A measles outbreak swept through central Ohio at the end of 2022, infecting almost exclusively children unvaccinated against the disease, CDC researchers found.
From November through December, 85 children across seven counties were infected, 94% of whom had not received the measles shot, reported Elizabeth C. Tiller, MSPA, an epidemiologist with the CDC's Epidemic Intelligence Service and with Columbus Public Health in Ohio, and colleagues.
The outbreak occurred during a peak coincident outbreak of COVID-19 and respiratory syncytial virus (RSV), leading to high rates of coinfection with other respiratory pathogens and twice the hospitalization rate reported in prior U.S. measles outbreaks, Tiller and coauthors wrote in .
According to Ohio school and public health records, 88.3% of kindergartners who entered school in the state in 2021-2022 were current with the two-dose measles, mumps, and rubella (MMR) vaccination schedule, which is about 5% below the national estimate of 93% coverage.
The Advisory Committee on Immunization Practices recommends two routine MMR vaccine doses for children, with the first dose administered at 12-15 months old and the second dose at age 4-6 years old, before school entry.
"This outbreak serves as a reminder that health care facilities, medical providers, and child care facilities serving undervaccinated populations should maintain vigilance for measles and emphasize the importance of timely MMR vaccination," the authors said. "Sustaining elimination of measles in the United States will require continued high 2-dose MMR vaccination coverage in all communities."
All 85 cases were locally acquired, the team said. However, they did note that four internationally acquired measles cases occurred in the same area from June through October 2022 among unvaccinated adults who had traveled to an area of East Africa with an active outbreak.
While all of the genotyped cases were of the same lineage (B3), the authors could not link them directly to the imported cases, nor did they identify the genotype of the imported cases.
"Although measles was declared eliminated in the United States in 2000, it remains endemic in many countries, and internationally imported cases continue to be associated with outbreaks among undervaccinated, close-knit communities in the United States," the team wrote.
The four imported cases occurred from June 12 through Oct. 8, 2022, in Franklin County, Ohio, which also had the largest number (78) of subsequent local cases. Two cases occurred in adjacent Madison County and one each in Clark, Fairfield, Richland, Ross, and Union counties, all in central Ohio. The outbreak was declared over on Feb. 4, 2023 -- 42 days after the last reported case.
The first patients were two 2-year-olds admitted to a local hospital on Nov. 5, 2022, with rash, fever, cough, and congestion. While the symptoms were suggestive of measles, it was not initially considered in the differential diagnoses, despite neither child having received a dose of the MMR vaccine. Neither child had traveled internationally or been in contact with a known active measles case, but both were positive for measles by real-time reverse transcription–polymerase chain reaction (RT-PCR).
After the positive tests, local authorities identified additional cases and confirmed a community outbreak on November 9.
They confirmed 85 cases in seven counties with confirmed rash onset from Oct. 22 to Dec. 24, 2022. The Ohio Department of Health Public Health Laboratory performed RT-PCR testing on specimens from 193 persons during the outbreak, confirming 74 (87%) of the cases. The remaining 11 (13%) were epidemiologically linked to confirmed cases.
The median patient age was 1 year (range 6 months to 15 years). While 71% of the cases (60 patients) had reached at least a year old and thus were eligible for the MMR vaccine, only three of those children had received it. Overall, 80 patients (94%) were unvaccinated. One patient's vaccination status was undetermined.
Complications were common among the group, with 44 patients (52%) experiencing at least one. These included otitis media in 39%, diarrhea in 26%, and pneumonia in 8%.
Hospitalization was necessary for 36 (42%), most of whom were admitted with dehydration. The median length of stay was 3 days, although that ranged up to 7 days. Coinfections with RSV occurred in 12 hospitalized patients. There were no deaths.
Exposures most commonly occurred in community settings, including five healthcare facilities (38%) and four childcare facilities (26%). Household exposures accounted for 20%.
The public health departments of the city of Columbus and of Franklin County identified 739 local contacts who were either unvaccinated or had unknown vaccination status. These individuals were quarantined, with 446 (60%) actively monitored. Among these, 43 (10%) developed measles, with two-thirds being quarantined before the onset of rash.
Among the contacts, 59 received postexposure prophylaxis, with immune globulin for most (88%) and MMR vaccination in eight cases (14%). Two children who received the MMR vaccine later developed measles, although there were no cases among the children who received immune globulin.
Ohio's last prior measles outbreak occurred in 2014.
Disclosures
Tiller had no disclosures. Coauthors reported relationships with the Big Cities Health Coalition, the Council of State and Territorial Epidemiologists for the Influenza Population-based Hospitalization Surveillance Project, and the COVID-19–associated Surveillance in Children and Adults Project.
Primary Source
Morbidity and Mortality Weekly Report
Tiller EC, et al "Notes from the Field: Measles outbreak -- Central Ohio, 2022-2023" MMWR 2023; DOI: 10.15585/mmwr.mm7231a3.