Pandemiology Watch (October 29-November 4, 2025)
H5N1
A new scoping review published online in JAMA Network Open on October 29, 2025, found that 18 cases of human infection with the H5N1 avian influenza virus were reported as asymptomatic in the published literature. Of these, 2 had both molecular and serologic confirmation, and 16 had molecular confirmation alone, suggesting that unnoticed infections can occur in people exposed to the virus.
U.S.
On November 4, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service updated its data on H5N1 highly pathogenic avian influenza detections in mammals. The virus has been confirmed in species such as red foxes, raccoons, skunks, bears, and seals, indicating continued spillover from infected wild birds.
As of November 4, Centers for Disease Control and Prevention has not reported any cases of person-to-person transmission of H5N1 in the United States. The total remains at 70 confirmed human cases and one death.
MEASLES
U.S.
Measles cases are rising in the U.S. according to CIDRAP on November 3, 2025. In Utah, there are now 64 confirmed cases, with 61 among unvaccinated individuals and 49 linked to the Southwest Utah Health zone. The Utah?Arizona outbreak has reached 142 cases, making it the second largest in the country this year, after the West Texas outbreak.
On October 29, 2025, Salt Lake County Health Department reported a probable first measles case in the county this year. The patient declined testing and did not fully participate in the investigation, which prevented completion of contact tracing. However, based on the symptoms reported by the healthcare provider, the case is considered very likely to be measles.
As of October 30, 2025, Center for Disease Control reports a total of 1,648 confirmed measles cases in the U.S. in 2025. 12 % of cases have required hospitalization (202 cases of 1,648), and three deaths have been reported.
Canada.
As of November 3, 2025, Canada has reported 5,138 measles cases where 71% occurred in children, according to the Public Health Agency of Canada. Ontario accounts for 47% of the cases, followed by Alberta with 38%. 88% were unvaccinated, and 7% required hospitalization. Genotype D8 remains the most frequently detected strain. 2 deaths have been reported.
Rift Valley Fever
Senegal.
Between October 29 and November 3, 2025, the weekly Africa CDC update for Rift Valley Fever in Senegal did not list any new cases. The most recent data, from October 27, showed 1,989 suspected cases, 277 confirmed cases, and 22 deaths. Of the reported cases, 64% were male, 56% were aged 15–34, and 87% occurred in the Saint Louis region.
Mauritania.
From October 29 to November 3, 2025, the weekly Africa CDC update for Rift Valley Fever in Mauritania did not report any new cases. The most recent available figures remain from October 27, when Africa CDC reported 133 suspected cases, 43 confirmed cases, and 14 deaths. Males accounted for 79% of cases, and 81% of cases were in individuals over 10 years old.
MPOX
Africa.
Sierra Leone: The latest update from the World Health Organization shows 5,442 confirmed mpox cases as of October 26, a surge of 9 cases since October 19. For the week of October 29 to November 3, 2025, no new Africa CDC update was issued; the latest report from October 27 linked the outbreak to clade 2b and noted that 6.5% of cases were in children under 15 years, 52% were male, and the positivity rate was 77%.
Uganda: As of October 26, 2025, Uganda reported 6,970 confirmed mpox cases, according to the World Health Organization. This is an increase of 74 cases since October 12.
Guinea: As of October 12, 2025, The World Health Organization has reported 1,077 cases in 2025 and one death in Guinea. This is an increase of 20 cases since October 12. According to Africa CDC testing shows a 42% positivity rate, and the outbreak is linked to clade 2b.
POLIO
As of October 29, 2025, the Global Polio Eradication Initiative reported new poliovirus detections. Pakistan reported one WPV1 case and twelve WPV1-positive environmental samples. Papua New Guinea reported one cVDPV2 case and five positive environmental samples.
In Africa, Angola reported two cVDPV2 cases and one positive environmental sample, Chad reported one positive environmental sample, Nigeria reported seven cVDPV2 cases and one positive environmental sample, and Somalia reported one positive environmental sample.