Some bacteria can cause diseases. These are called pathogenic bacteria.
Although some people think all bacteria are bad for you, this is nonsense. Most bacteria don't have anything to do with us, some are good for you and it would make you sick if they left you. But for some bacteria it would be better if you kept your distance. Having said so, our body encounters bacteria that can make us ill all the time, and yet we do not suffer bacterial infections for most of our time. That is because not every encounter results in disease, something to remember next time you read scary stories about Salmonella and the like being detected on door handles or shopping carts. Whether an encounter results in disease depends on a number of factors, such as how many bacteria enter your body, in what health state your body is, how well your immune system is working and whether you have already built up immunity against that kind of disease or not.
In case you are interested in disease-causing bacteria, this cateogory gives a good introduction. It only contains three exibits:
The result of a spreading disease can be an epidemic, as is explained in our display on epidemiology.
Once you have read these exhibits, you will realize how important it is to stay clear of certain pathogenic bacteria. In our category Food and water safety it is explained what you can do to decrease your risk of a bacterial infection. Don't forget to also read about the good bacteria in food.
But you are not helpless against pathogenic bacteria. Your body is well equipped to fight back, and that is explained in the category How we fight bacteria.