The number of reported measles cases in the US has reached a 33-year high, with nearly 1,300 confirmed infections across the country as of Friday.

The data, released by John Hopkins University, marks a new milestone in an ongoing outbreak of the highly contagious, vaccine-preventable disease that was once thought to be eliminated in the US.

Measles cases have been reported in 38 states and the District of Columbia this year. At least three people have died from the illness, and 155 others were in hospital.

A vast majority of the measles cases - 92% - were in people who were either unvaccinated or whose vaccination status was unknown, according to the Centres for Disease Control (CDC).

The worst hit state is Texas, CDC data shows, where more than 700 cases have been reported. Other states with dozens of cases include Kansas and New Mexico.

Health officials say that measles spread is occurring mostly in neighbourhoods where vaccination rates are lower, such as Mennonite communities in Texas that opt out of modern medicine.

The outbreak comes as anti-vaccine sentiment in the US and elsewhere has grown in recent years.

Health Secretary Robert F Kennedy Jr had previously spread misinformation about childhood vaccinations and had minimised the outbreak. He later endorsed the measles, mumps and rubella vaccine as illness spread, saying in a post on X that it is "the most effective way to prevent the spread of measles".

Measles cases in the US were at their highest in recent memory in 1990, with nearly 28,000 reported infections, according to CDC data.

The illness was later declared eliminated around the year 2000, when cases sharply declined to less than 90 thanks to high vaccination rates and rapid outbreak response.

Cases started ticking up slightly in 2014 and again in 2019, when 1,274 confirmed infections were reported. But cases in 2025 have just surpassed that figure, with 1,277 infections now reported across the US.

Public health experts have said that the US will lose measles elimination status if there is continued spread of measles at the current rate for more than 12 months.

As a result of the current outbreak, more people are now getting the measles vaccine in the US. Between 1 January and 16 March, Texas gave at least 173, 000 measles doses compared to 158,000 in the same time period last year, state health department data shows.

The MMR vaccine is the most effective way to fight off the dangerous virus, which can lead to pneumonia, brain swelling and death. The jabs are 97% effective and also immunise against mumps and rubella.

Large measles outbreaks have been reported recently in other countries, including the UK. Last year marked the highest number of confirmed measles cases reported in England since 2012 at nearly 3,000.

Since January of this year, there had been 529 cases reported in England.

Canada is also experiencing a measles outbreak, with more than 3,000 cases reported in 2025 so far. The bulk of the cases are in the provinces of Ontario and Alberta.