SAN FRANCISCO (Reuters) - Commuters on San Francisco’s Bay Area Rapid Transit system may have been exposed to measles last week after an East Bay resident with the disease rode a BART train to and from work in the city for three days while infectious, public health officials said on Wednesday.
The infected BART rider marks the first case of measles documented by Contra Costa County health officials during an outbreak of the virus that has infected more than 100 people in California since December.
Fewer than 10 of those cases have been diagnosed in the San Francisco Bay area. Most have occurred in Southern California, many linked to exposure to an infected person who visited the Disneyland resort in late December.
Contra County health officials sought to reassure the public that the infected BART train rider did not pose a high risk of contagion to other passengers.
“Although the risk of contracting measles by being exposed on BART is low, Bay Area residents should be aware of the situation,” the county public health department said in a statement.
The infected person traveled between the Lafayette station in the East Bay and the Montgomery station in San Francisco during the morning and evening rush-hour commutes on Wednesday, Thursday and Friday of last week.
That ride is 35 minutes long, but health officials said that the highly infectious, airborne virus could have remained in the air for up to two hours. Because BART cars circulate throughout the Bay area, anyone who used the transit system during that time could have potentially been exposed
“Even if the rider got off BART at Montgomery station, commuters for the next hour or two could have been exposed,” said Erika Jenssen, Contra Costa County’s communicable disease programs chief.
Nearly 400,000 ride BART each weekday on average, but the number of passengers who rode the same line or the same train cars during those hours was not immediately known.
Public health officials were tracing the movements of the person, who is recovering and not hospitalized, and notifying others known to have had close contact, the statement said. It said the person’s employer is cooperating with the inquiry to ensure the safety of any co-workers who may have been exposed.
The infected person also spent time at the E&O Kitchen and Bar in San Francisco on Wednesday evening, potentially exposing others who were in the restaurant between 5:30 p.m. and 7 p.m., health officials said.
Individuals who are vaccinated or have had measles before are extremely unlikely to catch the disease, even if they had contact with a contagious person. However, those who were not previously vaccinated are at high risk if exposed.
Additional reporting by Noel Randewich in San Francisco; Writing by Steve Gorman; Editing by Cynthia Johnston, Mohammad Zargham and Cynthia Osterman