There are two basic shapes of bacteria that you'll see quite often. There is bacilli which is rod shaped and cocci which is circular shaped. Clusters of cocci together form three common forms. These forms are diplococci, staphylococci, and streptococci. But, there are also the forms of spirillum(Corkscrew) and vibro(C or comma) which appear along side the cocci and bacilli. Unlike their viral cousins, bacteria produce far faster and are far easier to cure in most cases than viruses. Influenza is a virus which comes in three forms. The most common form in Influenza A and are classified by using H a number and N then a number. It is the fast growing virus and perhaps one of the most dangerous if left untreated in the winter time. Influenza can cause progression into bronchitis by weakening the immune system. If the bronchitis goes untreated then pneumonia can form as well. Pneumonia causes approximately four million deaths a year so in the apocalypse catching such a disease without the possibility of treatment by anti-viral or antibiotics means a near certain chance of death.

So how about that Sven?

Edit: Also, if you know Legionnaires disease than you might be surprised about this. Legionnaires disease was discovered at a meeting for people of some Legion or another here in America. I don't quite remember who they were but after their dinner, many people started to express symptoms of Legionnaires. After some epidemiologist was sent into study, it was discovered that the cause was from the food. Primarily a salad was the culprit. The lettuce which had been used had been watered by a singular pipe at a farm containing a bacteria. The plant which produced the lettuce had not known about the bacteria which managed to mostly survive their cleaning system. What did survive, was capable of reproduction inside the bags. So, when the dinner was held the bacteria was primed and ready to infect a new host and thus travel to humans. 

Edit2: Actually to clear the above up I must say that Legionnaires is technically caused by bacteria in aerosolized water. So technically it is true as the above.