Mapping out the causes of infectious diseases: A case study on the multiple factors involved in salmonella enteritidis infections

Infectious diseases can be transmitted by various transmission routes, including via food, water or air, through zoonotic contact, by direct contact with other infected people via skin, direct mucosal contact, respiratory secretions or sexual contact, from the environment within buildings including hospitals, as well as from the natural environment. Direct injection of pathogens into the body can occur from trauma, injection by syringe, biting insects or body piercing. Providing epidemiological evidence that a particular pathogen can infect people through a particular transmission route is obtained through case evidence, outbreaks and analytical studies (see Chapter 2) or through using animal models of transmission. This section examines the multiple factors that can contribute to an outbreak, using a Salmonella infection as an example.