Studies Document Brain Swelling, Sepsis in U.S. Measles Outbreaks

As U.S. measles cases approach last year’s record-breaking total, studies on South Carolina and Utah’s large outbreaks showed cases of encephalitis and sepsis among the hospitalized patients.

In both states, hypoxemia and pneumonia were the most common conditions leading to hospitalization for measles, with some admissions driven by electrolyte abnormalities, sepsis, and shock.

Two of 13 patients hospitalized in South Carolina developed measles encephalitis, which led to prolonged hospitalization for both and discharge to an inpatient rehabilitation facility for one patient, according to Katherine Richardson, MD, and colleagues from Prisma Health Greenville Memorial Hospital in South Carolina, writing in the New England Journal of Medicine.

In Utah, 54% of the hospitalized measles patients with lab results had hyponatremia or lymphopenia, 37% had thrombocytopenia, and 30% had elevated alanine aminotransferase. More than half of those with chest radiographs showed abnormalities (55%), and most patients received intravenous fluids (78%) or supplemental oxygen (61%), reported Anna Jones, MD, of the Utah Department of Health and Human Services in Salt Lake City, and co-authors in NEJM Evidence.

Historically, about 20% of unvaccinated people who get measles are hospitalized. In contrast, the current Utah outbreak has seen a hospitalization rate of about 8% among the 602 patients in the Jones and colleagues report, in line with the rate seen during New York’s 2018-2019 outbreak. Among the 81 South Carolina patients, 16% ended up in the hospital.

“Measles is back, and measles is back because we have a critical percentage of parents who are choosing not to vaccinate their children,” Paul Offit, MD, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, told MedPage Today. “There’s just no good reason to not get a vaccine.”

Widespread vaccination led to measles’ eradication in the U.S. by 2000, but the highly contagious virus has surged in recent years as vaccine skepticism spreads among some groups and communities.

The U.S. has seen 32 new outbreaks and 2,238 confirmed measles cases as of July 9, 2026, according to the CDC. That pace will almost certainly race past 2025’s entire tally of 2,289 cases. Among confirmed measles cases, 93% of people in 2025 and 2026 were unvaccinated or had unknown vaccination status.

Three-quarters of the measles-positive patients that South Carolina’s Prisma Health system identified during the state’s measles outbreak from October 2025 to April 2026 were 18 years or younger. Among the 81 patients, 72.8% were unvaccinated and 3.7% had an unknown vaccination status.

Utah’s ongoing measles outbreak has mirrored those trends. Among 602 measles cases from June 2025 to April 2026, 85% weren’t vaccinated and 5% had an unknown vaccination status. Of the 49 people hospitalized with measles, 90% were unvaccinated and 59.2% were under 18 years.

Among the Utah hospital cases, the median number of symptomatic days before admission was 5, and the mean length of stay was 2.1 nights. Nine of the 13 patients admitted in South Carolina were hospitalized for less than 72 hours.

The most common symptoms among the 81 measles-positive people in South Carolina were fever (96%), rash (85%), cough or other respiratory symptoms (71%), nasal symptoms (55%), and eye symptoms (32%). Koplik spots showed up more often than expected (26%), given that the symptom usually resolves by the time patients present with fever and rash.

Of the South Carolina patients, 24 had concurrent or subsequent infections within a month after their diagnoses. Otitis media, pneumonia, and sinusitis were the most common infections.

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