Q. Can I get two colds at once?

A. Yes, you can. The phenomenon is known medically as coinfection and occurs when two germs, in this case viruses, cause infections at the same time.

More than 100 viruses can cause the common cold, so it’s not unusual to be exposed to two at once. And, since one virus doesn’t typically confer immunity against the other, it’s not unusual to be infected by two viruses at once.

The best data about coinfection come from studies of more serious viruses, such as H.I.V. and hepatitis. These studies show that coinfection can worsen, ameliorate or have no impact on the course of an illness. The outcome depends on the viruses involved.

With H.I.V., coinfection with the two main types, H.I.V.-1 and H.I.V.-2, is actually beneficial. It slows the progression of the disease. Coinfection with H.I.V. and hepatitis C virus, on the other hand, worsens the outcome.