Health authorities in southern Germany have appealed for all travellers who may have been in contact with a student suffering from Lassa fever to come forward.

The student contracted the dangerous disease during a trip to West Africa and returned to Germany five days ago on a flight from Ivory Coast by way of Lisbon.

Doctors in Wuerzburg in Bavaria where she is being treated said her condition was critical.

The authorities said the chances that passengers on the same flight had caught the disease from her were very minimal but the risk could not be ruled out altogether. Lassa fever -- a viral infection which causes severe and often fatal internal bleeding -- was named after the Nigerian town where it first appeared thirty years ago.

From the newsroom of the BBC World Service