More than 700 students and staff members at two California universities were under quarantine on Friday — an increase of about 400 from the day before — as officials continued steps to curb the potential spread of measles after an outbreak was declared in Los Angeles County.
The two universities — the University of California, Los Angeles, and California State University, Los Angeles — have been working with county health officials to identify and contact students and employees who may have been exposed to measles this month.
Those at risk of having contracted measles were given health officer orders — legal orders issued by county officials — to stay home and avoid contact with others as much as possible.
Measles is an extremely contagious virus that can cause serious respiratory symptoms, rash and fever. In some cases, especially in babies and young children, the consequences can be severe.
As of Thursday, the two universities had reported a total of 280 students and faculty members under quarantine.
In updates on Friday, that number had been revised to more than 700, with the increase coming at California State-Los Angeles.
That university reported that 106 staff members and 550 students were under quarantine orders. That was a change from the 127 staff members and 71 students reported on Thursday.
The revision in numbers came because “people who were potentially exposed have been coming to our Student Health Center in stages since Thursday morning to be screened,” Robert Lopez, a spokesman, said.
“Some were cleared immediately,” he said. “Others were told they were under quarantine.”
As of Friday afternoon, 110 students and 21 staff members had been cleared, he said. It was not clear whether those people were ever under a quarantine, Mr. Lopez said.
U.C.L.A. said in a statement on Friday that one student remained under quarantine and that less than 50 were self-isolating in off-campus residences. That total was down from 76 quarantined students on Thursday.
In a statement on Friday, the Los Angeles County Department of Public Health described the number of health officer orders for quarantine as “dynamic.”
The department said it lifts a quarantine order as soon as documents are provided showing that a person has been fully immunized against measles or has a lab test that verifies immunity.
The quarantine period for the potential exposure at U.C.L.A. ends on Tuesday, and at California State-Los Angeles on Thursday.
At U.C.L.A., a student who had contracted measles attended classes in two university buildings on three days while contagious, Chancellor Gene D. Block said in a statement on Wednesday.
The Public Health Department believes that additional measles exposures may have occurred this month at Los Angeles International Airport and at several restaurants near Glendale.
A single case of the measles can quickly spiral into an outbreak, especially because people might not know they have the illness for several weeks before they begin to show symptoms.
Los Angeles is the latest metropolitan area to be hit by measles, as part of a national surge in cases. On Wednesday, federal health officials said the number of measles cases in the United States had risen to 695, the highest annual number recorded since the disease was declared “eliminated” in the country in 2000.
The virus mostly has affected families that do not vaccinate their children, and the Centers for Disease Control and Prevention has blamed “organizations that are deliberately targeting these communities with inaccurate and misleading information about vaccines.”
