BOSTON - Swine flu may have scared people straight, or maybe they're finally listening to their mothers. Whatever the reason, Americans are washing their hands more often, suggests the latest check by researchers who spy on people using public restrooms.

Checks in four big cities last month found 85 per cent of public restroom users washing their hands, up from 77 per cent in 2007. It's the best rate since these periodic surveys began in 1996.

One thing hasn't changed: Men are still dirtier. About 23 per cent of men failed to wash versus seven per cent of women.

"Those little 20 seconds with friction, water and soap" are one of the best things people can do to keep from getting sick, said microbiologist Judy Daly of Primary Children's Medical Center in Salt Lake City.

She led the project for the American Society for Microbiology and the American Cleaning Institute, formerly known as the Soap and Detergent Association. Results were given Monday at the microbiology group's conference in Boston.

Researchers from Harris Interactive combed their hair and pretended to put on makeup while watching more than 6,000 adults using restrooms at Turner Field ballpark in Atlanta, the Museum of Science and Industry and Shedd Aquarium in Chicago, Pennsylvania Station and Grand Central Terminal in New York City and the Ferry Terminal Farmers Market in San Francisco.

Best: the Chicago science museum, where 93 per cent washed up. Worst: the two train stations in New York, where only about 80 per cent washed. Men were at their worst at Turner Field, where only 65 per cent washed.

Researchers also did phone surveys of more than 1,000 adults around the country in August. The results suggest that people are kidding themselves or fibbing about their true habits -- 96 per cent said they always wash after using a public restroom.

Also, 89 per cent said they always wash after using the bathroom at home, 39 per cent said they always did after coughing or sneezing, and 27 per cent, after handling money. The biggest gain was how many said they always wash after changing a diaper: 82 per cent, up from 73 per cent in 2007.