Officials say the student is in his 20s and is from Contra Costa County, where he still lives. They say he was not vaccinated and was likely infected with measles during a recent trip abroad in Asia.
Before being diagnosed, the student used public transportation for several days and attended class in Berkeley.
The measles virus can stay in the air for up to two hours. Officials say the man traveled between El Cerrito del Norte and Downtown Berkeley stations from Tuesday, Feb. 4 to Friday, Feb. 7 between 8 a.m. to 10 a.m. and in the afternoon/evening commute hours.
Health officials say those who are vaccinated or have had the disease before are unlikely to catch measles, even if they had contact with the contagious person. Those who have not been vaccinated are likely to catch the disease if exposed to the virus.
They urge anyone who shows symptoms of measles to contact their healthcare provider immediately.
"Measles is a serious, highly contagious disease," said Dr. Janet Berreman, health officer for the City of Berkeley. "It spreads through the air, when an infected person coughs or sneezes. Fortunately, the measles vaccine is highly effective in preventing infection."
Measles symptoms can begin one to three weeks after exposure and can include high fever, runny nose, coughing and watery red eyes. A rash develops on the face and neck two to three days after the fever begins, and spreads down the body. The rash usually lasts five or six days. An infected person is contagious for several days before and after the rash appears.
Health officials stress that measles can be more serious to certain groups of people. For example, it could cause deafness. Children and babies are very vulnerable. It could also cause encephalitis and also miscarriage in pregnant women.
This is only the second case of measles in Contra Costa County in five years.
UC Berkeley will be offering the vaccine to any student on campus who has not been vaccinated.
For more information about measles, visit cchealth.org/measles. Contra Costa County residents can also call 925-313-6740 or 211. City of Berkeley residents can call 510-981-5300. Additional also information is available at cdc.gov/measles/index.html.
(ABC7 News reporter Lyanne Melendez contributed to this report)