Officials say neither the student nor the relatives were vaccinated against measles.
"People who aren't immunized are very likely to get measles if they are exposed to the virus," said Erika Jenssen, Communicable Disease Programs Chief with Contra Costa Health Services' Public Health Division. "This really underscores the importance of everyone getting vaccinated."
According to health officials, both of the new cases are men in their 20s and 30s.
Because they voluntarily quarantined in their homes after their family member was diagnosed, CCHS has not identified any other people exposed to measles by these cases.
Officials say the Cal student likely became infected during a recent trip to the Philippines. Some Bay Area residents were potentially exposed to measles from Feb. 4 to Feb. 7, when the student used BART prior to his diagnosis.
Health officials recommend that anyone who used BART on those days to remain vigilant for symptoms of measles through this weekend.
Measles is a dangerous, highly contagious disease that spreads when an infected person coughs or sneezes. Health officials urge anyone who has not been immunized against measles to receive the MMR vaccine, consult their health care provider, or check their health record if they are unsure about their immunization status.
Symptoms can begin one to three weeks after exposure and include high fever, runny nose, coughing and watery, red eyes. A rash develops on the face and neck two or three days after the fever begins, and it 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.
Visit cchealth.org/measles for more information about the disease.