The chain of infection
An infection happens when germs (bacteria, viruses, fungi or parasites) get into the body and multiply. For this to happen, six links must join up:
- Germ (infectious agent)
- Reservoir: where it lives and grows, such as a sick person, dirty water or a surface
- Way out (portal of exit): coughs, blood, stool, wounds
- Way of spread (mode of transmission): touch, droplets, air, food, needles, insects
- Way in (portal of entry): mouth, nose, cuts, catheters
- Weak host (susceptible host): babies, old people, people after surgery
Infections caught inside a hospital are called hospital-acquired (healthcare-associated) infections. Infection control is everything we do to stop them.
Breaking the chain: standard precautions
Standard precautions are used with every patient, because you cannot see who carries germs.
- Hand hygiene: soap and water for 40โ60 s, or alcohol hand rub for 20โ30 s.
- PPE: gloves, gown or apron, mask, goggles or face shield.
- Respiratory hygiene: cover coughs and sneezes, give masks to coughing patients.
- Cleaning: clean (remove dirt) โ disinfect (kill most germs) โ sterilise (kill all germs, e.g. autoclave at about 121 ยฐC).
- Safe sharps: never recap a used needle; drop it into a puncture-proof sharps box.
- Isolation for some infections, such as tuberculosis.
The 5 moments for hand hygiene
- Before touching a patient
- Before a clean or aseptic task
- After a risk of body-fluid exposure
- After touching a patient
- After touching the patient's surroundings
PPE order
On (donning): gown โ mask โ goggles/face shield โ gloves. Off (doffing): gloves โ goggles โ gown โ mask, and clean hands at the end and whenever hands get dirty.
Biomedical waste
Waste touched by blood or body fluids can spread infection, so it is sorted at the point where it is made. Colours differ a little between countries; a common scheme (used in India) is:
- Yellow: body parts, soiled dressings and cotton, some medicines
- Red: contaminated plastics such as tubes, bottles, gloves
- White (translucent, puncture-proof): needles, blades and other sharps
- Blue: broken or used glass such as vials
Ordinary kitchen and paper waste goes in the general bin. Bags are filled only three-quarters and labelled.
Safety at the workplace
A hospital can hurt its own workers. Common hazards and safe actions:
- Slips and falls: wipe spills at once, use a wet-floor sign, keep corridors clear.
- Needle-stick injury: no recapping; if pricked, wash with soap and water, let it bleed a little, report at once for follow-up.
- Fire: remember RACE (Rescue, Alarm, Contain, Extinguish) and PASS for an extinguisher (Pull, Aim, Squeeze, Sweep).
- Back injury: bend the knees, keep the back straight, hold loads close, use slide sheets and ask for help.
- Chemicals and electricity: read labels, never use wet hands on switches.
- Violence and stress: stay calm, keep an exit, report incidents.
Health workers are also protected by vaccines (such as hepatitis B) and by reporting every accident.
Key formulas and definitions
- Chain: germ โ reservoir โ way out โ spread โ way in โ weak host
- Break ANY one link โ infection stops
- Hand wash 40โ60 s; alcohol rub 20โ30 s
- 5 moments: 2 befores (patient, clean task) + 3 afters (fluids, patient, surroundings)
- PPE on: gown โ mask โ goggles โ gloves; off: gloves first
- Clean < disinfect < sterilise (kills all germs)
- Fire: RACE; extinguisher: PASS
Worked examples
1. A nurse takes a patient's pulse, then goes straight to the next patient. Which link is not broken, and how should it be?
The way of spread (hands carry germs). She should clean her hands after touching the patient (moment 4) and before touching the next patient (moment 1).
2. Into which bin do these go: a used syringe needle, a blood-soaked cotton swab, a used IV tube?
Needle โ white puncture-proof sharps container; cotton swab โ yellow; IV tube โ red (in the colour scheme shown).
3. A worker is pricked by a used needle. List the right steps.
Do not suck or squeeze hard. Wash the area with soap and running water, let it bleed a little, report to the in-charge at once, and go for testing and preventive treatment as advised.
Common mistakes
- Thinking gloves replace hand hygiene: clean hands before putting gloves on and after taking them off.
- Recapping a used needle with two hands: this causes most needle-stick injuries.
- Taking off the mask first: gloves are the dirtiest item and come off first.
- Putting sharps in a plastic bag: needles go only into a puncture-proof container.