My 3-year-old has had chickenpox for about 2-3 days, but a close friend has just had a baby and I want to go and help. Is it possible that I am infectious, despite not having the illness? I had it as a child, so (hopefully) can't actually get it myself. Thanks!
You may be carrying the virus
You may not show any symptoms, but if you've had chicken pox already, you most likely have the virus in your system even without being exposed to the virus recently. This virus, the varicella-zoster virus, remains dormant in your system, and can become active later in life, causing shingles.
While shingles can't be transmitted from person to person, an active outbreak of shingles can infect someone with chicken pox, if they've never had it, or if they have a weakened immune system (such as a newborn infant).
Note that the transmission methods for chicken pox and shingles are different.
Chicken pox can be contagious before symptoms even appear, and spreads through contact with bodily fluids, or from airborne virus spread from someone who is infected and coughing and sneezing.
However, just because you've had chicken pox as a child doesn't mean that the only way you could possibly transmit the virus is through direct contact with a shingles rash. While most people who have had chicken pox in the past have a lifelong immunity to it, rarely some people do get chicken pox a second time. If you are one of those rare cases who get chicken pox a second time, you could be contagious without showing any symptoms (yet).
Therefore, if you know you've been exposed to the chicken pox, even if you've already had it, do not go. It simply is not worth the risk.
While frustrating that you might have to stay away and can't see the little tiny baby, it'd be terrible if you made them all ill.
I would suggest that you call the close friend and tell them.
If you are still worried, consult your family doctor or medical helpline.
Some information on breast feeding and chicken pox: http://www.netwellness.org/question.cfm/8650.htm
Once you've had chicken pox, it never actually leaves your body and can re-emerge years later to cause shingles. The virus that causes both chicken pox and shingles is related to the herpes virus, and like herpes it lies dormant in your nerve cells between outbreaks:
So simply having it as a child in no way means that you can't be a carrier of the active virus. Being exposed to the active virus typically won't cause an outbreak in an already-infected adult (because your immune system is quick to respond and will drive the newly acquired active virus into a dormant state) but it does mean that you can be infectious to others even though you show no symptoms yourself.
So regardless of whether you've had chickenpox before or not, if you are recently exposed to the virus from somebody with an active infection, you should consider yourself contagious and should avoid exposing others.