156 cases have been reported in Utah. Most cases involve unvaccinated individuals, with transmission mainly in schools and households.
As of December 31, 2025, Center for Disease Control reports a total of 2,065 confirmed measles cases in the U.S. in 2025. 11 % of cases have required hospitalization (235 cases of 2,065), and three deaths have been reported.
Canada.
As of January 5, 2026, Canada has reported 5,393 measles cases where 71% occurred in children, according to the Public Health Agency of Canada. Ontario accounts for 44% of the cases, followed by Alberta with 37%. 89% were unvaccinated, and 7% required hospitalization. Genotype D8 remains the most frequently detected strain. 2 deaths have been reported.
Marburg virus
For the period 31 December 2025 to 6 January 2026, no new updates on Marburg virus disease were reported. In the most recent update, published in the UK Government’s Outbreaks under monitoring report for week 52, 14 confirmed cases, including 9 deaths, had been reported in Ethiopia since the outbreak was confirmed in mid-November 2025.
Rift Valley Fever
Senegal.
No new updates on Rift Valley Fever have been reported in Senegal during the period 31 December 2025 to 6 January 2026. In Africa CDC’s latest update on 24 December 2025, a total of 554 confirmed Rift Valley Fever cases were reported, including 11 new cases since 17 December, along with 19,159 suspected cases.
MPOX
There have been no new mpox updates reported during the period December 31 2025-January 6 2026. In recent weeks, reports from Europe and the United States have documented the spread of mpox clade Ib outside Africa, including local and community transmission without travel history. Evidence from Ireland, Spain, the U.S. and the UK highlights onward transmission and evidence of ongoing viral chance. These developments underline the continued need for surveillance and public health preparedness.
H5N1
U.S.
As of January 6, the Centers for Disease Control and Prevention reports has not reported any cases of person-to-person transmission of H5N1 in the United States. The total remains at 71 confirmed human cases and two deaths.
POLIO
As of December 31, 2025, the Global Polio Eradication Initiative reported new poliovirus detections in Somalia. These include one cVDPV2 case and one cVDPV2-positive environmental sample.