SAN FRANCISCO — Hotel guests leave behind more than just socks and old paperbacks: A new study found viruses on TV remotes, light switches and even hotel pens after cold sufferers checked out.

The germ testing was done before the rooms were cleaned, so it likely overstates the risks that most travelers would face. Nevertheless, it shows the potential hazards if a hotel's turnaround amounts to little more than changing the sheets and wiping out the tub.

"You sure hope the cleaning people were good," said Dr. Owen Hendley, the University of Virginia pediatrician who presented results of the study yesterday at a meeting of the American Society for Microbiology.

Besides hotel hazards, the findings point out things that people may not think to clean in their homes when someone has a cold.

"We know that viruses can survive on surfaces for a long time — more than four days," said Dr. Birgit Winther, an ear, nose and throat specialist at the university who led the study.

Its aim was to test the survival of rhinoviruses, which cause about half of all colds, especially in children.

Researchers had 15 people with lab-confirmed rhinovirus colds spend a night in individual rooms at a nearby hotel and, after they checked out, tested 10 items they said they had touched. About one-third of the objects were contaminated with rhinovirus.

"We were surprised to find so many," Winther said.

Virus was found on 7 out of 14 door handles and 6 of 14 pens. Six out of 15 light switches, TV remotes and faucets tested positive, as did 5 of 15 phones. Shower curtains, coffeemakers and alarm clocks also harbored viruses.

Surprisingly, viruses turned up on only one of the 10 toilet handles tested.

Experts did not test items like bedspreads because cloth dries out germs, making them far less likely to survive than they do on smooth or moist surfaces.

Several months later, five of the 15 participants were asked to return to the hotel and visit rooms where certain items had been deliberately contaminated with their own mucus, which had been frozen previously when they had their colds.

Because they had developed immunity to these germs, doctors could study how easily they picked them up without putting them at risk of getting sick again.

Each volunteer visited two rooms, and their hands were tested afterward for viruses. Results were positive on 60 percent of contacts in rooms where mucus had dried for at least an hour, and on 33 percent of those in rooms where mucus had dried overnight.

The study was sponsored by Reckitt-Benckiser Inc., makers of Lysol, but did not test any products. Doctors with no ties to the company designed the study to lay the groundwork for future research on germs and ways to get rid of them.

Some in the hotel industry say they have strict policies on how to disinfect rooms between guests.

"We do wipe everything down, from the remote control to the telephone," said Michelle Pike, corporate director of housekeeping for Hilton brand hotels, which has 1,900 hotels around the world. Most of them are independently operated, but the chain does have rules for disinfection, she said.

Hilton, like many hotels, has taken steps to make common items easier to clean, like encasing phone books in plastic and replacing bedspreads with duvet covers than can be washed between each guest, she said.

And if germs are lingering on surfaces in hotel rooms, "you can be damn sure it's more likely to happen at home," Hendley said.

To wipe down home surfaces, doorknobs and light switches, "standard household cleaners will be adequate," said Dr. Frederick Hayden, a University of Virginia infectious diseases specialist who had no role in this study but has consulted extensively with companies developing viral vaccines and treatments.

Dr. Stuart Levy, a Tufts University physician who heads the Alliance for Prudent Antibiotic Use, advocates lots of hand-washing and not going overboard trying to debug your home.

"How clean do you need to be? You don't go through with a blowtorch," he said.