They may have beat analyst expectations last week, but Visa Inc. and MasterCard Inc. aren´t quite in hog heaven.

Swine flu is the latest potential headache for both network companies, which are already facing a recession-driven slowdown in payments volumes.

The virus officially known as H1N1 has led some governments and health officials to discourage consumers from boarding airplanes or traveling to places like Mexico, where cases of the flu were first reported. A slowdown in international travel means that fewer people will use their cards abroad, which cuts into the networks´ lucrative "cross-border" transactions.

News of the swine flu outbreak was only a few days old when Visa and MasterCard reported their quarterly results last week. But investors, having learned from the SARS outbreak of 2003, already were looking for the potential impact on future earnings.

"Of course this is something that is unfolding. But as we look at it and we look at SARS, this would not cause us to back off of the guidance that we just gave you," Visa chief executive Joseph Saunders said in response to an analyst question, during a conference call Wednesday to discuss fiscal second-quarter earnings. "We would still be looking for high single digit growth, revenue growth for the year. Obviously, if something happens it might be a little less than if it doesn't, but we're talking the same range."

MasterCard, which reported its first-quarter earnings two days later, had time to insert a flu reference into CEO Robert W. Selander´s script.

"Clearly it is too early to estimate what impact the current flu crisis could have on cross-border travel," he told investors on a Friday conference call during prepared remarks. "Going back to early 2003, there was an impact on our Asia Pacific business from SARS for a period of about six to eight weeks. However, SARS had no material impact on MasterCard's overall financials."

But it´s not too early to start preparing for the potential flu fallout, said Sanjay Sakhrani, an analyst who covers both companies for KBW Inc.'s Keefe, Bruyette & Woods Inc.

"It´s a reasonable question," he said in an interview last week. Swine flu fears have created "downward pressure on cross-border, which is a very high revenue margin business for them."

Other companies involved with international payments transactions have already raised the alarm. On Thursday, the automated teller machine operator Cardtronics Inc. said that the flu outbreak will drive down transaction volumes on its almost 2,100 machines in Mexico.

"We expect to experience a slowdown in transactions, especially in the tourist areas," Mike Clinard, the president of Cardtronics´ global services unit, said during a conference call.

But at Visa, Saunders found a silver lining in the outbreak´s timing. As he told investors, the recession hasn´t left much cross-border business for the swine flu to hurt.

"A considerable number of people, as we have continued to remind everybody in our quarterly reports, have already stopped traveling. Yet you don't have the same base of leisure travel that is going on today, as there was when SARS occurred. They didn't need the flu epidemic to stay off of airplanes," he said. "Our cross border volume, I keep saying, has gone down."