Human immunodeficiency virus

Associated infections

• Acute HIV (seroconversion) illness
• Chronic HIV infection
• Acquired immunodeficiency syndrome (AIDS)
• Opportunistic infections secondary to immunosuppression
• HIV-associated malignancies

Transmission route

HIV is transmitted through the exchange of infected body fluids, principally blood, semen, vaginal secretions and breast milk. Recognised routes are unprotected sexual contact, mother-to-child transmission during pregnancy, delivery or breastfeeding, sharing of contaminated injecting equipment, transfusion of unscreened blood, and unsafe medical, dental or injection procedures. Transmission efficiency varies substantially by route and is strongly influenced by the source viral load, being highest during primary infection and advanced disease when viraemia peaks, and effectively absent where treatment has produced sustained viral suppression. Concurrent sexually transmitted infections, mucosal inflammation and mucosal trauma increase the risk of sexual acquisition.

HIV is not transmitted by casual contact such as hugging, handshakes or sharing food and utensils, nor by coughing, sneezing, insect bites, shared toilets or contact with intact skin. Saliva, tears, sweat and urine are not implicated in the absence of visible blood. These facts are worth stating plainly in a clinical setting because misconceptions about environmental and casual transmission persist and continue to generate unnecessary and stigmatising variations in practice, such as scheduling patients last on a list or applying additional cleaning regimens that have no evidential basis.

In occupational settings the average risk of transmission after percutaneous exposure to HIV-infected blood is approximately 0.3%, substantially lower than for hepatitis B, and lower still for mucous membrane exposure. Risk within that average is modified by the depth of the injury, whether the device was hollow-bore and visibly bloodstained, whether it had been in a source vessel, and the source viral load. Prompt post-exposure prophylaxis further reduces risk substantially and should be commenced as soon as possible after a significant exposure rather than deferred pending source testing. Documented occupational seroconversions in healthcare workers are rare and have overwhelmingly followed hollow-bore needlestick injury rather than contact with contaminated instruments or surfaces. Patient-to-patient transmission in procedural settings is correspondingly rare, and where it has been alleged the mechanisms implicated are the same unsafe injection and instrument reprocessing practices that transmit hepatitis B and C.

Relevance in endoscopy and reprocessing

The measures that control HIV in endoscopy, CSD and dental settings are the same measures that control hepatitis B and C, and no additional or separate precaution is required for a patient known to be HIV positive. Standard precautions applied to every patient, on the basis that infection status is frequently unknown, are the operative control: appropriate personal protective equipment, safe sharps handling with point-of-use disposal, avoidance of needle recapping, prompt containment and decontamination of blood spills, and single-use injectable preparations wherever possible. Because HIV is fragile and readily inactivated, a correctly executed cleaning and disinfection sequence carries a very wide margin of safety against it; a process validated to control hepatitis B virus, which is far more environmentally robust and infectious at lower inoculum, will control HIV comfortably.

The practice failures relevant to HIV are consequently identical to those identified in bloodborne virus incidents generally: omission or abbreviation of manual cleaning of the endoscope working channel before disinfection, use of reusable biopsy forceps or other tissue-penetrating accessories without an intervening sterilisation cycle, reprocessing without leak testing so that channel damage goes undetected, inadequate drying and storage, and unsafe injection practice during sedation, particularly the re-entry of a used syringe into a multi-dose vial subsequently accessed for another patient. Reuse of single-patient devices such as lancing devices and insulin pens is a further recognised failure in shared-care settings. Notably, scheduling a known HIV-positive patient at the end of a list, applying an extended disinfection cycle or using additional chemical agents are not evidence-based measures, do not appear in AS 5369:2023, and should be discontinued where they persist, since they substitute ritual for the steps that actually matter.

The reprocessing-failure and exposure pathway governs the response to an incident. For a staff exposure, the sequence is immediate first aid, prompt risk assessment, urgent occupational health referral for consideration of post-exposure prophylaxis and baseline serology, source-patient assessment and testing where consent permits, and documented follow-up serology at the intervals specified by the jurisdictional protocol. For a suspected reprocessing breach, the implicated device and accessories should be quarantined, reprocessing and traceability records for the affected period retrieved, the exposed patient cohort defined by working back to the last compliant cycle, and the reprocessing record audited against AS 5369:2023 and the manufacturer's instructions for use. The state or territory public health unit should be engaged early. Where a breach is substantiated, a structured look-back and patient notification is undertaken, with affected patients offered baseline HIV, HBV and HCV testing, repeat testing after the relevant window periods, counselling and a defined referral route, and with any apparent transmission investigated by sequencing before an epidemiological link is accepted.

Interpreting a detection

HIV is not a rinse-water surveillance target and appears in no water quality parameter set applied under AS/NZS 5369. Rinse-water monitoring in endoscopy and CSD is designed to detect organisms that colonise water systems and can be deposited on a reprocessed device at the final wetted step, principally Pseudomonas aeruginosa and other Gram-negative water organisms, non-tuberculous mycobacteria and Legionella species, together with total viable count, conductivity and endotoxin as indicators of treatment performance and system condition. A retrovirus that replicates only within human lymphoid cells and is inactivated within a short time outside the host is not recoverable from that matrix and is never included in the test panel.

Where HIV nucleic acid is reported on a water or rinse-water sample, the finding is almost certainly a laboratory or sampling artefact rather than evidence of a contaminated system. HIV RNA and proviral DNA assays are highly sensitive and are performed in laboratories that simultaneously process large numbers of clinical plasma specimens, quantified control materials and, in some settings, synthetic template. Specimen carryover during extraction or pipetting and amplicon contamination of reagents, consumables and work surfaces are established failure modes in that environment and are far more plausible than genuine contamination of a treated water loop. Detection of nucleic acid does not indicate the presence of infectious virus in any case, and a fragile enveloped retrovirus would not remain viable in water even if it were somehow introduced.

Resolution belongs with the laboratory, not the water safety group. Confirm sample identity and matrix first: verify the chain of custody, sample point identifier, collection date and time, container type and labelling, and confirm that water rather than a misrouted clinical specimen was tested. Then determine whether the assay was validated for environmental matrices, since HIV assays are validated on plasma and their extraction efficiency, internal control behaviour and inhibition profile on a low-biomass water matrix are undefined; review the extraction blank and no-template control and check the sample's position in the run relative to any high-titre clinical specimen. Resample the same point using fresh, unopened consumables and an independent sampling kit, splitting the resample between two laboratories where practicable. Escalate the finding to laboratory quality management, which owns specimen segregation, workflow design and contamination control, and record it as a laboratory quality issue rather than a water quality exceedance. The water safety group should be informed for completeness but should not initiate flushing, disinfection, filter changes or system shutdown, and the result should not be trended against the facility's rinse-water data. Any genuine concern about HIV exposure or transmission at the facility is investigated separately and promptly through the occupational exposure and reprocessing-failure pathway, since that pathway carries time-critical clinical actions, particularly post-exposure prophylaxis, that a water investigation would only delay.

Antimicrobial resistance

Antiretroviral drug resistance is well characterised and clinically important. All antiretroviral classes, including nucleoside and non-nucleoside reverse transcriptase inhibitors, protease inhibitors and integrase strand transfer inhibitors, are susceptible to the emergence of resistant virus. The mechanism is straightforward: reverse transcriptase is error-prone and generates a large and diverse viral population, so that where drug pressure is present but viral replication is not fully suppressed, variants with reduced drug susceptibility are selected and come to dominate. Complete suppression of replication, by contrast, removes the substrate for selection, which is why sustained undetectable viral load is the principal means of preventing resistance emergence.

Resistance may be transmitted at the time of infection or acquired during treatment. Acquired resistance is driven by incomplete viral suppression arising from suboptimal adherence, drug interactions that lower antiretroviral concentrations, treatment interruption, drug supply interruption or inadequate regimen potency. Transmitted resistance, present in a person before any therapy, influences the choice of initial regimen and is one rationale for baseline genotypic resistance testing where prevalence warrants it. The World Health Organization maintains global surveillance of pretreatment and acquired resistance, publishes periodic reports, and has reported resistance detected in a proportion of seroconversions occurring during tenofovir-based pre-exposure prophylaxis, where infection is acquired while partial drug pressure is present.

Clinically, resistance is suspected when viral load rebounds on treatment or fails to suppress within the expected interval. Adherence, drug interactions and dosing should be reviewed first, since these explain most virological failure. Genotypic resistance testing, performed while the patient remains on the failing regimen, identifies the substitutions present and guides the construction of a new regimen containing agents to which the virus remains fully susceptible. Regimens with a high genetic barrier are preferred to reduce the likelihood of further resistance.

Antiretroviral resistance is relevant to clinical management only and has no bearing on the efficacy of cleaning, disinfection or sterilisation processes applied to reusable medical devices. Resistance substitutions alter the interaction of small-molecule drugs with viral enzymes; they confer no tolerance of detergents, oxidising or alkylating disinfectants, alcohol or moist heat, and they do not alter the lipid envelope whose disruption is the basis of rapid inactivation. A patient with multidrug-resistant HIV requires no variation to standard precautions or to reprocessing practice, and no reprocessing parameter, cycle or handling arrangement should be altered on the basis of a resistance result.