More than 150 unvaccinated schoolchildren are being quarantined for 21 days in South Carolina after being exposed to measles, state officials said.

Because the students who were exposed did not have immunisations, they were forced to miss school during the period of potential disease transmission.

South Carolina is the latest US state to experience a measles surge this year after outbreaks in New Mexico and Texas, where hundreds were infected and three people died.

So far this year, the US has confirmed 1,563 cases, the highest level nationwide in more than 30 years, according to the Centres for Disease Control and Prevention (CDC).

The quarantined children come from two schools in Spartanburg County, South Carolina - Global Academy of South Carolina and Fairforest Elementary. One school serves primary-age children and the other serves students in primary and secondary school.

The South Carolina Department of Public Health reported its eighth confirmed measles case in two weeks on Thursday, in Greenville County, in the northern part of the state.

"What this case tells us is that there is active, unrecognised community transmission of measles occurring in the Upstate, which makes it vital to ensure that the public has received their measles vaccinations," a department release said.

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

In addition to the outbreak in South Carolina, cases are on the rise in Utah and Arizona, where 55 and 63 cases have been reported, respectively.

Earlier this year, hundreds of people were infected with measles in West Texas and New Mexico in an outbreak that killed two Texans and one person in New Mexico. Those deaths jolted a country that had not recorded a measles death since 2015.

A majority of reported cases have been in those who are unvaccinated.

Further north, large numbers of measles have been reported across Canada, particularly in the provinces of Alberta and Ontario.

The country has logged 5024 cases, the government said, more than three times the number in the US, despite Canada's far smaller population.

The data has raised questions about why its spreading so quickly there and whether Canadian authorities are doing enough to contain it.

In the US, the increase in measles has been linked in part to vaccine sceptics like Health Secretary Robert F Kennedy Jr - although he has endorsed the measles vaccine as safe. But Canada does not have a prominent RFK Jr-like figure in public health.

And it's not just the US and Canada. Measles cases are spiking globally, according to UNICEF. In the past five years, 100 countries have seen outbreaks.