The United States has recorded more than 5,000 cases of measles in a single year for the first time in 35 years, according to new figures released by the country's leading public health agency. The Centers for Disease Control and Prevention (CDC) said 5,182 confirmed cases had been reported across the country so far in 2026, a total not seen since 1991 and more than double the number recorded in all of 2025.
Measles is a highly contagious viral illness that spreads through the air when an infected person coughs or sneezes, and it can linger in the air for up to two hours after they leave a room. It is also one of the most preventable diseases in medicine: two doses of the measles, mumps and rubella (MMR) vaccine are about 97 per cent effective. That is why health officials on both sides of the political divide have treated the scale of this year's outbreak as a warning sign rather than a statistical curiosity.
The latest weekly update, released on Friday, showed the national count rising by 330 cases in a single week, a jump of 6.8 per cent from the 4,852 cases reported in the previous update. The CDC said 4,993 of the cases recorded so far this year were linked to outbreaks, and 43 new outbreaks had been reported in 2026. The agency publishes its updated national count every week, so the final total for the year is expected to keep climbing while the outbreaks continue.
The contrast with last year is stark. In 2025 the CDC recorded 2,289 confirmed cases over the full twelve months, a figure that was itself considered high at the time. This year's tally passed that total months ago and has now more than doubled it, with almost two months of the year still to go. The last time the United States saw a larger annual measles count was in 1991, when the disease was still circulating far more widely before vaccination coverage reached the levels of recent decades.
Almost all of the people who have fallen ill this year were either unvaccinated or had an unknown vaccination status, accounting for about 96 per cent of cases, according to the CDC's data. Children and teenagers have borne the brunt of the outbreak, making up nearly 60 per cent of confirmed cases. Children under five accounted for 18 per cent of cases, while those aged between five and 19 made up 41 per cent. Hospital admissions linked to measles stood at 562, about 11 per cent of all reported cases.
Pennsylvania has been the hardest-hit state by a wide margin. Its health department has reported 1,487 cases this year, and the state has also recorded the largest number of deaths. South Carolina, with 670 cases, and Utah, with 536, have the next-highest totals. The disease has been reported in dozens of states, and the pattern of spread has followed the gaps in vaccination coverage, with outbreaks taking hold in communities where immunisation rates have fallen.
The death toll has become a point of dispute between federal and state health authorities. The CDC's national tally lists four measles-associated deaths in 2026, while state health departments have reported at least eight, including among very young children. The gap arose after the CDC, under Health Secretary Robert F. Kennedy Jr., changed the way it counts measles deaths, switching from figures supplied by state health departments to mortality data from the National Center for Health Statistics. The CDC has said it is working with the Council of State and Territorial Epidemiologists to agree on a standard definition for a measles death.
One of the deaths reported this week was that of a seven-month-old child in New York, the state's first measles death in more than 30 years. The child died on Monday, and the case has drawn attention to the risks for babies too young to receive their first dose of the MMR vaccine, who rely on the immunity of the people around them. Health experts have repeatedly warned that when vaccination rates fall, infants and people with weakened immune systems are the first to be put at risk.
Behind the case numbers lies a steady erosion of routine immunisation. The kindergarten vaccination rate in the United States fell from 95.2 per cent in the 2019-20 school year to 92.4 per cent in 2025-26, according to figures cited by Bloomberg, below the 95 per cent threshold that epidemiologists say is needed to maintain herd immunity against measles. Because the virus is so infectious, even small dips in coverage can allow it to spread quickly once it is introduced into a community, and that is what appears to have happened repeatedly this year.
The stakes go beyond this year's case count. The United States was declared to have eliminated measles in 2000, meaning the disease was no longer spreading continuously within the country, and health officials have warned for months that the status is now in jeopardy. The Pan American Health Organization, the regional arm of the World Health Organization, is due to reassess the position next week, at a meeting from 10 to 13 November, when the United States is widely expected to lose its elimination status if transmission is judged to have continued for a year.
For now, the CDC's message to the public has remained unchanged: vaccination is the protection that works. Health officials have urged parents to check that their children's immunisations are up to date and have advised anyone unsure of their vaccination status to speak to a doctor, particularly before travelling. With the weekly counts still rising and the winter months ahead, when respiratory viruses typically spread more easily, the coming weeks will show whether the outbreak is finally slowing or whether 2026 will end with a still larger total.
