A pathogen is any organism that causes disease. Fungi, viruses and bacteria are some of the most common examples of pathogens.
Pathogens spread in several different ways. Forms of person-to-person transmission include air, saliva, touch and the exchange of contaminated body fluids. An example of person-to-person transmission is someone with the cold virus coughing or sneezing on someone, allowing the germ to infect another person.
Some pathogens are found in contaminated food and water. Tainted beef, for example, may contain salmonella, E. coli or other types of harmful bacteria. Insects are also able to transmit infection. People are infected with malaria when they are bitten by infected mosquitoes.
Although many pathogens are carried by living organisms, others are transmitted by fomites. A fomite is any object that carries pathogens. Stuffed animals, towels and sheets are examples of fomites. Athlete's foot, which is caused by a fungus, can be spread by sharing towels.