The order was issued at UCLA and Cal State LA for students and employees exposed to confirmed measles and who can not prove that they have been vaccinated against highly contagious disease.
Those students and university workers, counting more than 100, they were ordered to stay at home, avoid contact with others and report public health officials if they develop symptoms.
"The two universities are helping to implement quarantine orders and determine how best to support students who must be quarantined and living on campus," the Los Angeles Public Health Department said.
US Centers for Disease Control and Prevention confirmed Wednesday a milestone, saying the agency had counted 695 cases in 22 countries this year.
A Los Angeles health report says the measures at both universities are being conducted "to build awareness among students, faculties and staff about measles risks after potential measles exposure."
"Quarantine for measles can be up to 21 days from the day of the last exposure, with the exposed person no longer a risk of developing the disease and spreading measles to others," the statement said.
Smallpox is a highly contagious disease caused by a virus that can spread through the air when the infected person coughs or sneezes, or someone comes in direct contact or shares bacteria by touching the same objects or surfaces. Symptoms of chickenpox may include fever, cough, runny nose, watery eyes, and reddening rash.
Smallpox can stay in the air for up to two hours after a sick person coughs or sneezes and can stay on surfaces for many hours, making the college campus particularly vulnerable to the disease due to the spread of people from and out of buildings.
In a letter to students and faculty, UCA's Chancellor Jen Block said the university was notified on Monday that a student had measles. The student attended classes at Franz Hall and the Boehler Hall for three days – on April 2, 4 and 9 – while he was infected, Blok said.
"After learning about this incident, UCLA instantly identified and reported more than 500 students, faculty and staff with whom the student can come in contact or who may have been exposed," Blok said. "They were also given detailed information on treatment and prevention."
Most people have been cleared, the chancellor said, "but we are still waiting for medical records from 119 students and eight faculty members to determine whether they are immune to measles."
"We expect that they will be quarantined for 24 to 48 hours until their immunity is established," Blok said. "Some may need to quarantine for up to seven days. We found that those living on campus should be taken care of in Los Angeles while quarantined."
In Cal State LA, school officials said there could be exposure to measles in the North Library on April 11, between 11 am and 3 am.
Library employees, including student workers, "were sent home under quarantine orders and were told to stay home and avoid contact with others as much as possible," the university said.
The university did not say how many people were quarantined.
"The Department of Public Health finds that at this time there is no known current risk associated with measles in the library," the university said.
Meanwhile, state public health officials on Thursday urged residents of California to ensure they were vaccinated against measles before the trip, especially in international locations.
The number of cases of measles in California has risen by more than doubled over the past week, from 15 to 38, the California Public Health Ministry said. There were a total of 11 cases this time last year.
From 2019 cases, 14 cases were with international travelers, 22 cases were to be diverted from passengers to persons in California, and two cases were from an unknown source, the agency said.
Health officials also said that a passenger flying to and from Los Angeles Airport on April 18 is confirmed with a measles case, a fourth such case at the airport.
"Vaccination is the only way to make sure that you and your family members will not get measles," says Dr Karen Smith, director of the Public Health Department in California. "Many countries currently have widespread measles activity. Make sure you and your family are fully vaccinated before traveling internationally."