SAN FRANCISCO » Officials in Northern California on Wednesday warned Bay Area Rapid Transit commuters that they may have been exposed to measles after an infected LinkedIn employee used the trains.

Contra Costa County public health officials say someone diagnosed with the disease rode BART trains between Lafayette and San Francisco during the morning and evening commutes Feb. 4 through Feb. 6.

Officials said Wednesday that the patient also dined at E&O Kitchen and Bar on Feb. 4.

The state Department of Public Health said it does not know how many San Francisco Bay Area residents have measles vaccines. The number of parents declining to vaccinate their children has risen in the region — and the country — in recent years, though the majority is vaccinated.

LinkedIn said in a statement it was informed on Tuesday an employee based in its San Francisco office was diagnosed with measles. The employee lives in Contra Costa County.

Health officials said Wednesday that those without vaccinations who came into contact with the BART commuter are a "high risk" of coming down with measles. People displaying symptoms are urged to seek medical attention immediately. Symptoms include high fever, runny noses, coughing and watery red eyes and can begin from one to three weeks after exposure. An infected person is contagious for several days before and after the rash appears.

Health officials say the risk of vaccinated commuters contracting measles is "highly unlikely." People born before 1957 are considered immune.

Meanwhile, health officials in Nevada warned Wednesday that anyone who ate last week at a top-name Las Vegas Strip restaurant should review their immunization status and contact their health care provider if they are not fully immunized against measles and have not already had the disease.

Tests confirmed this week that a child and an adult have measles, bringing to four the number of cases reported since the beginning of the year in and around Las Vegas, the Southern Nevada Health District said. The adult, who wasn’t fully vaccinated, works at Emeril’s New Orleans Fish House at the MGM Grand Hotel & Casino, the health district said.

More than 100 people in California and others in several states and Mexico have been infected with measles since an outbreak traced to Disneyland was first reported in December.

It’s not known how the commuter contracted the disease. Health officials urge vaccination.

"The measles vaccine is very effective and is a standard part of pediatric primary care," said Dr. Tomas Aragon, San Francisco Health Officer. "While we are concerned about the current outbreak in California and its potential to spread, we cannot emphasize enough that the solution is simple and available: be vaccinated."