Infection Control and Prevention

Infection control and prevention encompasses the practices used to stop pathogens from spreading, both in healthcare settings and in the community. It works by breaking links in the chain of infection — removing or isolating sources, interrupting transmission routes, and protecting susceptible hosts — through measures ranging from hand hygiene and precautions to vaccination and environmental controls.

Definition

Infection control and prevention is the set of evidence-based principles and practices aimed at preventing the transmission of infectious agents to and among patients, healthcare workers, and the wider population by interrupting the chain of infection.

Scope

This entry covers the principles behind infection prevention: standard and transmission-based precautions, hand hygiene, isolation, environmental and sterilisation measures, and population-level protection through immunisation and herd immunity. It is a conceptual reference and does not prescribe specific control protocols for any institution or patient.

Core questions

• At which point in the chain of infection does a given measure act?
• What distinguishes standard precautions from transmission-based precautions?
• Why is hand hygiene considered a cornerstone of healthcare-associated infection prevention?
• How do vaccination and herd immunity protect populations beyond the individual?

Key concepts

• Chain of infection
• Standard precautions
• Transmission-based precautions (contact, droplet, airborne)
• Hand hygiene
• Isolation and cohorting
• Sterilisation and disinfection
• Vaccination and herd immunity

Key theories

Breaking the chain of infection

Prevention is framed as interrupting one or more links in the chain — agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host — so that measures are chosen according to which link they break.

Herd immunity

When a sufficient proportion of a population is immune, susceptible individuals gain indirect protection because the agent can no longer sustain transmission, lowering the effective reproduction number below the threshold for spread.

Mechanisms

Control measures map onto the chain of infection. Source-directed measures isolate or treat infectious individuals; route-directed measures interrupt transmission through hand hygiene, personal protective equipment, ventilation, disinfection, and safe handling of food, water, and sharps; and host-directed measures protect the susceptible through vaccination and, at population scale, herd immunity. Hand hygiene is emphasised because the hands of healthcare workers are a well-documented vehicle for transferring pathogens between patients, and improving hand-hygiene practice interrupts this route (Pittet, 2006). At the population level, raising the immune fraction reduces the effective reproduction number, and during epidemics non-pharmaceutical control measures can be assessed by their effect on transmission (Lipsitch, 2003; Fine, 1993).

Clinical relevance

Infection prevention underpins safe patient care and explains why measures such as hand hygiene, isolation precautions, sterile technique, and immunisation programmes exist. This entry presents the principles in general, reference terms and is not a directive on which precautions to apply to a specific patient or facility.

Epidemiology

Healthcare-associated infections are a substantial, partly preventable burden, and hand-transmission of pathogens during patient care is a major contributor that improved hand-hygiene practice can reduce (Pittet, 2006). During community epidemics such as SARS, layered non-pharmaceutical measures were shown to lower transmission, illustrating prevention at the population scale (Lipsitch, 2003).

History

Modern infection control descends from nineteenth-century advances in antisepsis and asepsis and from early recognition that clean hands reduce transmission in care settings. Through the twentieth century these insights were systematised into precautions, sterilisation standards, and immunisation programmes, and quantitative epidemiology supplied the herd-immunity and reproduction-number framework that links individual measures to population protection.

Debates

How are precaution categories matched to uncertain transmission routes?

Because the relative contribution of droplet and airborne spread is contested for some respiratory pathogens, the choice between droplet and airborne precautions can be uncertain, affecting which protective measures are recommended.

Key figures

• Didier Pittet
• Paul Fine
• Marc Lipsitch
• Roy Anderson

Seminal works

• pittet-2006
• fine-1993
• anderson-may-1991

Frequently asked questions

Why is hand hygiene considered so important in healthcare?

The hands of healthcare workers can carry pathogens from one patient or surface to another, so cleaning hands at the right moments interrupts a major route of healthcare-associated transmission.

What is herd immunity?

It is the indirect protection that susceptible people gain when enough of the surrounding population is immune that the pathogen can no longer spread efficiently, reducing transmission below the level needed to sustain an outbreak.