The nurse, Teresa Romero, helped treat two elderly Spanish missionaries who died after returning from west Africa with Ebola.
The 44-year-old tested positive for the disease on Monday, making her the first person known to have caught Ebola outside of Africa.
Romero went on leave after the second of her Ebola patients died on September 25 at Madrid's La Paz-Carlos III hospital, which Spain has designated to handle Ebola cases.
Five women and two men were admitted to the hospital for monitoring late yesterday as a precaution, the hospital said in a statement.
They included three nurses and two hairdressers who had contact with Romero while she was on leave from her job.
Meanwhile one person who had previously been under observation at the hospital has been discharged.
In total there are now 14 people isolated at the hospital including Romero who is the only person confirmed to have the disease.
