One of Carnival Cruise Lines’ worst fears came to pass Thursday when crew members on one of its ships were diagnosed with swine flu.

The news sent shares in the company down by about 2% to $24.23 in afternoon trading. Carnival said the Pacific Dawn had to be diverted to an Australian port.

The ship, owned by P&O Cruises but operated by Carnival, is carrying 2,000 passengers on a trip that began Monday. The ship had just returned from its prior sailing, during which several people complained of flu-like symptoms. More than 20 passengers and crew on that previous cruise have since been diagnosed with swine flu.

Already reeling from fewer bookings amid the recession, the cruise-line industry was served a double whammy by the swine-flu outbreak in April.
Both Carnival and rival Royal Caribbean Cruises banned routes to Mexico when the flu first broke.

Carnival cut its earnings outlook to reflect those itinerary changes, but said its ships would resume trips to the region by mid-June.

The company estimated its itinerary changes in the Caribbean will lower earnings by about 5 cents a share, mostly in the second quarter. For the full fiscal year, that could rise to about 10 cents.

Shares of Royal Caribbean also lost ground in Thursday’s session, falling 3% to $14.34