Dozens of people at two California universities have been quarantined as US health officials battle to stop the spread of a nationwide measles outbreak, authorities said on Thursday.
The Department of Public Health said hundreds of students and staff at the University of California Los Angeles (UCLA) and California State University (Cal State) had been exposed to a measles carrier earlier this month.
Those who couldn't prove they had been inoculated had been quarantined, it said.
"A Health Officer Order mandates the exposed person to remain at their residence, to notify Public Health if they develop symptoms of measles, and to avoid contact with others until the end of their quarantine period or until they provide evidence of immunity," the Los Angeles health department said in a statement.
The US has recorded 695 cases of measles in 2019 - the most in any year since the disease was declared eliminated at the turn of the century.
The surge comes amid a growing global movement against inoculation, with an estimated 169 million children missing out on the vital first dose of the measles vaccine between 2010 and 2017, according to a Unicef report.
The anti-vax phenomenon has adherents across the Western world but is particularly high profile in the US, where it has been fuelled by medically baseless claims spread on social media.
Measles is one of world's most contagious viruses. Spread by coughing or sneezing, the virus can linger in the air long after an infected person leaves a room.
In the latest cases, UCLA said an infected student had attended campus on three days earlier this month, coming into contact with about 500 people. Around 100 had been quarantined after they couldn't provide immunization records.
Cal State said 156 students and staff who may have been exposed to an infected student were quarantined.
Worldwide, measles cases rose 300 percent through the first three months of 2019 compared with the same period last year, according to the United Nations.AFP