Major infection routes and common infections that are spread through each route include

Contact infection

A transmission route with high frequency of transmission. Mostly through fingers, food and apparatus.

Examples: Norovirus, Methicillin-resistant Staphylococcus aureus (MSRA), Pseudomonas aeruginosa

Droplet infection

Through inhalation of droplets of a cough or sneeze. Happens within 1 minute of droplet expulsion as the droplets fall on the floor after that.

Examples: Influenza, epidemic parotitis, rubella, Legionella bacteria

Airborne infection

Developed through inhalation of a pathogen while it’s suspended in the air for a long time.

Examples: Tuberculosis, measles, chickenpox

Percutaneous infection

When a pathogen enters the body through a wound, bite or sting by a mosquito or any other insect or animal.

Examples: Malaria, dengue, Japanese encephalitis

Blood-mediated infection

When blood, blood fluid or other secretions are contaminated with a pathogen that enters through a needle prick or similar.

Examples: Hepatitis B, Hepatitis C, HIV

The chain of infection (also known as chain of transmission) of an infectious disease

1. Infectious Agent
   This is the pathogen that causes infection.
   Examples: Bacteria, Fungi, Viruses, Parasites
   
2. Reservoirs
   These are the places where the pathogen is stored.
   Examples: People, Water, Food
   
3. Portals of Exit
   These are the ways through which the pathogen can escape from its reservoir.
   Examples: Blood, Secretions, Excretions, Skin
   
4. Modes of Transmission
   These are the ways in which the pathogen can be transmitted.
   Examples: Contact, Droplet, Airborne
   
5. Portals of Entry
   These are the ways through which the pathogen can enter a host.
   Examples: Respiratory, Gastrointestinal, Broken Skin
   
6. Susceptible Host
   A care receiver who’s particularly vulnerable to getting infected with a pathogen.
   Examples: People with diabetes, burns, surgery, advanced age or any other factor that can weaken immune system.

Infection prevention measures broadly fall into 3 categories:

1. Removing the infection source
2. Breaking the chain of infection
3. Enhancing the host’s resistance

Removing the infection source

Remove all possible sources of infection such as

• Vomit
• Excreta (urine, stool)
• Blood and any other body fluid (e.g. sputum, pus)
• Used appliances (e.g. injection needle, gauze)
• Food handled by fingers contacting the above

Wear gloves when handling the above. After removing gloves, remember to wash hands and disinfect fingers.

Breaking the chain of infection

Sometimes it’s not feasible to remove the source of infection. If so, there are ways to break the chain of infection such as

• Enforcing regular handwashing with warm water and soap
• Cleaning the environment as frequently as possible
• Wearing appropriate gloves
• Wearing masks, aprons or gowns to further reduce chances of spread
• Observe cough and respiratory etiquette, e.g. don’t cough, sneeze or blow near another person

Enhancing the care receiver’s resistance

The care receiver’s ability to withstand infection can be strengthened by

• Getting flu shots and other recommended vaccines regularly
• Maintaining a healthy diet
• Exercising regularly
• Staying hydrated with 7 to 8 glasses of water a day
• Sleeping 7 to 8 hours a day
• Reducing stress

Article reviewed by David Tay, Senior Principal Educator (Nursing and Prehospital Care), HMI Institute.