PARIS - The threat of a swine flu pandemic kept global businesses and investors on edge today, disrupting travel plans and sending stock markets down on fears the outbreak could worsen and cause more economic misery.

Days after news of the deadly virus outbreak in Mexico, stocks of companies in the travel and tourism industry were being hammered on fears that worried travelers would stay home.

Across Asia, tour groups abandoned more holiday jaunts to the country amid a series of government warnings. Airports from Indonesia to Australia tightened their screening of travelers.

In Moscow, the U.S. Embassy issued a statement saying there was "no basis" for Russia's decision to bar pork imports from three U.S. states, saying the disease was not spread through meat products and hoping normal trade would soon resume.

Much of the fallout hit financial markets jittery about the future, as opposed to the real economy. Shares in Europe's largest airline Air France-KLM continued the sharp drop begun Monday, falling an additional 2.85 percent today. Shares in European hotel giant Accor SA, which operates 9 Sofitel and nearly 1,000 Motel 6 hotels in the United States, slid 4.35 percent.

The disease, while still largely corralled in North America, has spread rapidly in recent days with the World Health Organization raising its global alert level and moving closer to declaring a flu pandemic as infections cropped up in Europe. Asia's first cases were confirmed in New Zealand; another case emerged in Israel. The virus is suspected in about 150 deaths, all in Mexico.

With the world economy already seen shrinking 1.3 percent this year by the International Monetary Fund, swine flu could add more stress by further eroding trade, consumer spending and investment, snuffing out what many say are the glimmers of a recovery.

"This certainly could exacerbate the recession," said Sherman Chan, an economist with Moody's in Australia. "The next couple weeks will be crucial. If this persist, it could become a more serious concern and really cripple the economy."

For the U.S. economy, any turnaround could be delayed well into 2010. In a worst-case scenario, the U.S. economy would shrink by an extra 0.3 percent this year, on top of a predicted 3.5 percent decline.