Oil prices fell on Tuesday on concerns the swine flu outbreak could further depress demand.
US crude oil settled 22 cents lower at $US49.92 per barrel. London Brent fell 33 cents to $US49.99 per barrel.
Swine flu has killed 149 people in Mexico and spread to other countries.
The flu has hit airline stocks on expectations travel will be curtailed. Analysts warn that jet fuel demand may slump, citing a drop in consumption that corresponded to the SARS epidemic in 2003.
Oil demand is already down due to the global economic crisis, sending prices well below a record $US147.27 per barrel reached on 11 July last year.
Since September, members of OPEC have agreed to lower their output by 4.2 million barrels per day to prop up prices.