Infection Prevention and Control in the Healthcare Setting

Infection prevention and control (IPC) is the set of practices that stop pathogens moving between patients, healthcare workers and the environment of the facility. Its programme has two enduring pillars: surveillance, which measures how much infection is occurring, and isolation, which contains the patients who can transmit. Around these sit hand hygiene, outbreak management, staff health, environmental control and the safe supply of blood. Much of the evidence rests on understanding how organisms spread rather than on controlled trials, because healthcare-associated infections are individually uncommon and adequately powered isolation trials are rarely feasible.

The chain of infection

Every transmission event is a chain of linked steps, and IPC works by breaking whichever link it can reach. The chain runs from the infectious agent to its reservoir, which in a hospital is the infected or colonised patient, a healthcare worker, or a contaminated surface or device, then out through a portal of exit such as the respiratory or gastrointestinal tract, along a mode of transmission, into a portal of entry in the next person, and finally into a susceptible host whose risk depends on age, immune status and invasive devices.

Breaking any single link interrupts transmission. Reprocessing and environmental cleaning remove the reservoir, precautions and hand hygiene block the route, and vaccination reduces host susceptibility. The organising task of a facility programme is to identify which link is driving spread and to target it.

Standard precautions

Standard precautions apply to every patient, in every setting, at all times, because any patient may be colonised or infected without this being known. Their essential elements are hand hygiene, personal protective equipment (PPE), safe injection practice and respiratory hygiene.

Hand hygiene is the single most important measure, because most healthcare-associated infection is transmitted on the hands of staff. The target is the loosely attached transient flora picked up from patients and surfaces, not the resident skin flora. Alcohol-based hand rub is the routine agent, faster and more effective than soap and water and better tolerated by the skin. Soap and water is used when hands are visibly soiled, and is preferred after caring for a patient with Clostridioides difficile or norovirus, because alcohol is poorly active against spores and against non-enveloped viruses.

Hand hygiene is performed before touching a patient, before an aseptic task, after contact with body fluids, after touching the patient or their surroundings, and immediately after removing gloves.

Gloves are worn for anticipated contact with blood, body fluids, mucous membranes or non-intact skin, and are changed between a contaminated and a clean site on the same patient. Gloves do not replace hand hygiene, because hands are contaminated during removal and through unseen perforations.

Gowns, masks and eye protection are added when a procedure may splash or spray. Injection safety is a recurrent failure point: a needle and syringe are used for one patient only, single-dose vials are preferred and never shared, and blood-glucose meters and insulin pens are never shared between patients. Respiratory hygiene asks a coughing patient to cover the mouth, clean the hands and wear a surgical mask in shared areas.

Transmission-based precautions

When a patient has, or is suspected of having, an agent that standard precautions cannot fully contain, one of three transmission-based precautions is added to standard precautions according to how the agent spreads. Some agents need more than one category.

Precaution	Barrier	Room	Viral examples
Contact	Gloves and gown on entry	Single room or cohort	Respiratory syncytial virus, rotavirus, norovirus, hepatitis A virus, herpes simplex virus
Droplet	Surgical mask on entry	Single room, no special air handling	Influenza, mumps, rubella, parvovirus B19
Airborne	N95 respirator	Negative-pressure single room	Measles, varicella, disseminated zoster

Contact precautions address direct and indirect spread by touch, and are the commonest category, covering multidrug-resistant bacteria, C. difficile, and the enteric and skin viruses. Gloves and a gown are put on at the door and removed before leaving so that clothing is not contaminated, and non-critical equipment such as a stethoscope or blood pressure cuff is dedicated to the room.

Droplet precautions cover agents carried on large respiratory particles that fall to nearby surfaces rather than staying airborne, so a surgical mask on entry suffices and no special ventilation is needed.

Airborne precautions cover agents that remain suspended in tiny droplet nuclei and travel on air currents, requiring a negative-pressure room that exhausts to the outside, with at least six and preferably twelve air changes per hour, and a fit-tested N95 respirator. Classically the boundary between droplet and airborne spread is drawn at a particle size of about five micrometres, with droplet agents falling within roughly one to two metres. This division still structures the precaution categories, but it is a simplification: the exhaled plume is really a continuum of particle sizes rather than two clean classes.

Two escalations matter to virologists. Varicella and disseminated zoster require both airborne and contact precautions, and seasonal influenza, normally managed as a droplet infection, is handled with airborne precautions during aerosol-generating procedures such as bronchoscopy or intubation. A nonimmune worker should not enter the room of a patient with measles or varicella.

Respiratory transmission after SARS-CoV-2

The SARS-CoV-2 pandemic forced a reappraisal of how respiratory viruses spread. The weight of evidence now recognises that these viruses are shed predominantly in small particles that stay suspended and are inhaled, so a share of transmission once attributed to large droplets is in fact airborne. Influenza, respiratory syncytial virus and other respiratory viruses, long managed with droplet precautions, are increasingly understood to spread partly by this route, and national droplet-precaution guidance, though still in wide use, is now questioned.

Several practical lessons followed. SARS-CoV-2 is shed before symptoms begin, exposing contacts in the roughly two days before onset, which is why universal masking as source control was so effective at interrupting spread, and why admission testing and prompt isolation matter.

Confirmed cases are best placed in a negative-pressure airborne-infection isolation room where one is available, with staff in a particulate respirator, the N95 or a powered air-purifying respirator, plus eye protection, a gown and gloves. The pandemic also cast doubt on the long list of designated aerosol-generating procedures, since some may expose staff to no more infectious aerosol than the routine care of an infectious patient.

Healthcare-associated infection and surveillance

A healthcare-associated infection (HAI) is one that a patient acquires during care rather than bringing to it. The first purpose of surveillance is to establish the endemic rate, the background level of infection, because an outbreak is defined simply as a rate significantly above that baseline. Without a measured baseline, a cluster cannot be recognised as unusual.

Surveillance concentrates on the device-associated infections that carry the greatest preventable burden: central-line-associated bloodstream infection, ventilator-associated pneumonia and catheter-associated urinary tract infection, each expressed against the days a device was in place so that different units can be compared fairly. Standardised case definitions make those comparisons valid. The most productive modern approach is to monitor compliance with the steps of care, the insertion and maintenance bundles, and to feed that back to frontline staff, which drives improvement more reliably than reporting infection rates alone.

Outbreak investigation and response

An outbreak is suspected when the rate for a period rises above the range seen in previous years, or when a clinician or laboratory notices an unusual cluster.

Investigation confirms the outbreak against the endemic baseline, defines a case, and characterises the isolates. Molecular typing distinguishes a true point-source or transmission cluster, where the strains are identical, from a polyclonal rise that instead reflects a change in practice or an imported strain, and this shapes whether a case-control study is worthwhile. Whole-genome sequencing has become the front-line typing tool, rapid and detailed enough to be folded into routine surveillance and to supersede older fingerprinting methods.

Most healthcare outbreaks are contact-transmitted, so control rests on cohorting affected patients and the staff who care for them, intensified environmental cleaning, strict hand hygiene and contact precautions, and early warning to the laboratory to save isolates for typing.

Protecting the workforce

The IPC programme works closely with occupational health, which is the interface for staff immunity and exposure. Workers are screened at employment for immunity to measles, mumps, rubella, varicella and hepatitis B, tested for latent tuberculosis, and offered annual influenza and COVID-19 vaccination, since a susceptible or infectious worker is both a victim and a vector. After a percutaneous or mucosal exposure to blood, the worker is assessed for post-exposure prophylaxis against bloodborne viruses, and staff with transmissible infection are restricted from duty until no longer infectious.

Environmental controls, design and governance

The near-patient environment is a genuine reservoir, so routine cleaning and disinfection of surfaces, safe water and well-managed ventilation are part of IPC, not housekeeping apart from it. Hardy organisms such as Clostridioides difficile and the multidrug-resistant yeast Candida auris survive on surfaces for weeks, so the disinfectant must be matched to them.

Air handling matters most in the high-risk areas: negative pressure for airborne isolation, and protective positive-pressure environments for the profoundly immunocompromised. IPC input belongs early, when a facility is designed or renovated and when new equipment is procured, because a ward’s isolation capacity and a device’s reprocessing needs are cheaper to build in than to retrofit.

Surveillance data, audit of practice against policy, and investigation of any non-conformance close the loop, turning IPC from a set of rules into a monitored system.

Transfusion-transmissible viruses

Blood transfusion is a direct route into the bloodstream, so screening the blood supply is an IPC responsibility in its own right. Several viruses are transmissible by transfusion, chiefly human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV) and human T-lymphotropic virus (HTLV), with parvovirus B19 and, in immunocompromised recipients, cytomegalovirus also relevant. Donations are screened by serology together with nucleic acid amplification testing (NAT), which detects viral genome directly.

The residual risk is the window period: the interval after a donor is infected but before any test can detect the infection. NAT shortens this window by finding virus before antibody appears, but it cannot abolish it, so a small residual risk remains from donations given during that eclipse. When a donor is later found to be infected, a look-back traces the recipients of their earlier donations so that any infected recipient can be identified and managed. Donor selection that defers higher-risk donors complements testing by lowering the chance of a window-period donation entering the supply.

South African context

South African facilities apply the same two-tier precaution system within the framework of the National Institute for Communicable Diseases (NICD) and the National Department of Health (NDoH). Several viral infections relevant here are notifiable medical conditions, reported through the NICD system, and a suspected viral haemorrhagic fever triggers the country’s most stringent isolation, PPE and specimen-handling requirements, which are set out for South African facilities in the South African VHF Guidelines rather than repeated here.

The principles rehearsed during the COVID-19 response, tiered precautions, rational PPE use and cohorting of patients under investigation, remain sound even though the specific pandemic protocols have since been withdrawn and should not be treated as current policy.

The blood supply is managed by the South African National Blood Service (SANBS). Every donation is tested individually by both serology and individual-donation nucleic acid amplification testing (ID-NAT) for HIV, HBV and HCV, so the residual risk of transmitting these viruses is remote. It cannot reach zero, because a donation given in the window period may still test negative, so SANBS runs a look-back programme that traces the recipients of a donor’s earlier donations when a later donation tests positive for a transfusion-transmissible infection.

References and recommended reading

• Palmore TN. Infection Prevention and Control in the Health Care Setting. In: Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, 10th edition. Elsevier; 2025. The primary source for the surveillance, isolation and precaution framework, and the post-SARS-CoV-2 transmission reappraisal described here.
• Wang CC, Prather KA, Sznitman J, et al. Airborne transmission of respiratory viruses. Science 2021;373(6558):eabd9149. The review underpinning the shift toward recognising aerosol transmission of respiratory viruses.
• Richman DD, Whitley RJ, Hayden FG, editors. Clinical Virology, 4th edition. ASM Press; 2016. The source for the transfusion-transmissible viruses and window-period principles.
• South African National Blood Service and Western Cape Blood Service. Clinical Guidelines for the Use of Blood and Blood Products in South Africa, 6th edition. 2023. The source for South African donor testing, the residual risk of transfusion transmission, and the look-back programme.