DEAR DOCTOR K:

A lot of my female friends seem overly worried about sitting on public toilet seats. They think doing so could give them diseases like herpes, gonorrhea, syphilis and HIV. I'm more worried about the mess left by those who "hover" over the seat unnecessarily. Who's right?

DEAR READER:

It's not completely irrational to worry about dirty public toilet seats. Any contaminated surface can spread infectious disease. However, the real risk of catching a disease from a clean toilet seat is almost nonexistent.

The enormous efforts people make to avoid touching public toilets aren't really necessary. Many public toilets have a dispenser with paper to cover the toilet seat. When that is not present, many people cover the toilet seat with toilet paper. If the toilet seat is visibly clean, those precautions are of little value.

Nevertheless, many of us were taught as kids to cover the toilet seat with paper in a public bathroom. I was, and I feel a little more comfortable when I do it. Like most human beings, my brain sometimes speaks to me in two voices. The emotional voice sometimes wins out over the rational voice.

In particular, you really don't have to worry about catching the diseases you mention -- herpes, gonorrhea, syphilis and HIV. These diseases are spread by unprotected, skin-to-skin sexual contact. It's very unlikely that they could be transmitted via a toilet seat. That's because the viruses or bacteria that cause them die very quickly outside the body.

HIV can also be spread through blood transfusions with infected blood products or a needle stick from a contaminated needle. Toilet seats are not on the list of likely modes of transmission.

Public restrooms, like all public places, do present risks from infectious diseases. But those risks are not from toilet seats. Surfaces you touch with your hands -- the flush handle on the toilet, the water faucet handle on the sink, the doorknob on entering or exiting the restroom -- can be contaminated with germs.

Your hands are very hospitable to bacteria, such as staph germs and E. coli. Your hands can pick up the flu virus, too. And then it's really easy for you to spread those germs from your hands to your nose and mouth. From there, they get inside your body.

So always wash and dry your hands thoroughly before leaving a public restroom. After I've washed my hands, if I still need to grab a door handle to leave the restroom, I will then use an antibacterial hand gel.

Finally, some viruses and bacteria are spread by sneezing and coughing. Especially during flu season, try to not get too close to people who are coughing and sneezing. They pose a greater threat to you than a toilet seat.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: www.AskDoctorK.com.)

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