Infection Prevention & Control: Questions

a. Wash the wound and encourage bleeding, then report and document the exposure to occupational health.

b. The source is HIV and HBsAg negative, so no HIV or HBV prophylaxis is indicated. The HCV antibody shows exposure but not necessarily active infection, so send source HCV RNA to confirm current infectivity.

c. There is no effective post-exposure prophylaxis or vaccine for HCV. Take a baseline HCV serology from the worker, then follow up with HCV RNA at about six weeks and antibody at three to six months, and treat early with direct-acting antivirals if seroconversion occurs.

Spaulding sorts items by what they touch, and each category maps to a level of pathogen elimination with a characteristic procedure or agent.

• Sterilisation (critical items entering sterile tissue): steam autoclaving is the standard, with ethylene oxide or hydrogen peroxide gas plasma for heat-sensitive items.
• High-level disinfection (semi-critical items touching mucous membranes): a chemical high-level disinfectant such as glutaraldehyde, ortho-phthalaldehyde (OPA) or peracetic acid.
• Low-level disinfection (non-critical items touching intact skin): an environmental disinfectant such as a quaternary ammonium compound or 60 to 90% alcohol.

RSV spreads by contact with respiratory secretions and contaminated surfaces, so contact precautions anchor the answer.

• Contact precautions with gloves and gown on entry, and hand hygiene on leaving.
• Single room or cohorting of RSV cases, with dedicated equipment and minimal transport.
• Exclude symptomatic staff, restrict visitors, and clean the near-patient environment.
• Add droplet precautions for procedures that generate respiratory secretions.

A complete answer names the important nosocomial viruses and their burden, then the layered measures that prevent spread.

• Respiratory viruses, respiratory syncytial virus (RSV) and influenza, spread readily on paediatric and elderly wards.
• Enteric viruses, norovirus and rotavirus, cause explosive ward outbreaks.
• Bloodborne viruses, hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV), follow sharps injuries and unsafe injection.
• Varicella-zoster virus (VZV) and measles threaten nonimmune patients and staff.

Prevention is layered: hand hygiene above all, standard precautions for every patient, transmission-based precautions matched to route, healthcare worker vaccination, exclusion of symptomatic staff, environmental cleaning, and surveillance with prompt outbreak response.

Varicella is airborne, so it needs more than the skin precautions HSV requires.

• Varicella requires both airborne and contact precautions: a negative-pressure isolation room, only immune staff entering, and prophylaxis or vaccination for exposed nonimmune contacts, on a base of hand hygiene and standard precautions.
• HSV is not airborne, so standard precautions suffice, with contact precautions added for neonatal, disseminated or severe mucocutaneous lesions.

Varicella requires both airborne and contact precautions, because the virus spreads in droplet nuclei and by contact with vesicle fluid. Disseminated zoster is handled the same way.

Any single category, or standard precautions alone, leaves one route uncovered.

An item that touches mucous membranes but not sterile tissue is semi-critical and needs at least high-level disinfection. After disinfection it is rinsed, ideally with sterile water, to avoid recontamination.

It is neither critical (no entry into sterile tissue) nor non-critical (it exceeds intact-skin contact).

Norovirus spreads by the faecal-oral route and contaminated surfaces, so contact precautions with gloves and gown are required, alongside soap-and-water hand hygiene. It has a strong propensity for ward outbreaks.

It is not airborne or droplet-spread, and standard precautions alone are insufficient during an outbreak.

Glutaraldehyde coagulates blood and fixes tissue to surfaces, so instruments must be thoroughly cleaned first. It also irritates the airway and can cause colitis if inadequately rinsed.

It is kind to materials rather than corrosive, is broadly virucidal, and does not bleach fabric.

Candida auris persists on surfaces and resists some routine disinfectants, so a hospital disinfectant effective against Clostridioides difficile spores is recommended for its rooms. Chlorine, accelerated hydrogen peroxide and quaternary-alcohol products inactivate it rapidly.

Agents chosen only for enveloped viruses or ordinary vegetative bacteria may not clear this hardy yeast.

Quaternary ammonium compounds inactivate enveloped viruses but not the small non-enveloped viruses, so norovirus can survive a routine surface wipe. This is why agent choice matters for enteric-virus outbreaks.

Influenza, human immunodeficiency virus, herpes simplex virus and the coronavirus are all enveloped and readily inactivated.

Varicella-zoster immunoglobulin, given as soon as possible and ideally within 96 hours of exposure, is the mainstay for high-risk susceptible contacts: susceptible pregnant women, the immunocompromised, and neonates whose mothers develop varicella around delivery.

The live vaccine is contraindicated in pregnancy, and immunoglobulin attenuates rather than always prevents disease.

Soap and water is preferred after caring for a patient with Clostridioides difficile, because alcohol is poorly active against spores and the mechanical washing helps remove them. The same applies after norovirus, a non-enveloped virus.

Alcohol rub is the routine agent otherwise, but it and the other waterless options do not remove spores.

Contaminated endoscopes have caused more healthcare-associated outbreaks than any other medical device, because their long narrow channels trap soil and resist inspection. Meticulous cleaning, disinfection, rinsing, drying and vertical storage are all required.

They are reusable semi-critical items needing high-level disinfection, not gas sterilisation, and can transmit bacteria, viruses and fungi.

Ethylene oxide is flammable and a known human carcinogen, so residual gas must be driven off by aeration before an item is safe to use. This makes each cycle slow.

It is in fact highly penetrating and sporicidal, and it is not corrosive to steel in the way described.

High-level disinfection kills all microorganisms except large numbers of bacterial spores. That single exception is what separates it from sterilisation.

Viruses, vegetative bacteria, mycobacteria and fungi are all within its range.

Brain, spinal cord and eye are the high-risk tissues that, from a patient with known or suspected prion disease, trigger special reprocessing of critical or semi-critical instruments. The instrument is kept moist, then decontaminated by sodium hydroxide with autoclaving or extended steam at up to 134 °C.

Liver, kidney, lung and bone marrow are not designated high-risk tissues for prion transmission.

Nucleic acid amplification testing detects viral genome directly, appearing before antibody, so it shortens the infectious window. It complements, rather than replaces, serology and donor selection.

It neither abolishes all risk nor is limited to one virus, and it can be run on individual donations, not only pools.

An outbreak is a rate of infection significantly above the endemic baseline, which is why surveillance first establishes that baseline rate. Without it, a cluster cannot be judged unusual.

A single case, a fixed time window, an intensive-care location or a shared organism does not by itself define an outbreak.

The reservoir is where the agent persists, which in a hospital is an infected or colonised patient, a healthcare worker, or a contaminated surface or device. Removing or isolating the reservoir is one way to break the chain.

The portals, the transmission route and the susceptible host are the other, separate links in the chain.

Spaulding graded reprocessing by the infection risk of what an item touches, not by what the item is made of. Contact with sterile tissue, mucous membranes or intact skin sets the required level.

Material, cost, ward and warranty are irrelevant to the classification.

Ortho-phthalaldehyde is contraindicated for cystoscopes, following anaphylactic reactions in bladder-cancer patients undergoing repeated cystoscopy. It otherwise acts fast and needs no activation, but it stains proteins and skin grey.

The other endoscopes listed are not subject to this specific contraindication.

A person with chickenpox is infectious from about two days before the rash appears until the last lesion has crusted over. Transmissibility before the rash is what makes the disease so difficult to contain, and a patient is no longer infectious once every lesion has dried.

Surveillance focuses on device-associated infections, chiefly central-line bloodstream, ventilator-associated and catheter-associated urinary infection, because they carry the greatest preventable burden. Rates are expressed per device-day for fair comparison.

The other options are not the priority targets of healthcare-associated infection surveillance.

The residual risk is the window period: a donation given after infection but before any test can detect it. Nucleic acid testing shortens this window but cannot close it entirely.

Labelling errors, bacterial contamination, plasma reactions and storage lesions are separate transfusion issues, not the viral residual risk.

The weight of evidence now holds that respiratory 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. Droplet-precaution guidance for these viruses is now questioned.

Blood, faeces and skin scales are not the main vehicles for respiratory-virus spread.

Standard precautions apply to every patient, in every setting, at all times, because any patient may be colonised or infected without this being known. They are the baseline on which transmission-based precautions are added.

Restricting them to known-infected, immunocompromised, intensive-care or isolated patients would miss the undiagnosed carrier.

Seasonal influenza is a droplet infection, needing a surgical mask on entry and no special ventilation. It escalates to airborne precautions only during aerosol-generating procedures such as bronchoscopy or intubation.

Newer evidence suggests a real airborne contribution, and this guidance is under review, but droplet precautions remain the standing recommendation outside aerosol-generating procedures.

A duodenoscope reaches the biliary tree through the duodenum, so it effectively enters sterile tissue and meets the definition of a critical item that should be sterilised. More than twenty-five outbreaks of multidrug-resistant organisms, several despite correct high-level disinfection, drove this shift.

Treating it as semi-critical, non-critical or non-invasive underestimates the risk, and intermediate is not a Spaulding category.

SARS-CoV-2 is shed before symptoms begin, exposing contacts in the roughly two days before onset, so universal masking as source control interrupted spread that testing of symptomatic patients would miss.

Already-isolated, recovered and vaccinated people are not the reason masking worked, and the virus is not a bloodborne carrier state.

Sterilisation destroys all microbial life, including bacterial spores, whereas high-level disinfection kills everything except large numbers of spores. Sporicidal activity is the dividing line between the two.

Heat stability, the site contacted, the item type and the need for cleaning do not define the distinction.

The hospital environment often carries SARS-CoV-2 genetic material but rarely viable virus, and the fomite route plays only a limited part, so an ordinary hospital disinfectant from the regulator’s emerging-viral-pathogen list, applied to high-touch surfaces, is sufficient.

Sterilising all surfaces is unnecessary, bleach is not uniquely required, fomites are not the main route, and surfaces still need routine disinfection.

No-touch technologies supplement, but do not replace, manual cleaning, and are reserved for terminal decontamination of rooms that housed patients with persistent pathogens. They act only on surfaces a device can reach.

They neither sterilise a whole room nor are used on skin, and they do more than remove dust.

Breastfeeding is the principal route of vertical transmission, with a risk of around 20 to 30% that rises with prolonged feeding and a high maternal proviral load; avoiding breastfeeding is a key preventive measure.

A large blood spill is decontaminated with a 1:10 dilution of household bleach, and a small spill with 1:100. Hypochlorite is fast, cheap and broadly virucidal, including against non-enveloped viruses.

More dilute solutions are too weak for a large spill, and undiluted bleach is unnecessary and more corrosive.

A surgical implant enters sterile tissue, making it a critical item that must be sterile. Critical items are bought sterile or steam-sterilised where the materials allow.

A laryngoscope blade is semi-critical, while a cuff, stethoscope and bedpan are non-critical.

Hydrogen peroxide gas plasma cannot process cellulose materials such as paper and linen, and it has lumen-length limits. It works below 50 °C with no toxic residue and no aeration.

Metal and synthetic-polymer items are compatible with the process.

Whole-genome sequencing is now the front-line typing tool, rapid and detailed enough to be folded into routine surveillance and to supersede older fingerprinting methods. It resolves whether isolates share a single source.

Gel electrophoresis, phage typing, serotyping and antibiogram comparison are older, lower-resolution approaches.

A single-dose vial is used once, for one patient, and a needle and syringe serve only one patient, because reuse transmits bloodborne viruses. Blood-glucose meters and insulin pens are likewise never shared.

Reusing syringes, sharing vials or meters, and hand-recapping needles are all unsafe.

The lipid envelope is the vulnerability: enveloped viruses are the least resistant, as alcohols, hypochlorite and even quaternary ammonium compounds disrupt the envelope. Human immunodeficiency virus, hepatitis B virus and influenza are all easy targets.

Non-enveloped viruses are harder, not easier, to inactivate, and genome type and mutation rate are irrelevant to chemical susceptibility.

Airborne precautions require a fit-tested N95 respirator, which filters fine particles and seals to the face. A surgical mask does not protect against droplet nuclei.

Cloth coverings, surgical masks and face shields alone are inadequate for an airborne agent.

Steam under pressure is the most widely used and dependable method: non-toxic, inexpensive, rapidly sporicidal and well penetrating. It runs at 121 °C or 132 °C and is least affected by organic soil.

The low-temperature and chemical methods exist mainly for heat-sensitive items, and ultraviolet does not sterilise instruments.

Measles spreads in droplet nuclei that stay suspended, so it needs airborne precautions with a negative-pressure room and an N95 respirator. Nonimmune staff should not enter.

Droplet, contact or standard precautions alone would not contain an airborne agent.

Healthcare workers are screened for immunity to measles, mumps, rubella, varicella and hepatitis B at employment, with hepatitis B vaccination given to the non-immune, plus annual influenza vaccination. A susceptible worker is both at risk and a potential vector.

Yellow fever, rabies, typhoid and cholera vaccines are travel or exposure specific, not routine occupational requirements.

Alcohol at 60 to 90% is rapidly bactericidal, tuberculocidal and virucidal but is not sporicidal, so it cannot sterilise. It also evaporates quickly, making a long wet contact time hard to maintain.

Staining, tissue fixation and light inactivation are properties of other agents, not alcohol.

Residual organic soil both physically shields microorganisms and chemically inactivates many germicides, so cleaning is the indispensable first step. Soil left to dry becomes far harder to remove, so instruments are kept moist until cleaned.

Cleaning neither sterilises on its own nor replaces disinfection, and dried blood impairs rather than aids the process.

Gloves do not replace hand hygiene: hands are contaminated during glove removal and through unseen perforations. Hand hygiene therefore follows every glove use.

Gloves are single-use, are required for body-fluid contact, and do not themselves increase skin flora.

A complete answer pairs each route with its preventive measure.

• Breastfeeding, the main route of mother-to-child transmission: prevented by antenatal screening and by avoiding, or shortening, breastfeeding by infected mothers.
• Sexual contact, transmitted more efficiently from male to female: reduced by condom use.
• Cellular blood products, organ transplantation and shared needles: near-eliminated by screening blood and organ donors, and by safe-injection or needle-exchange programmes. Cell-free plasma carries little risk.

There is no licensed vaccine, though one is considered feasible.