A second child has died from measles as an outbreak of the highly contagious virus continues to grow in western Texas.

The school-aged child was not vaccinated, had no underlying health conditions and was in hospital suffering complications from measles, Aaron Davis, the vice-president of UMC Health System, told the BBC.

US Health Secretary Robert F Kennedy Jr, who has faced a backlash over his handling of the outbreak, visited Texas on Sunday in the wake of the death, which is the third overall in recent weeks.

The southern US state has reported more than 480 cases of measles so far this year as of Friday, a jump from 420 earlier in the week. The outbreak has extended to neighbouring states.

Across the whole of the US, more than 600 cases of measles have been recorded so far this year, more than double the 285 cases that the Centers for Disease Control and Prevention (CDC) recorded last year.

In 2019, there were a total of 1,274 measles cases recorded across the US, but prior to that there had not been a larger outbreak than this year's since the early 1990s, according to the CDC.

Many of this year's cases - nearly all in unvaccinated people - are related to the outbreak that began in western Texas.

"This unfortunate event underscores the importance of vaccination," Mr Davis said in a statement. "Measles is a highly contagious disease that can lead to serious complications, particularly for those who are unvaccinated."

The child - an eight-year-old girl - died early on Thursday.

The BBC contacted the state health department and the US Department of Health and Human Services for comment. Neither agency listed the death in their case counts on Friday.

In a statement posted on social media, Kennedy confirmed the girl's death.

"My intention was to come down here quietly to console the families and to be with the community in their moment of grief," he said in the statement.

He also said he was engaging with officials there to "support Texas health officials and to learn how our HHS agencies can better partner with them to control the measles outbreak". Kennedy said he was deploying a team - as he did in March - to help distribute vaccines, medications and other supplies, among other support services.

"The most effective way to prevent the spread of measles is the MMR vaccine," Kennedy wrote, referring to the measles, mumps and rubella jab.

In February, an unvaccinated six-year-old girl in the local Mennonite community was the first child to die of measles in the US in a decade. In March, an unvaccinated man died in New Mexico after contracting the virus, though his cause of death is still under investigation.

President Donald Trump on Sunday told reporters aboard Air Force One that he believes the outbreak is largely contained.

"It's so far a fairly small number of people, relative to what we're talking about," he said. "It's something that people have known about for many years. This is not something new."

"We'll see what happens. If it progresses, we'll have to take action. Very strong action," he said in response to a question from the BBC.

The virus - which can cause a fever, red rash, cough and other symptoms - is associated with a host of complications, including pneumonia, brain swelling and death.

The US declared measles eliminated from the country in 2000. But outbreaks have grown since then with a rise in anti-vaccine sentiment.

Two shots of the immunisation - proven safe - are 97% effective at preventing the virus and reduce severe infections. To achieve herd immunity - when enough of a group is immune to a disease, limiting its spread and protecting the unvaccinated - around 95% of the population must have the shots, experts say.

The recent outbreak originated in a religious community that strongly rejects vaccines. Local health officials in western Texas have told the BBC they have seen limited progress in attempts to improve vaccination rates.

Kennedy's early response to the worsening outbreaks was muted, drawing criticism from health experts.

Kennedy, a vaccine sceptic, initially described the situation as "not unusual".

He changed his approach after a child's died from measles in February - the first in the US in a decade - but stopped short of recommending that parents vaccinate their children. He instead encouraged them to talk to their doctors about the shot.

On Sunday, Senator Bill Cassidy, a Republican who represents Louisiana, called for stronger messaging. Cassidy is also a doctor and has previously criticised Kennedy for his sceptical attitude towards vaccination.

"Everyone should be vaccinated! There is no treatment for measles. No benefit to getting measles," Cassidy wrote on social media platform X. "Top health officials should say so unequivocally b/4 another child dies."

Kennedy has also at times promoted Vitamin A as a treatment for measles, which doctors say should only be provided in certain cases under the guidance of a physician.

In Lubbock, Texas, Covenant Children's Hospital has treated several children for Vitamin A toxicity after they were sent to the hospital for measles complications.