Health officials said Friday that nearly 700 people at two universities in Los Angeles have been ordered to stay home because they might have had contact this month with two measles patients.
At one point, roughly 1,700 people were under quarantine orders, but by Friday health officials had cleared more than 1,000 who had come forward with proof of vaccination, Los Angeles County public health officials said at a news conference.
The highest number of actively quarantined people, 628, was connected to Cal State Los Angeles, where a single measles patient created hundreds of possible exposures by visiting a campus library, officials said. That number includes at least 106 staff members, according to the university.
"We also issued a blanket order that asked anyone who had been in the library, on 4/11 between 11 and 3 to self-quarantine, notify health services and establish that they were immune before they exposed themselves to the public," said Barbara Ferrer, Los Angeles County's public health director.
Across town at UCLA, 853 students and seven faculty members might have been exposed to one measles patient, she said. Health officials verified immunization for hundreds, leaving 45 students and one faculty member under quarantine Friday, Ferrer said.
Related: Treatment, preventative care and vaccinations for measles across the world
Treatment, preventative care and vaccinations for measles across the world
Treatment, preventative care and vaccinations for measles across the world
A child receives a vaccination against measles by a family physician on April 16, 2018 in the Romanian capital, Bucharest.
Measles still claims young lives in Romania, where nearly 40 children have died in an outbreak that many blame on parents being misled by scare stories that vaccinating them is dangerous. Some 12,000 people have contracted measles since late 2016 in the European Union's second-poorest country, 46 of them died. Among the dead, 39 were children under the age of three who had not been vaccinated, making Romania one of the worst affected countries in the ongoing measles outbreak in Europe. / AFP PHOTO / Daniel MIHAILESCU (Photo credit should read DANIEL MIHAILESCU/AFP/Getty Images)
A family physician prepares a measles vaccine during a consultation on April 16, 2018 in the Romanian capital, Bucharest. - Measles still claims young lives in Romania, where nearly 40 children have died in an outbreak that many blame on parents being misled by scare stories that vaccinating them is dangerous. Some 12,000 people have contracted measles since late 2016 in the European Union's second-poorest country, 46 of them died. Among the dead, 39 were children under the age of three who had not been vaccinated, making Romania one of the worst affected countries in the ongoing measles outbreak in Europe. (Photo by Daniel MIHAILESCU / AFP) (Photo credit should read DANIEL MIHAILESCU/AFP/Getty Images)
A nurse was seen vaccinating school children at her school in Lhokseumawe, August 4, 2018, Aceh, Indonesia. Vaccination Measles-Rubella (MR) for Indonesian school children is part of the Indonesian government's health program to provide physical immunity from two dangerous diseases, Rubella and Measles in Indonesian children. (Photo by Fachrul Reza/NurPhoto via Getty Images)
Artists wearing superhero costumes comfort an elementary student while she receives a German Measles, also known as Rubella, vaccination in Pekanbaru, Riau province on August 1, 2018 as part of the Indonesian governments health program to combat childhood diseases. (Photo by WAHYUDI / AFP) (Photo credit should read WAHYUDI/AFP/Getty Images)
ALEPPO, SYRIA - APRIL 17 : A Syrian child is vaccinated during the measles campaign in Al-Bab district of Aleppo, Syria on April 17, 2018. Kids fled from Eastern Ghouta's Douma after Assad regime forces' suspected chemical attack on April 7, 2018 receive measles vaccine Al-Bab district of Aleppo. (Photo by Omer Alven/Anadolu Agency/Getty Images)
A Venezuelan woman is vaccinated against measles in Cucuta, Colombia, at the international brigde Simon Bolivar on the border with Venezuela, on March 21, 2018. / AFP PHOTO / Schneyder Mendoza (Photo credit should read SCHNEYDER MENDOZA/AFP/Getty Images)
Venezuelan, Yan Manuel, receives a free measles vaccine given by a volunteer, after showing his identity card at the Pacaraima border control, Roraima State, Brazil August 19, 2018. REUTERS/Nacho Doce
A member of the Free Revolutionary Police carries out an inspection on a measles vaccine in the southern Idlib countryside September 17, 2014. Fifteen children died after being vaccinated against measles in northern Syria, resulting in the programme being halted, aid workers said on Wednesday, a tragedy likely to damage trust in health services in opposition-held areas. The Free Revolutionary Police is a newly launched unarmed police movement that works in areas controlled by the Free Syrian Army to solve the day-to-day problems in Idlib, the group said. Picture taken September 17, 2014. REUTERS/Khalil Ashawi (SYRIA - Tags: CIVIL UNREST CONFLICT HEALTH)
A girl receives anti-measles vaccination drops at a health centre in BASECO compound in Tondo, Manila September 3, 2014. Philippine President Benigno Aquino said on September 1, 2014 between 11 to 13 million people in the country are at risk from measles, polio and rubella (German measles), and asked the public to cooperate in eradicating the preventable diseases, during Monday's launch of a mass national vaccination campaign against measles and polio, reported local media. REUTERS/Erik De Castro (PHILIPPINES - Tags: HEALTH SOCIETY)
A vial of measles, mumps and rubella vaccine and an information sheet is seen at Boston Children's Hospital in Boston, Massachusetts February 26, 2015. REUTERS/Brian Snyder (UNITED STATES - Tags: HEALTH)
Rowan Walters, aged four, is held by her mother as she given an MMR injection at the Paediatric Outpatients department at Morriston Hospital in Swansea, south Wales April 6, 2013. Following an increase in the number of confirmed cases of a measles in south Wales, parents in the area were urged to vaccinate their children, and hospitals in the region opened drop-in clinics on Saturday, local media reported. REUTERS/Rebecca Naden (BRITAIN - Tags: SOCIETY HEALTH)
A health worker in Ciudad Juarez at the Mexican border crossing with El Paso, Texas, hands out leaflets to passing motorists and people as part of a measles prevention programme, February 16, 2015. California public health officials have confirmed three more cases of measles in an outbreak that began in late December, bringing to 113 the total number of people believed to have been infected in the state. Health officials in Arizona, where seven cases of measles have been documented, said the outbreak would likely be considered over in that state if no further infections were reported over the weekend. Across the United States, more than 150 people have been diagnosed with measles, many of them linked to an outbreak that authorities believe began when an infected person from out of the country visited Disneyland in late December. REUTERS/Jose Luis Gonzalez (MEXICO - Tags: SOCIETY HEALTH IMMIGRATION)
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The scare is part of a nationwide burst of measles outbreaks in California, New York state, Washington, New Jersey and Michigan, according to the U.S. Centers for Disease Control. In a statement CDC officials blamed "an increase in the number of travelers who get measles abroad and bring it into the U.S., and/or further spread of measles in U.S. communities with pockets of unvaccinated people."
Federal health officials say the number of confirmed measles patients in the United States — 626 in 22 states — is on pace to surpass 2014's record 667 cases. One in 1,000 children who contract the disease will die, according to the CDC.
In Los Angeles County, health officials said international travelers, healthcare workers and those who care for young children should consider a second vaccination. One of the confirmed university cases "did travel internationally prior to coming down with measles," Ferrer said.
There have been five cases of measles in Los Angeles County so far this year, she said.
On Friday, President Donald Trump urged parents to get their children vaccinated.
"This is really going around now, they have to get their shot," he said.
At a 2015 presidential debate, Trump appeared to buy into the claim, discounted by science, that there's a link between childhood vaccination and autism.
"Autism has become an epidemic … I am totally in favor of vaccines," he said at the time. "But I want smaller doses over a longer period of time."
Earlier this year, Michelle Mello, a professor of health research and policy at the Stanford School of Medicine, said in a university Q&A that "one of the most frustrating aspects of this issue for health scholars is the persistence of mistaken beliefs about vaccine risks, which are often traceable to a discredited and retracted study about vaccines and autism.
"As a parent," she continued, "I sleep better knowing my kids are immunized."