GDA Nursing Class Notes 35


Infection is a medical term that refers to the invasion and multiplication of harmful microorganisms, such as bacteria, viruses, fungi, or parasites, within a host organism’s body. These microorganisms, often referred to as pathogens, can cause various types of illnesses or diseases as they reproduce and disrupt the normal functioning of the host’s tissues and organs. Infections can range from mild and localized, such as a common cold, to severe and systemic, such as sepsis. Proper hygiene, vaccination, and the use of antimicrobial agents are among the strategies employed to prevent and treat infections.


•Infections can be transmitted from one individual to another through various modes.

•Understanding the modes of transmission is crucial for preventing the spread of infections.

Some common modes of transmission

Direct Contact: Infections can spread through direct physical contact between an infected person and a healthy person. This includes activities like shaking hands, hugging, kissing, and sexual contact.

Fecal-Oral Transmission: Infections can spread when pathogens from feces are ingested. This can happen when contaminated food, water, or surfaces are touched and then the mouth is touched without proper hand hygiene.

Respiratory Droplets: Many infections are spread through respiratory droplets produced when an infected person coughs, sneezes, talks, or breathes.


•The chain of transmission refers to the sequence of events that must occur for an infection to spread from one person to another.

The chain of transmission typically involves several interconnected links

Infectious Agent: This is the microorganism that causes the infection, such as a bacterium, virus, fungus, or parasite. Different pathogens have varying modes of transmission and characteristics that affect how they spread.

Reservoir: The reservoir is the source of the infectious agent. It can be a human, animal, or environment (like contaminated water or soil) where the pathogen thrives and multiplies.

Portal of Exit: This is the way through which the infectious agent leaves the reservoir. Common portals of exit include respiratory secretions (coughs, sneezes), bodily fluids (blood, saliva), and open wounds.

Mode of Transmission: This refers to how the infectious agent is transmitted from the reservoir to a susceptible host. Different modes of transmission include direct contact, indirect contact, respiratory droplets, airborne transmission, vector-borne transmission, and more.

Portal of Entry: After transmission, the infectious agent must enter the body of a susceptible host. The portal of entry is the route through which this occurs, such as the mouth, nose, eyes, or broken skin.

Susceptible Host: A susceptible host is an individual who is vulnerable to the infection. Factors that affect susceptibility include a weakened immune system, lack of immunity to the pathogen, and overall health status.