The inmate saw a doctor Tuesday morning with flu-like symptoms, and the doctor, who said it was possibly mumps, collected a specimen that was sent to state health officials to be tested, San Mateo County Health System spokeswoman Robyn Thaw said.
"We are not reporting this as an outbreak or even as a confirmed case of mumps at this time," Thaw said.
Some third-floor inmates at the Maguire Correctional Facility have been quarantined until the case is confirmed, sheriff's Lt. Larry Schumaker said.
Thaw said the results could be returned by the state as early as the end of day today.
The affected inmates are restricted from using common areas or leaving the facility to attend court. Visitation is also restricted, with family visits canceled for those inmates.
San Mateo County Chief Deputy District Attorney Steve Wagstaffe said the mumps scare has affected court proceedings in seven felony cases -- one jury trial and six pretrial conferences.
The inmate involved in the jury trial was cleared to appear in court, but the six pretrial conferences will need to be rescheduled, Wagstaffe said.