Frankfurt - Authorities at Frankfurt international airport, Germany's biggest air hub, on Monday instructed airline crews on jets coming from swine-flu-affected areas to report any sick passengers. In the capital Berlin, Health Ministry spokesman Klaus Vater said he saw no immediate threat to Germany's populace.

Pamphlets are to be distributed to travellers at German airports advising them which symptoms to watch for and precautions they could take. Information was also being distributed to German doctors.

Vater said there had already been one case in Germany where swine flu was suspected, but tests showed it was not the swine-flu virus.

In Frankfurt, Rene Gottschalk, head of the government health office covering the airport district, said income crews must report any passenger symptoms suggesting the illness. Pamphlets for passengers were being printed.

The health office said every highly infectious human disease that had reached Germany in recent years had arrived via Frankfurt airport.

Airport operator Fraport said scheduled arrivals from the infected area included one Lufthansa flight from Mexico City daily and four flights from Mexican resorts weekly operated by Condor.