Stocks in the United States fell on Monday on concerns a new strain of flu could dampen optimism about the economy.
The three major US indexes slid in choppy trade as governments around the world moved to contain the spread of a swine flu outbreak that has killed up to 149 people in Mexico and spread to the United States, Canada and Europe.
Airlines were hit: UAL Corp, the parent of United Airlines, fell 14.3% to $US5.50 and Continental Airlines Inc lost 16.4% to $US11.08.
However, stocks of drugmakers rose: Gilead Sciences climbed 3.8% to $US47.53 on Nasdaq.
Shares in General Motors surged 20% to $US2.04 after the automaker announced a restructuring that investors hope will keep the company alive while it tries to secure government funding.
The Dow Jones industrial average fell 51.29 points, or 0.64%, to 8,025.00.
Standard & Poor's 500 Index dropped 8.72 points, or 1.01%, to 857.51. The Nasdaq Composite Index shed 14.88 points, or 0.88%, to 1,679.41.
The Dow average is up 22.6% since 9 March, but remains down 8.6% for the year.
Trading was moderate on the New York Stock Exchange, with about 1.40 billion shares changing hands - below last year's estimated daily average of 1.49 billion.
About 2.23 billion shares were traded on the Nasdaq - below last year's daily average of 2.28 billion.