A measles outbreak in West Texas has exceeded 120 cases and resulted in the first US death from the illness in a decade.
The Texas Department of State Health Services reported the death of a "school-aged child" who was hospitalised in Lubbock, Texas.
Officials said the child was not vaccinated.
The last time a person died of measles in the US was in 2015, according to the Centre for Disease Control and Prevention (CDC).
At least 124 people are known to be infected in West Texas since early February, across nine counties.
Almost all cases — 101 — were in patients aged 17 or younger and all but five of them were unvaccinated.
The outbreak has mostly been concentrated in a religious community in Gaines County, where almost 14 per cent of schoolchildren have an exemption from the vaccine.
Texas laws allow vaccine exemptions for reasons of conscience, including religious beliefs.
Children in the "close-knit, under-vaccinated" rural Mennonite community are also largely home-schooled.
Peter Hotez, director of the Center for Vaccine Development at Baylor University, in Waco, Texas said the outbreak would accelerate for a while.
"It's a bad illness," Dr Hotez said.
"Unfortunately, Texas is the epicentre of it because of our very aggressive anti-vaccine movement."
An additional nine cases were announced on Tuesday, in eastern New Mexico, which is along Texas' north-west border.
New Mexico's health department warned that "because measles is so contagious, additional cases are likely to occur".
According to the CDC, measles cases have also been found in Alaska, California, Georgia, New Jersey, New York City and Rhode Island.
What has health secretary RFK Jr said?
During a meeting with President Donald Trump's cabinet at the White House, Robert F Kennedy Jr appeared to downplay the seriousness of the measles outbreak.
"We are following the measles epidemic every day," he said.
"Incidentally, there have been four measles outbreaks this year.
"In this country last year there were 16. So, it's not unusual. We have measles outbreaks every year."
Kennedy also said that two people had died in the Texas outbreak.
However, Katherine Wells, director of public health at the health department in Lubbock, said that there had been just one measles death in Texas so far.
If a second death did exist, Lubbock's city spokesperson said, "we'd know about it".
RFK Jr has a long record of any-vaccine advocacy, which he was repeatedly grilled over during his Senate confirmation hearing last month.
In 2023, he falsely said "there's no vaccine that is safe and effective".
He's also falsely linked the MMR (measles- mumps-rubella) vaccine to autism, a claim debunked by scientific research.
But during the hearing, he told lawmakers that he was not anti-vaccine and believes vaccines "play a critical role in healthcare".
Vaccination rates decline
Measles was considered eliminated in the US in 2000, because of the widespread use of the MMR vaccine.
But as vaccine hesitancy increased over time, fewer children received their shots.
In 2023, the share of children exempted from vaccine requirements in the US rose to 3.3 per cent, up from 3 per cent the year before. Overall 92.7 per cent of kindergarteners got their required shots.
Before the COVID-19 pandemic, the vaccination rate was 95 per cent, a coverage level that makes it unlikely that a single infection will spark a disease cluster or outbreak.
Health officials say that although the changes seem slight, it translates to about 80,000 kids not getting vaccinated.
In 2024, there were 285 cases of the disease in the US from 16 outbreaks, up from 59 cases from four outbreaks in 2023.
In Australia this year, 18 cases of measles have been reported through the Australian Government's National Communicable Disease Surveillance Dashboard.
According to the Department of Health, 92.21 per cent of two-year-olds received the MMR vaccine in the 2024 September quarter.
To achieve herd immunity for infectious diseases, such as measles, the Department of Health says a coverage rate of 92-94 per cent is required.
What is measles?
Measles is a highly contagious, airborne virus that infects the respiratory tract and then spreads throughout the body.
According to the World Health Organisation (WHO):
Measles spreads easily when an infected person breathes, coughs or sneezes. It can cause severe disease, complications, and even death.
Measles can affect anyone but is most common in children.
Symptoms can include a red blotchy rash, high fever, cough and runny nose. They typically appear anywhere from seven to 14 days after exposure to the virus.
ABC/wires
