Q. If I have a cold and drink out of a water bottle, how long can the cold germs survive to infect someone else?

A."The risk is quite low," said Dr. Jonathan Jacobs, an infectious diseases specialist who is a professor of clinical medicine at the Weill Cornell Medical College in New York.

"That is not the way colds are transmitted," Dr. Jacobs continued.

There are 200 or so different viruses that cause colds, he explained, and the major way these viruses are passed on is through contact with nasal secretions, as opposed to saliva.

"There is probably not very much virus present in saliva," Dr. Jacobs said, "and with one exception, the rare adenovirus, there is no cold virus that can go through the gastrointestinal tract and infect somebody."