Measles Cases Surge in U.S. and UK Amid Declining Vaccination Rates

Measles cases have surged significantly in the U.S., with 2,280 confirmed cases in 2025—the highest levels since 1991. As of February 19, 2026, there have already been 982 confirmed cases this year. Many of these cases are currently localized in states with large outbreaks—Arizona, Utah, and South Carolina.

The surge is driven by declining MMR vaccination rates, increased international travel, and pockets of low herd immunity. Because measles is highly contagious, a single infectious person can potentially infect 18 others, putting even people living in non-affected areas at risk.

In north London, at least 34 children have contracted measles in Enfield so far this year, with a number sent to hospital. Unvaccinated pupils identified as close contacts of people with measles could be excluded from school for 21 days in accordance with national guidelines, Enfield Council said in a letter to all parents in the borough in late January. Infections had been confirmed in "at least" seven schools in Enfield and neighbouring Haringey. Some 60 suspected cases had been confirmed—with the majority in schools and nurseries and some children requiring hospital treatment, "particularly those who have not been immunised."

The UK recently lost its World Health Organization measles elimination status after over 2,900 cases of measles were confirmed in England in 2024, the highest level for more than a decade. There were nearly 1,000 cases in 2025.

Philadelphia officials responded to a confirmed measles case involving a person who travelled through Philadelphia International Airport last week. The exposure was listed as Feb. 12 from 1:35–4:30 p.m. at terminal E. Anyone who was in that location during the listed times is advised to monitor for symptoms and check to see if they're immune to the disease.

To quickly notify the public of potential exposure sites and prevent further spread, health authorities issue measles exposure alerts—often delivered via news releases and social media—identifying specific locations, dates, and times where an infectious person was present. These alerts are designed to halt or prevent potential outbreaks. A legitimate measles alert will come from official public health sources, such as local or state health departments or the CDC.

Measles is spread from person to person, commonly transmitted through close contacts—through droplets when a person coughs or sneezes, for example—and is inactivated by ultraviolet light and heat. It can remain infectious while suspended in the air, or survive on surfaces, for up to two hours. The infectious disease is so contagious that 90% of unvaccinated people exposed to it wind up contracting measles.

Two doses of the measles vaccine provide 97% lifelong protection against the disease, and one dose provides 93% protection. People born before 1957 are also protected, because almost everyone born before that year was exposed to wild type measles virus. Measles vaccines were not available until 1963.

Just 64.3% of five-year-olds in Enfield received both doses of the MMR (measles, mumps and rubela) vaccine in 2024/25—one of the lowest rates in the country and far below the 95% threshold needed to prevent outbreaks. National uptake was 84.4% that year, down from a high of 88.8% a decade ago.

Common measles symptoms include high fever, cough, runny nose, and watery, red eyes. Some people may develop a flat, reddish-brown facial rash that eventually spreads to the neck, torso and rest of the body. When the rash appears, a person's fever may spike to more than 104 degrees Fahrenheit. Symptoms tend to appear a week or two after infection.

Other signs and symptoms of measles include loss of appetite and diarrhea, and Koplik spots, tiny white spots that may appear inside the mouth two to three days after symptoms begin. Small raised bumps may also appear on top of the flat red spots (the spots may become joined together as they spread from the head to the rest of the body).

People are most contagious about four days before the rash appears and for about four days afterward. During this time, infected individuals should quarantine.

Individuals are considered immune if they received two doses of MMR vaccine, were born before 1957, or have documentation of a past measles infection. Anyone whose received only one dose of MMR vaccine is still considered protected against measles and usually won't need to stay home away from others after an exposure, but a second dose may be needed.

Anyone who isn't immune to the measles—especially those who are pregnant, have a weakened immune system or if their infant is less than 1 year old—should call their health care provider or pediatrician immediately after exposure and ask if they qualify for post-exposure treatment, which can help prevent measles. They should stay home (quarantine) and monitor symptoms for 21 days after exposure.

Before the measles vaccine was introduced, an estimated 48,000 people were hospitalized and 400–500 people died in the United States each year. By 2000, measles was declared eradicated in the U.S. thanks to a high percentage of people receiving the MMR vaccine. More recently, however, measles activity in the U.S. has increased, which was attributed to MMR coverage among kindergarteners dropping below 95% and a rise in global cases.