Human Pathogenic Bacteria Human Pathogenic Bacteria - Index Page Human pathogens are those organisms which cause disease in humans. Certain viruses, bacteria, protozoa, round worms, flatworms, and insects can live inside humans. Most bacteria that live on the skin or in the gut of humans are harmless or beneficial. Some are usually harmless, but can cause disease under certain conditions. Some species of bacteria are known as pathogens but affect small numbers of humans.
Some species are highly pathogenic and are lethal for a high percentage of the humans they infect.
Some are highly contagious, but rarely cause death. Some bacteria that caused terrible epidemics in the past are today much less dangerous. Some that cause problems today were relatively harmless in the past. If childern want to study pathogens, for example to study Kochs Postulates, then work with plant pathogens as they seldom cause any problem in humans. For example you might start with a rotten apple or other fruit, but avoid dusky molds and dry moldy piles of leaves and grass.