Carnival Corp. (CCL) said fiscal second-quarter earnings will be cut by about 5 cents a share from having to change cruise routes in the wake of the A/H1N1 influenza virus centered in Mexico, an impact perhaps less severe than some investors expected.

In addition to the 5-cent profit reduction from the changes through June 15, Carnival said Monday up to an additional nickel a share could be cut from full-year earnings results because of further impact from the illness.

A Royal Caribbean Cruises Ltd. (RCL) spokeswoman said that at this time, it does not plan on making a similar announcement about any impact the A/H1N1 influenza virus may have on earnings.

The world's largest cruise ship operator by market share, Carnival rose 5% recently to $26.31. Competitor Royal Caribbean's shares also saw a lift, adding nearly 10% to $15.76.

"When the swine-flu story broke and the cruise lines modified their itineraries, it had the potential to be a significant risk to demand going forward," Zacks Investment Research analyst Sean P. Smith said. "As more has been discovered about the nature of the virus and its severity, however, those risks to short- and long-term demand seem to have diminished."

The concern had been that the outbreak could reduce the number of passengers or force the cruise companies to lower ticket prices further. Either way, that could hurt passenger yields, a measure of ticket prices and onboard spending.

Just after A/H1N1 concerns came to light in late April, UBS estimated that it would take a 20% reduction in full-year passenger yields for the small percentage of Mexican itineraries affected from each operator to impact company-wide yields on an annual basis by about 1%.

The firm estimated that, for Carnival, each 1% change in net yields represented about 15 cents to 2009 earnings per share, while for Royal Caribbean, each 1% change in net yields represented about 24 cents to 2009 earnings per share.

Both Carnival and Royal Caribbean steered passengers away from Mexican ports after the U.S. Centers for Disease Control and Prevention recommended against non-essential travel to Mexico.

That recommendation was lifted Friday, but Carnival said Monday that some of its routes won't return to their original form until mid-June.

Carnival said 27 ships had to change route from three of its brands. The company said it will continue to monitor booking trends and provide an updated guidance on its second-quarter earnings call, scheduled for next month.

Royal Caribbean decided late Friday to resume port calls to Cozumel, beginning with sailings that depart on or after May 24, a spokeswoman said. Its Mariner of the Seas will continue its modified Pacific Northwest itinerary, up to and including its June 14 sailing.

In an April 2 financial filing, Carnival projected fiscal second-quarter earnings to be in the range of 29 cents to 31 cents a share and lowered its full- year view to $2.04 to $2.24 from its March forecast of $2.10 to $2.30. The quarter concludes at the end of this month.

Royal Caribbean expects its second-quarter earnings per share to be flat to a loss of 5 cents. It projects full-year earnings to be around $1.35.

-By Kelly Nolan; Dow Jones Newswires; 201-938-4049; kelly.nolan@dowjones.com

(Kevin Kingsbury contributed to this report.)