Can colds get passed back and forth?

About two months ago, both my six-month-old son and I got a long-lasting cold. Then a week ago, I got sick with another tenacious cold. Now he is showing symptoms too, including an intermittent low-grade fever. The nurse practitioner said, "Maybe you're passing it back and forth." Is that possible or is it just that our immune systems are weakened and vulnerable to other germs?


Robert Steele

Robert W. Steele, MD, is a board certified pediatrician at St. John's Regional Health Center in Springfield, MO. He graduated from medical... Read more

The typical sequence of events that occurs when one gets a viral illness is as follows:

First, the virus makes its way into the body. Most cold viruses are transmitted hand-to-mouth. The virus attaches itself to the cells within the nose and mouth where it begins to multiply and get distributed into cells within the bloodstream. During this time, the virus is multiplying greatly without causing a whole lot of symptoms. This is what is referred to as the incubation period. At some point, the virus has multiplied so much and killed so many cells that symptoms develop. If the destroyed cells reside in the nose, it runs. If there are a lot of cells killed in the throat, it gets sore. If it gets to the intestinal cells, diarrhea ensues, etc. Meanwhile, the body starts to realize there is a foreign invader and begins making what are called antibodies. These antibodies are proteins that can attach to the virus and the cells that are infected so that they may be destroyed. This "war" causes side effects like fever and body aches. Eventually, the antibodies significantly outnumber the viruses and the body successfully eliminates the virus.

But what happens to the antibodies once the virus is gone? Well, they slowly decrease in number but it takes weeks to months to get to a level where infection with that exact virus could occur again. And the body sets up a system to allow for very rapid production of these same antibodies if that same virus is encountered again. This makes reinfection possible but highly unlikely. This is most obviously seen with chicken pox. After the infection, the body can crank up antibodies very quickly to prevent reinfection. That is why most people only get chicken pox once in a lifetime.

Your question is a great one, and your suspicions are correct. Passing a cold "back and forth" within a family is generally quite unusual. Most of the time, this phenomenon can be explained by the fact that another virus has unfortunately invaded the household shortly after the last one.

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