Pharmacist admitted to hospital on Indian Ocean island with a moderate fever had recently carried out humanitarian work in Ebola-hit Guinea.
The French President is the first Western leader to visit Guinea, where more than 1,200 have died from the disease since the March outbreak.
The patient, who contracted Ebola while working to combat the epidemic in Sierra Leone, has been placed in isolation in a military hospital.
Passengers arriving on flights from Guinea, which Air France crews urge should be suspended, are being tested for fever by hand-held laser kits.
Charles de Gaulle airport will begin on Saturday monitoring temperatures of passengers arriving from Guinea to detect carriers of the disease.
Experts predict 75 percent chance virus could be imported to France by October 24 and 50 percent chance it could hit Britain by then.
Volunteer nurse who caught the disease while working for a charity in Liberia made a full recovery after experimental treatment.
The unidentified woman, infected by the virus while serving Doctors Without Borders in Liberia, is being treated in a Paris military hospital.
The woman, on assignment with the Doctors Without Borders association in the capital Monrovia, is to be returned to France for treatment.
Development secretary Annick Girardin is in Guinean capital Conakry to visit Ebola units and discuss France's role in halting epidemic.
Unions say management has promised no action will be taken against pilots or cabin crew not wishing to fly to affected regions.
The airline said it has temporarily halted its three weekly flights to Freetown at the request of the French government.
Foreign ministry says trips to four countries hit by Ebola fever outbreak - Liberia, Guinea, Sierra Leone and Nigeria - should be put on hold.