Pandemiology Watch (March 25-31, 2026).
Emerging outbreaks
Pertussis
According to CIDRAP on March 26, 2026, pertussis cases in the Americas declined slightly in 2025 to 46,870 cases, down from 66,184 in 2024 after a post-pandemic increase. The United States reported the most cases, with 28,783 cases and 16 deaths in 2025, and 2,355 cases and one death have been reported so far in 2026. Adolescents and young children were the most affected age groups, and booster vaccination remains important to maintain immunity.
Meningitis
According to the UK Health Security Agency (UKHSA), 21 confirmed cases of invasive meningococcal disease linked to Canterbury, Kent had been reported as of March 31, 2026, including 2 deaths. All confirmed cases were meningococcal group B (MenB), and 18 were linked to the outbreak strain subtype P1.12-1,16-183. The UKHSA said that the strain is not a new meningococcal type and has been present in England since 2020, but the outbreak genome appears distinct with multiple genetic differences that are still being evaluated. Most cases involved young adults, many of them students, linked to University of Kent and Club Chemistry in Canterbury. Vaccination history was unknown for the cases reviewed, and the response has included antibiotics and MenB vaccination for at-risk groups.
MEASLES
US
According to CIDRAP on March 27, 2026, several US states reported new measles cases. Texas reported 23 new cases, bringing the total to 170 cases this year, with many cases linked to a detention center in Hudspeth County. Arizona reported two new cases, bringing the total to 60 cases, while Florida has reported 128 cases so far this year. Idaho reported one new case, bringing the total to 23 cases, and North Dakota remains at 26 cases. South Carolina reported no new cases and the outbreak total remains at 997 cases.
As of March 27, 2026, the United States has reported 1,575 measles cases so far in 2026, according to the Center for Disease Control. In 2026, the age group 5-19 accounts for 52% of the cases (814), and children under 5 years account for 21% of the cases (330). Of the cases reported in 2026, 92% were unvaccinated or had an unknown vaccination status and 5% of the cases have been hospitalized (78). A total of 3,860 measles cases and three deaths have been reported to date.
Canada
As of March 30, 2026, Canada has reported 650 measles cases in 2026, according to the Public Health Agency of Canada. In 2026, 60% of the cases occurred in children (392). Manitoba accounts for 60% of the cases (392), and Alberta accounts for 32% of the cases (209) reported so far in 2026. 89% of the cases reported in 2026 were unvaccinated (581), and 7% required hospitalization. A total of 6,075 measles cases and two deaths have been reported to date.
Influenza
According to the Centers for Disease Control and Prevention on March 27, 2026, 123 pediatric influenza deaths have been reported in the United States during the 2025-2026 flu season. In the latest weekly influenza surveillance report, eight additional child deaths linked to influenza were reported. Most of the children who died were not fully vaccinated against influenza.
H9N2
According to the European Centre for Disease Prevention and Control on March 25, 2026, Italy reported the first human case of avian influenza A(H9N2) in the EU/EEA in a traveller returning from a non-European country. The patient was hospitalised and isolated, and contact tracing was conducted. ECDC assessed the risk to the general population as very low.
H5N1
As of March 31, 2026, the 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 71 confirmed human cases and two deaths.
MPOX
From March 26-31, 2026, there have been no significant updates on mpox outbreaks worldwide.