Good story, great potential
It was a nice flash and a great idea for a storyline.
The things I didnt liked in this flash was the text log part (you could just show they talking on the monitor or some flashbacks showing what they-re saying) and the infection part (that shape animation sucked badly). This 2 things take most of the animation. The rest was very nice (i loved the landing and crash part). The sound was just a loop and no sound effect, but at least it has to do with the animation.
Although it isnt very original, the story was great. You just should spend more than 1 day developing it :P.
But i dont agree that the chances are of we get infected by an alien virus.
1st, the virus wasnt developed in our ecosystem, so the chances that its incompatiple with our biology and our environment is too great.
2nd, a virus must have a balance of time beetween infection and death of host, so it can multiply more effectively. A virus that kill very fast generally dont spread too fast. Unless its transmission is highly effective (by air). If thats the case the virus must be adapted to live in our air.
Well, it was just my thoughts and it didn't influenced in my score.