Pandemiology Watch (December 24-30, 2025)
MEASLES
Mexico.
Mexico has reported 5,741 confirmed measles cases and 24 deaths as of 28 December 2025, according to national health authorities. The outbreak, which began in February 2025, has spread to 29 states and 207 municipalities. Chihuahua remains the epicentre, accounting for 77,8% of cases and 87,5% of deaths. Most cases are among unvaccinated individuals, particularly children aged 0–4 years. Ongoing transmission threatens Mexico’s measles elimination status maintained since 2016.
US.
No new measles updates were published by the Center for Disease Control and prevention during the period 24–30 December 2025. The most recent CDC data available prior to this period, reported on 23 December 2025, indicate a total of 2,012 confirmed measles cases in the United States in 2025. Of these, 227 cases (11%) required hospitalization, and three deaths were reported.
Canada.
As of December 30, 2025, Canada has reported 5,377 measles cases where 71% occurred in children, according to the Public Health Agency of Canada. Ontario accounts for 45% 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
According to the UK Government’s Outbreaks under monitoring report for week 52 (week ending 28 December 2025), a total of 14 confirmed cases of Marburg virus disease, including 9 deaths, have been reported in Ethiopia since the outbreak was confirmed in mid-November 2025.
Rift Valley Fever
Senegal.
On December 24, Africa CDC reported a total of 554 confirmed Rift Valley Fever cases in Senegal, including 11 new cases since the update on December 17. In addition, 19,159 suspected cases have been reported in total.
MPOX
There have been no new mpox updates reported during the period 24–30 December 2025. 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 December 30, 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
No new update has been published during the period 24–30 December 2025 since the Polio This Week report dated 17 December 2025. The Global Polio Eradication Initiative recorded new poliovirus detections in several countries. In Africa, detections included one cVDPV2 case and two cVDPV3 cases in Chad, one cVDPV2 case in Ethiopia, five cVDPV2 cases in Sudan, one cVDPV2-positive environmental sample in Somalia, and two cVDPV2-positive environmental samples in Tanzania. Outside Africa, Pakistan recorded 38 WPV1-positive environmental samples, and Yemen reported four cVDPV2-positive environmental samples.