“Flu's or influenza as it's scientifically called is what we all get from time to time, weeeellll not me exactly.. but a lot of people do.”

“It’s because you’re just that special, right?” Donna concluded.

“But ever wondered why?” The Doctor kept going completely ignoring the many stares of patients yet to be treated.

“…Well I guess you could say lack of vitamins or something like that.”

“Yea, I guess you could!” shouted yet another disgruntled patient yet to be treated.

“…But that is not always true… In fact, I’m certain that Flu is not even human based, apart from the whole snot thing that is completely human... Weird creatures you are.”

“you may want to hurry this speech up a bit Doctor the crowds not looking to happy”, Jack noted the still not caring Doctor.  

“But the fact is Flu is much like bit-torrent each time you get it the more data is slowly transferred, ingenious really no-one suspects the cold! Oh what’s that fever? Runny nose? Take an aspirin it'll pass! Well the physical signs do but the data is permanently stored waiting for more data or as you would say another Flu to attack your immune system!” The Doctor grinned quite happy with his comparison.  


“How is that possible you say? Who would want to do that?”


“First it is very possible; second anyone who wants to enslave the human race! And that is a lot.”


“...Well don't look so shocked! The whole Flu thing wasn't ever healthy for you in the first place!... Unless instead of stamps you collect various types of Flu's... actually let’s not go there.”


“The point is, every Flu you have caught has been different, none the same!” that’s all the different bits of data and who wants to download the same thing twice?”


“The matter of the fact is the download is almost complete.”