Men are much worse about it than women. Museum visitors do it more often than sports fans. And in general, we're all doing it less and less these days.
The practice of hand washing - at least in public restrooms - is on the decline and no one is sure why.
While Americans profess to wash their hands when questioned in surveys, they do it much less frequently in reality, according to observations of 6,000 people using public restrooms at six prominent venues in Atlanta, Chicago, New York and San Francisco.
Hand washing is a key tool in fending off germs, experts say. The U.S. Centers for Disease Control and Prevention considers it the single most effective step in preventing the spread of ailments ranging from colds and flu to a host of nasty gastrointestinal bugs.
"It's the number one public health tool around today," said Kellogg J. Schwab, an associate professor of environmental health at the Johns Hopkins Bloomberg School of Public Health.
Noroviruses alone, which cause nasty bouts of nausea, vomiting and stomach distress, infect 23 million people in the United States each year, and much of their damage could be prevented by hand washing.
But phone surveys and real-world observations conducted by the American Society for Microbiology and the Soap and Detergent Association show that we aren't all listening.
In a telephone poll of 1,001 people, about 92 percent professed to wash their hands whenever they used a public restroom. But when observers discreetly recorded the behavior of 6,076 men and women in high-volume washrooms around the country, only 77 percent actually did it. And that's down from 83 percent who washed up in 2005.
"I don't think the message is getting out," said Judy Daly, a society spokeswoman who is director of microbiology lab at the Primary Children's Medical Center in Salt Lake City, Utah, and a pathology professor at the University of Utah School of Medicine.
The researchers sent observers into restrooms in New York's Grand Central Terminal and Penn Station, the San Francisco Ferry Terminal Farmers' Market, Chicago's Museum of Science and Industry and Shedd Aquarium, and Turner Field, the home of the Atlanta Braves.
Observers were instructed to appear occupied by grooming themselves - but not to wash their hands more than 10 percent of the time. They also rotated bathrooms every hour or so to avoid counting repeat users.
"If they were in there washing all the time, they might have thrown off the results," said Brian Sansoni, a spokesman for the Soap and Detergent Association - whose members would sell more soap if more Americans washed up. If someone was observed spending only five or 10 seconds just rinsing their fingers, that didn't count, Sansoni said.
Men were worse slobs than women. Eighty-eight percent of women washed their hands this year, down only two points from2005. Only 66 percent of men washed up, down from 75 percent two years ago.
The gender differences were most pronounced at Turner Field, where 95 percent of the women but only 57 percent of the men washed their hands. "The women did a beautiful job there, and the guys did a horrible job," Daly said.
A spokeswoman for the Braves declined to comment on the results. But those familiar with the survey said the behavior patterns would probably occur at any sporting event.
"I think no matter where you go, guys have a little more work to do," said Sansoni.
Men performed best at Chicago's Shedd Aquarium, where 81 percent of men and women washed their hands.
No one is sure why men, overall, are less likely to wash up. "It's a bit of a head-scratcher because it's so easy to do," Sansoni said.
The trend surprised some experts. "You would think the hand washing would be going up, with all the heightened awareness about flu and pandemics," said Polly Ristaino, associate director of hospital epidemiology and infection control at Johns Hopkins Hospital.
In October, the hospital will launch an in-house campaign featuring posters reminding staff of the importance of hand washing.
Why is it so critical? If one person coughs or sneezes on his hands and touches a doorknob or other surface, the next person can pick up whatever bacteria and virus might be left there, Ristaino and others said.
If that person puts a hand to his mouth or eyes, he can be infected with a cold, flu or gastrointestinal infection.
"Anything you come into contact with - pens, doorknobs, countertops. They all will hold it," said Utah's Daly.
Viruses can be particularly hardy - surviving for weeks on doorknobs, countertops, telephones, light switches, elevator buttons and other surfaces, according to Bloomberg's Schwab.
And spreading infection doesn't require a sneeze or cough. Germs hide in a baby's diaper, a pet's fur or the cash in our wallets. The ASM recommends hand washing before we eat, as well as after we use a bathroom, sneeze, cough, or handle a dog, cat, cash or diaper.
"People wonder, 'Why is this important to me?'" Schwab said. "They don't realize that it is."
Germs such methicillin-resistant staphylococcus aureus, a hard-to-kill staph infection better known as MRSA, can live for days and even weeks in someone's nose without producing symptoms. But the host can pass it on to others unknowingly by wiping his nose and touching a table that someone else touches, experts say.
MRSA causes deadly blood infections and pneumonias. Some say the rise of such drug-resistant superbugs is one of the nation's most alarming public-health threats.
More common infections are also spread by unwashed hands. Noroviruses that sicken cruise ship passengers, for instance, can be spread when someone touches a surface contaminated with it, according to the CDC.
The CDC and the American Society for Microbiology recommend washing for at least 15 to 20 seconds, about the amount it takes to sing "Happy Birthday" twice.
Schwab said he has given that instruction to his 10-year-old daughter - but noted that she has "learned to sing 'Happy Birthday' very fast."
Health experts and others who have studied the issue say they are not surprised by the study results released yesterday.
"Not only do people not wash their hands - they say they do, but they don't," said Gayle Westmoreland, a retired telecommunications manager from Howard County who has written a book and set up a Web site urging people to stop shaking hands - precisely to avoid these infections.
"Why can't we simply do a nod?" she asked.
To view a video on proper hand-washing technique, go to: www.baltimoresun.com/germs
Proper hand washing techniques
Wet your hands with clean running water and apply soap. Use warm water if it is available.
Rub hands together to make a lather and scrub all surfaces. Continue rubbing hands for 20 seconds. Need a timer? Imagine singing "Happy Birthday" twice through to a friend.
Rinse hands well under running water.
Dry your hands using a paper towel or air dryer. If possible, use your paper towel to turn off the faucet.
If soap and water are not available, use alcohol-based gel to clean hands.
[Source: U.S. Centers for Disease Control and Prevention]
WHY YOU SHOULD WASH YOUR HANDS
Illnesses that sometimes can be prevented by hand washing:
Fever, headache, cough, sore throat, muscle ache and stomach distress.
Flu-like symptoms, but colds are usually milder and more likely to produce a runny or stuffy nose.
Sometimes called stomach flu. Symptoms usually include nausea, vomiting, diarrhea and some stomach cramping. Some victims suffer a low-grade fever, chills, headache, muscle aches and fatigue.
Respiratory syncytial virus (RSV)
A common cause of pneumonia in infants. Symptoms include fever, runny nose, cough and sometimes wheezing. Up to 2 percent require hospitalization. Most recover in eight to 15 days.
Cold and flu-like symptoms, along with possible gastroenteritis, conjunctivitis and rashes.
Diarrhea, fever and stomach cramps starting a day or two after victims are exposed to the bacterium.[Source: U.S. Centers for Disease Control and Prevention]