BART rider with measles potentially exposed thousands

Passengers are seen aboard a train as it prepares to leave the Fruitvale BART station in Oakland, CA, Friday, January 31, 2014. Passengers are seen aboard a train as it prepares to leave the Fruitvale BART station in Oakland, CA, Friday, January 31, 2014. Photo: Michael Short, Special To The Chronicle Photo: Michael Short, Special To The Chronicle Image 1 of / 1 Caption Close BART rider with measles potentially exposed thousands 1 / 1 Back to Gallery

Public health officials issued a warning Thursday that thousands of Bay Area residents were potentially exposed to measles last week when a UC Berkeley student with the virus attended classes in Berkeley and rode on BART.

The student, a Contra Costa County resident whose name was not released, was confirmed to have the highly contagious respiratory disease on Wednesday, and was likely to have been infected while traveling abroad, said officials with Contra Costa Health Services. The student had not received a measles vaccination, officials said.

Health officials said that anyone riding on BART between Feb. 4 and Feb. 7 during the morning commute or late evening was potentially exposed to the virus. The virus, which can stay in the air for up to two hours, was probably present on trains that moved throughout the Bay Area, they said.

BART provides an average of 390,000 rides each weekday.

People who are vaccinated or have had measles are unlikely to catch measles if exposed to the virus, officials said. However, those who have not been vaccinated are at risk.

"Measles is a serious, highly contagious disease," said Dr. Janet Berreman, health officer for the city of Berkeley, in a prepared statement. "It spreads through the air when an infected person coughs or sneezes. Fortunately, the measles vaccine is highly effective in preventing infection."

Health officials urge anyone who shows symptoms such as high fever, runny nose and watery eyes to see their doctor.