That's the interesting thing that we've seen hints of. It's pure speculation, but it looks like it might be deadly only when you get the double-whammy that you're describing. If so, that would be great news.
One of the factors that could enter into this is - that combo aspect - is that it is well-known that the human body carries around with a host or number of different, active contagions - kept in check by our immune systems ... get chilled, run down, and get 'over-taken' by those contagion *already* existing in one's system ... when something *new* comes along, of course, the body develops (attempts to develop anyway) the counter measures for the 'new' contagion while the patient goes into a 'fever' state ...