An infective agent is an agent that if taken into the body can produce an infection

An infective agent is an agent that if taken into the body can produce an infection. This may be a bacterial, viral, fungal or parasitic infection.
There are four main routes through which infective agents may enter the body. Agents which enter through the nose can travel through the respiratory tract and into the lungs. This is the way that an upper respiratory tract infection, commonly known as a cold, coughs or influenza are caught.
Infective agents can enter the body through the mouth and travel down the digestive tract and into the stomach or intestines (known as the digestive system). This usually occurs when we ingest contaminated/out of date food or drink products in which bacteria have grown. Another way of pathogens entering the system this way is due to inadequate handwashing. When people do not wash their hands after going to the toilet and then put their hands in their mouth whilst eating there could be pathogens from faecal matter entering their mouth. These infective agents entering the digestive system tends to cause gastroenteritis (Verywellhealth 2018).
Infective agents can enter the body through break in a person’s skin. This is the main job of our skin – to protect us from infection. When someone has a cut, abrasion, bite, scratch or puncture to their skin this is a potential gateway for an infective agent to enter the body and get into a person’s bloodstream. This could also include cuts, scrapes, or sores in the mucous membrane that lines the mouth, nose or eye as this is another route for infection to enter the body. A common type of infection caught through skin breakages is Impetigo – which can be caused by staph or strep bacteria (Verywellhealth 2018).
Infective agents also enter the body through the urinary or reproductive systems. Urinary tract infections can be caused by pathogens from faeces being wiped into the urinary tract. Sexually transmitted diseases can enter the reproductive tract through sexual contact with another person and typically stay localised and effect the genitals, except for HIV, which can be carried in other bodily fluids, such as blood, saliva and semen, and enter the body into the bloodstream.