Three cases of C diff are being treated in isolation and oncology ward 2c at Raigmore Hospital in Inverness closed.NHS Highland said the risk to healthy patients, visitors and staff were minimal.
In February, ward 6c was closed after a patient contracted the potentially lethal bug. In January, ten patients at the hospital were affected by C diff forcing the closure of ward 4c.
The health board said cleaning would be increased to prevent further cases. Patients on strong antibiotics are particularly susceptible to infection.