Breaking News Emails

Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Health officials are warning about a second unvaccinated California college student who may have exposed thousands to measles on public transportation even as cases of the highly contagious disease have reached 115 nationwide.

A University of California, Berkeley, student has been isolated after tests confirmed measles Friday, Berkeley public health officials said. The student returned on a domestic flight to Oakland on March 30, and then rode the Bay Area Rapid Transit system, or BART, to class from April 1 to April 3.

BART transports about 400,000 riders each weekday.

In February, an unvaccinated UC Berkeley student who traveled to the Philippines returned home and infected two other relatives with measles, as well as exposing people on BART and in class, health officials said.

At least 51 cases of measles have been reported in California so far this year, far outpacing the four cases reported in all of 2013. Nationwide, 115 cases have been reported in the first four months of 2014 after at least 175 cases were reported last year, officials with the Centers for Disease Control and Prevention said Monday.

People who previously had measles or who have been vaccinated are immune to the infection. But in recent years, pockets of people who delay or avoid childhood vaccines including measles have contributed to growing outbreaks, CDC officials said.

Measles is a highly contagious virus that lingers in the air for up to two hours when someone coughs or sneezes. About 90 percent of people who are not immune to measles will contract the infection if they’re exposed.

Symptoms include high fever, runny nose, cough and watery red eyes, as well as a rash on the face, neck and body.

Measles was considered eradicated in the U.S. in 2000, but there’s been a recent uptick in cases caused by travelers who become infected abroad and then spread the disease to vulnerable people back home.