Public health experts link the surge in cases to a decline in routine immunization. According to ColombiaOne, the percentage of U.S. kindergarteners who are vaccinated dropped from 95.2 percent in the 2019-2020 school year to 92.4 percent during the 2025-2026 school year. This decline has contributed to a situation where the virus is spreading through undervaccinated communities. In the 2025-26 school year, vaccine exemptions for personal beliefs and medical reasons exceeded 5 percent in 24 states.
Declining vaccination rates fuel outbreaks
Children and teenagers account for approximately 59 percent of confirmed cases, according to data from the CDC. Within this demographic, those between ages five and 19 represent 41 percent of the total, while children below the age of five make up 18 percent.
Dr. Andrew Handel, a pediatric infectious diseases physician at Stony Brook Children’s Hospital in Stony Brook, New York, noted how easily the disease spreads. It is the most contagious infection that we know of,
Handel said. the estimate is that for every person who has measles, they can infect up to 18 people who are unvaccinated with it.
The United States has recorded more than 5,000 cases of measles this year, the highest number in 35 years, according to an official count released Friday.
The CDC states that approximately 9 in 10 unvaccinated people who are exposed to the virus will become infected. The disease is characterized by a high fever, which can exceed 104 degrees Fahrenheit, and a rash that typically begins at the hairline and moves down the body. Other symptoms include a cough, runny nose, conjunctivitis, and Koplik spots, which are whitish or bluish dots found on the inside of the cheek.
Eight deaths reported across multiple states
Eight measles-associated deaths have been reported so far in 2026. State health officials confirmed six deaths in Pennsylvania, one in New York, and one in Wisconsin. In New York, the death of a child in upstate New York was the state’s first measles-related death in more than 30 years. In Wisconsin, health officials confirmed an infant died with the virus, marking the first such death in the state since 1990.
Discrepancies exist regarding the official death toll. While state officials have reported eight deaths, the CDC has confirmed four deaths and stated the number is subject to change.
This gap stems from a dispute over how deaths are classified.
Al Jazeera reported that the federal count became a point of contention between Pennsylvania Governor Josh Shapiro and U.S. Health Secretary Robert F. Kennedy Jr. over whether certain fatalities should be categorized as measles-associated. Pennsylvania reports a death as measles-associated if a person with confirmed measles dies within 30 days of developing symptoms, provided the death was not caused by an unrelated event.
In August, Pennsylvania reported two deaths of unvaccinated individuals. The CDC initially included these in the national tally but later removed them after Kennedy questioned if measles had caused or contributed to the fatalities. The CDC is currently working with the US Council of State and Territorial Epidemiologists to establish a standardized definition for reporting these deaths.
Misdiagnosis complicates containment efforts
An estimated 6.9 percent of patients with measles who sought medical care were misdiagnosed at least once in the two weeks preceding an accurate diagnosis, according to a study in Infection Control and Hospital Epidemiology. Researchers at the University of Iowa, led by biostatistician Alan T. Arakkal, PhD, identified 4,651 U.S. measles cases from 2001 through 2023 and estimated 381 cases were misdiagnosed, with a mean delay of just over four days.
Outpatient settings, such as doctor’s offices, accounted for 81 percent of missed cases. This compares to 14 percent in emergency departments and 3.9 percent in inpatient settings. The authors of the University of Iowa study noted that outpatient settings often have fewer infection control resources than hospitals.
The difficulty in identifying the disease early creates windows for further transmission. If someone goes to their doctor to be checked for measles, and they don’t recognize that they have measles, and then they walk out of the room, someone who comes in an hour and a half later can become infected with measles,
Dr. Handel explained.
Factors associated with misdiagnosis included patients under the age of two and those who received prescriptions for respiratory antibiotics. Researchers speculated that very young children might be harder to diagnose because they lack the language to describe their symptoms. Because the vaccine has been available for generations and the U.S. previously had years with fewer than 100 cases, some clinicians may not include measles in their differential diagnoses.
Serious complications follow infection
For every 1,000 unvaccinated children infected, an estimated one to three will die from neurologic and respiratory complications. Other potential long-term issues include permanent brain damage, sensory impairments like blindness or hearing loss, a compromised immune system, severe pneumonia, dehydration, and acute brain infections that can cause seizures. Dr. Handel noted that infections can lead to meningitis, where the virus infiltrates the spinal fluid. Children infected before one year of age can develop a progressive neurologic disease known as subacute sclerosing panencephalitis (SSPE), which can result in death up to 10 years later.
The current caseload is spread across 45 states and Washington, D.C. According to Yahoo News, approximately 96 percent of cases are among people who are unvaccinated or whose vaccination status is unknown. At the time of reporting, the CDC noted that only 2 percent of cases occurred in individuals who had received the recommended two doses of the measles, mumps, rubella (MMR) vaccine. An additional 2 percent of cases were among those who had received only one dose.
The CDC recommends two doses of the MMR vaccine: the first between 12 and 15 months of age, and the second between 4 and 6 years of age. According to the CDC, one dose is 93 percent effective, while two doses provide 97 percent effectiveness. While the vaccine is a primary tool for stopping outbreaks, some individuals—such as pregnant people, children with cancer, or those with compromised immune systems—may not be eligible for the vaccine. Parents should consult with a qualified healthcare professional to discuss family eligibility and concerns.
Earlier coverage: CDC Reports 5,182 Measles Cases, Highest Number Since 1991