How infections spread

The chain of infection

An infection needs six things to happen in order: an infectious agent (such as a bacterium or virus), a reservoir where it lives, a way out of that reservoir, a way of travelling, a way into a new person, and a person who is susceptible. Infection control works by breaking at least one of those links.

Reservoirs are often people — including people with no symptoms — but they can also be food, water, equipment, surfaces, linen or waste. That is why you treat every person and every used item as potentially infectious, not just people who look unwell.

How germs travel

Contact is the most common route in everyday work. Direct contact is skin-to-skin; indirect contact is when germs move from a hand, glove or cloth to a surface and then to someone else. Hands are the single biggest vehicle for indirect spread.

Droplets from coughing, sneezing or talking travel a short distance and land on people or surfaces nearby. Some germs can also travel on much smaller airborne particles that hang in the air for longer and spread further, especially in poorly ventilated rooms.

Who is most at risk

Older people, young children, people with chronic illness, wounds, catheters or weakened immune systems are more likely to become seriously ill. The same germ that gives you a mild cold can put a frail resident in hospital.