Stage of infection

At this stage the infectious agent has entered the host's body and has begun multiplying. The entry and multiplication of an infectious agent inside the host is known as the stage of infection. For instance, a person who has eaten food contaminated with Salmonella typhii (the bacteria that cause typhoid fever) is said to be exposed; if the bacteria enter the cells lining the intestines and start multiplying, the person is said to be infected.

At this stage there are no clinical manifestations of the disease, a term referring to the typical symptoms and signs of that illness. Symptoms are the complaints the patient can tell you about (e.g. headache, vomiting, dizziness). Signs are the features that would only be detected by a trained health worker (e.g. high temperature, fast pulse rate, enlargement of organs in the abdomen).