I’m getting a cold today and I’m not very happy about it. With that whininess out of the way, I ask the question in the subject line above. I haven’t seen my sister for a few weeks, so went to her place for dinner tonight. She also had a cold. If we had different strains or different virii altogether, could we each catch each others and then have two colds?
Would that be anything like double-pneumonia? 
Absolutely.
However, odds are that you both have the same strain, so don’t worry about it. Strains (which are different viruses, often a mutation of the strain that went around six months ago) tend to run together geographically and temporally.
Unless you have a weakened immune system, then you should have avoided you sister, JIC.
Peace.
I’m not a doctor, but I play one on this forum.
You could be double-infected, but the two strains would probably not infect the same host cell. IIRC, once a virus infects a host cell it prevents other viruses from entering that specific cell.
No, common colds are caused by the same strain of virus.
Flus, however, is a different story.
Buzz. Eww. Sorry, that is not a correct answer, but thanks for playing. You’ll receive our home version of the Straight Dope Game and a case of Turtle Wax.
From The Center for Disease Control
The biggest clue that the common cold is not caused by one particular strain of virus is that you catch colds many times in your life. If it was just one strain of virus, you’d develop an immunity to it the first time and would never catch it again.
When it comes to viruses like the cold you have two choices: develop an antibody and beat it, or, die. Each time you beat a cold, you develop an immunity to that strain (although, you can be reinfected and feel a little bit bad for a day or two as your body readily slaps down the reinfection). And so, if you get a new, full blown cold, then you can be sure it’s a different strain of the cold virus than the ones you’ve had before.
Peace.
Gesundheit!
I agree with 99% of your post, but I have one minor nitpick - colds provoke an immune response in your mucus membranes, and immune memory there lasts for only a few months. You can get reinfected with the same cold virus after that time.
If only I hadn’t sold back my virology textbook, I could even back that up.
Don’t forget Strep.
The Strep virus causes strep throat, pneumonia, & infected wounds.
And it’s getting worse–
http://www.cnn.com/2003/HEALTH/03/09/super.germs.ap/index.html
Read the link, people. Trouble’s a brewin’.
I’m no scientist, but I’m about 99% certain that streptococcus is a bacteria, not a virus, Bosda. Although I support your contention that trouble’s a brewin’!
I’m pretty sure “double pneumonia” refers to having pneumonia in both lungs, as opposed to just one.