US measles cases pass 5,000 in 2026, the highest annual total since 1991

The United States has recorded 5,182 confirmed measles cases in 2026, according to the Centers for Disease Control and Prevention (CDC). It is the largest annual count since 1991. State health officials have reported at least eight measles-related deaths, including among very young children.

The numbers in context

The 2026 total is already more than double the 2,289 cases logged across the whole of 2025. The CDC figure is a count of confirmed cases, and the year is not yet over, so the final total will be higher. The source report does not break the cases down by age, state or vaccination status. Those details, which surveillance teams usually publish separately, will shape how researchers interpret the surge.

Measles was declared eliminated from the US in 2000, a result attributed to sustained vaccination. Public health specialists link its return in recent years to falling vaccination coverage and growing distrust of health authorities.

Why measles spreads so easily

Measles is among the most transmissible human pathogens. Its basic reproduction number is commonly put at 12 to 18, far higher than that of most respiratory viruses. Population immunity of around 95 per cent is generally considered necessary to stop sustained spread. Two doses of the measles, mumps and rubella (MMR) vaccine give very high individual protection, but small pockets of low coverage can still sustain outbreaks even when national averages look reassuring.

That is why the disease often acts as an early indicator of weakening immunisation programmes. Clusters tend to appear first in communities with low uptake and then spread outwards.

Clinical burden

The illness causes fever, respiratory symptoms and a characteristic rash. Some patients develop pneumonia or brain inflammation, which can lead to serious long-term damage or death. Before the vaccine arrived in the early 1960s, measles killed hundreds of American children each year. Worldwide it still causes tens of thousands of deaths annually.

Adam Ratner, a paediatric infectious disease specialist, told AFP that the deaths are "tragic, and they are completely preventable". He also noted that the burden falls on children, who have no say in the vaccination decisions made for them. The source report adds that US Health Secretary Robert Kennedy Jr. has been criticised for spreading misinformation about the vaccine and playing down the disease. That criticism is reported as an accusation, and the source gives no data on how much any such messaging has affected uptake.

What researchers will be watching

Several questions follow from the figures. Epidemiologists will want to know how much of the rise reflects a few large outbreaks and how much reflects widespread local transmission. They will also look at how far vaccination coverage has fallen at county and school level, and whether case counts are being understated because of under-diagnosis or delayed reporting, a common problem when a disease has been rare for years.

Further CDC updates and state-level data should clarify the age distribution of cases, the proportion that were unvaccinated and the hospitalisation rate. These details matter for modelling future outbreaks and for judging whether the country can regain and keep its elimination status. That status depends on halting continuous transmission, not simply on lowering case numbers.

Source: US reports highest number of measles cases in 35 years (Medical Xpress, 7 November 2026).

Image: AI-generated illustration.