Okay then, May I add a few things? Some of these statements are accurate however, we must note that for the most part we are for the most part healthy. With that said Our immune systems is able to battle off these foreign invaders in our tanks, nonetheless, if someone with an immune inefficiency should have a cut on their hand, arm, or finger their white blood cells or macrophages would be unable to eat away the bacteria that entered their blood stream. Keep in mind too that if even if one of you are already infected with even the common flu, respiratory infection, or god forbid MRSA, your chances of fighting off this foreign bacteria or any other bacteria is lessened by 37%. Even worse if your taking an antibiotic, which we all know does not discriminate from good or bad the body would have to work over time in ridding off the koodie bug.
Also, most living organisms form antibodies to ward off any attachment to the hemoglobin which would in some cases and pending on the bacteria and where it hibernates, mostly in the lungs and the stomach, would only become active when the immune system has been compromised.
With that said (yawn), we keep our tanks clean, for the most part, and with the streptococcal bacteria on our skin protecting us already, chances are slim unless getting severely injected by some kind of worm is possible but slim.
oh.... and my vote is to terminate the rat and eat the squirrel...... no wait..... send it to meowser's kitty!! Lol 
(the bacteria guy)