Does anyone know if it’s possible (and if so, common) to contract more than one cold at a time? I am currently suffering from a bad cold, as are my wife and two daughters. In the worst possible case, could we each be suffering from FOUR DIFFERENT COLDS? :eek: Or is there something about cold viruses (viri?) that makes them tend to be one-at-a-time affairs?
-P
Either no one knows, or no one cares.
Either way, this will be my one and only bump of this question. 
IIRC, there are dozens of different viruses that cause “cold-like symptoms,” and each of those has hundreds of mutational forms that make them just different enough that your immune system has to learn how to fight them all over again. That’s why scientists can’t invent one cure for the common cold - it’s not common!
So, yeah, it’s entirely possible that all 4 of you have different viruses, or at least different strains of the same virus. Even if everyone in your family was infected with the same strain of the same virus, exactly which symptoms you have depends on what your immune system is doing at the time. So, just based on the symptoms, it would look like you all had different infections.
In dealing with animal medicine, we tend to see single viral infections. Sometimes the immune system is overwhelmed enough that other pathogens set up shop too (usually bacteria that don’t normally cause a problem but are taking advantage). However, those animals are generally SICK. In theory, a virus that attacks the same cells that are currently under assalt from another virus won’t set up an infection well. The cells that it prefers are already being destroyed by the first virus.