US measles cases have passed 5,000 in a single year for the first time in 35 years, according to the Centers for Disease Control and Prevention, as the outbreak claimed a third life this week. The CDC counted 5,182 confirmed cases as of November 5, the most since 1991 and more than double the total recorded in all of 2025.
The latest fatality was an unvaccinated infant in Wisconsin, the third measles death reported in the United States in a single week. Cases have now been reported in 45 states plus Washington, DC, with 330 new cases in the most recent week alone, underscoring how quickly the virus is spreading.
Measles was declared eliminated in the United States in 2000, meaning the disease no longer spread continuously within the country. The current surge is the worst since that milestone and has alarmed public health officials, who say the outbreak was preventable.
Why US measles cases are surging
Measles is one of the most contagious viruses known to medicine. A single infected person can spread it to as many as nine out of ten unvaccinated people they come into close contact with, and the virus can linger in the air for up to two hours after an infected person leaves a room.
Public health experts point to falling vaccination rates as the main driver of the outbreak. The measles, mumps and rubella (MMR) vaccine is highly effective, with two doses providing about 97 percent protection, but coverage among young children has slipped in many communities in recent years.
Kindergarten vaccination rates have declined in dozens of states, and exemptions have risen. When vaccination coverage in a community falls below roughly 95 percent, the virus can find enough susceptible people to keep spreading, and outbreaks can take hold.
The CDC has warned that the 2026 total is already more than double the whole of 2025, and the pace of new cases shows little sign of slowing as the year draws to a close.
The human cost of the outbreak
The death of an unvaccinated infant in Wisconsin this week was the third measles fatality reported in seven days, a grim marker of how serious the disease can be for the youngest and most vulnerable patients.
Measles is often thought of as a childhood rash, but it can cause severe complications, including pneumonia, brain swelling, and death. Infants too young to be vaccinated and people with weakened immune systems are at the greatest risk.
Hospitals in outbreak areas have reported a rise in admissions of children with measles complications, and health departments have been tracing contacts, setting up vaccination clinics, and urging parents to check their children’s immunisation records.
The CDC recommends two doses of the MMR vaccine, the first at 12 to 15 months of age and the second at four to six years. Adults who are unsure of their vaccination status are also advised to check with their healthcare provider.
Measles in schools and travel
The outbreak has also disrupted schools. In several states, unvaccinated children have been excluded from school during outbreaks, and health departments have sent letters to parents urging them to check immunisation records before the winter term. Schools are a common setting for measles transmission because the virus spreads so easily in crowded indoor spaces.
Health officials have also warned travellers, since measles remains common in many parts of the world. Anyone planning international travel is advised to confirm they are fully vaccinated at least two weeks before departure, and families with infants should ask their doctor about an early dose if travelling to an area with an active outbreak.
What health officials are doing
State and local health departments have stepped up their response, with vaccination drives, public warnings, and school exclusion policies for unvaccinated children in outbreak areas.
Health Secretary Robert F. Kennedy Jr. has faced scrutiny over the administration’s handling of the outbreak. This week, Kennedy also proposed expanding access to six unapproved peptides and said he had personally used one of them, BPC-157, for a muscle injury, comments that drew attention away from the measles response.
Public health officials say the most effective response remains straightforward: get more people vaccinated. The vaccine is safe, widely available, and has been used for decades, and health departments are offering it free or at low cost in many areas.
Parents and caregivers who are unsure whether their children are protected can contact their doctor or local health department to check their records and arrange vaccination if needed.