2023 Highlights
- Minnesota reported 70 cases, the highest annual total since 2017; including one large outbreak in the 7-county Twin Cities metropolitan area (52 cases) and 18 additional travel-related cases.
- Measles was reported across multiple U.S. states, with an increase in both isolated clusters and sustained outbreaks.
In 2024, 70 measles cases were reported in Minnesota. Forty-nine cases (49) were residents of Hennepin County, and the remaining were residents of Ramsey (8), Dakota (4) and Anoka (9) counties. Of the 70 cases, 63 (90%) were laboratory confirmed, and 7 (10%) were epidemiologically linked to laboratory confirmed cases. All 63 lab confirmed cases were positive by PCR and genotyping was performed; 45 (71%) were genotyped as D8, 17 (27%) were genotyped as B3, and one (2%) failed to be successfully genotyped.
Measles transmission in 2024 occurred most often in household (n=28) and travel-related (n=13) settings, which together accounted for more than half of all identified transmission events. Additional exposures took place in extended family or friend gatherings (12), community settings (8), childcare facilities (5), health care settings (3), and schools (1). The median age of cases was four years (range: 7 months–54 years). Most cases (63; 90%) were among Black individuals; 6 (9%) white, non-Hispanic individuals; and one (1%) Hispanic individual of unknown race.
Of the 70 cases, 68 (97%) were unvaccinated, of those 68, 6 (9%) were too young for vaccine and 62 (91%) were of age but unvaccinated. In addition, two (3%) adults reported a history of vaccine, although no documented doses could be located. Twenty-three (33%) cases were hospitalized (mean 3.91 days; range 2-7 days).
Fifty-two (74%) of the 70 cases reported were associated with an outbreak that began within the northern seven-county metro area. The first cases in the outbreak were identified in May in one family with recent international travel. Measles was reported among several members of an extended family who were hesitant to engage in public health interviews or follow-up interventions, limiting the ability for public health staff to assess the extent of transmission. Ongoing transmission occurred but was not captured in surveillance due to limited communication with public health staff after the initial confirmed cases.
The outbreak continued in late July, when three measles cases were reported (rash onset July 18 and 23). These cases had no travel, no known exposures, and no links to one another; however, genotyping matched the May-June cases, and the timing was compatible with exposure during that period, despite occurring in a different cultural community and without a confirmed epidemiologic link. The outbreak was declared over in November and mainly affected unvaccinated children in a highly susceptible MN community.
In addition to the 52 outbreak-associated cases, there were 18 non-outbreak cases reported between February and November. These represented separate, unrelated cases occurring both before and after the outbreak. The majority of these cases had traveled or were exposed to a case who had traveled.
Although measles was declared eliminated in the U.S. in 2000, cases and outbreaks are rising again due to increasing global circulation, declining vaccination (MMR) coverage, and growing distrust in public health. In Minnesota, MMR rates among two-year-olds have fallen five percentage points since 2019, with some children still not caught up after pandemic disruptions. Communities with low coverage are especially vulnerable, and the mix of rising importations and local immunity gaps heightens the risk of an outbreak. Vaccination remains critical to protecting at-risk Minnesotans.
