SARS-CoV-2

Associated infections

• COVID-19
• Viral pneumonia and acute respiratory distress syndrome
• Post-COVID-19 condition (long COVID)
• Multisystem inflammatory syndrome (in children and adults)
• Healthcare-associated respiratory infection

Transmission route

The principal mode of transmission is inhalation of, or mucosal deposition of, respiratory particles carrying infectious virus, generated when an infected person breathes, speaks, coughs or sneezes. These particles span a continuum of sizes; larger ones settle quickly and deposit on nearby surfaces and mucous membranes, while smaller ones remain suspended and can accumulate in indoor air. Risk is accordingly greatest at close range and in poorly ventilated indoor spaces, and is reduced by ventilation, air filtration, source control with masks and respiratory protection appropriate to the exposure. Infectiousness begins shortly before symptom onset and peaks around the first days of illness, which is why symptom-based exclusion alone does not prevent all transmission and why presymptomatic and asymptomatic transmission has been a persistent feature of the pandemic.

Transmission via contaminated surfaces is possible but the relative contribution of fomites is low compared with direct contact, droplet and airborne routes, and is further reduced by routine cleaning and hand hygiene. Quantitative risk assessments have consistently estimated the probability of infection from a single contaminated surface contact as low in community settings, and the enveloped structure of the virus makes it susceptible to routine detergents and disinfectants. This does not make surface cleaning unnecessary, but it does mean that intensified surface disinfection is not a substitute for ventilation and respiratory protection.

Viral RNA is frequently detected in wastewater and is used for community surveillance, since infected people shed RNA in faeces regardless of respiratory symptoms and wastewater sampling therefore provides an unbiased population-level signal. The presence of RNA does not equate to infectious virus. Attempts to recover viable virus from wastewater have generally been unsuccessful, and there is no clear evidence of person-to-person transmission of SARS-CoV-2 via wastewater or drinking water. Faecal-oral transmission has not been established as a meaningful route, and conventional water and wastewater treatment processes inactivate enveloped viruses efficiently. Wastewater detection should therefore be understood as an epidemiological surveillance tool and not as evidence of a waterborne transmission hazard.

Relevance in endoscopy and reprocessing

SARS-CoV-2 is relevant to endoscopy, CSD and dental services principally as an occupational and patient-safety respiratory hazard rather than as a device-borne one. Upper gastrointestinal endoscopy and bronchoscopy involve direct instrumentation of the airway or upper aerodigestive tract and are associated with coughing and gagging; most dental procedures using high-speed handpieces, air-water syringes and ultrasonic scalers generate substantial aerosol. These are the procedures for which additional precautions are justified, and the relevant controls are ventilation, respiratory protection and patient screening rather than variation of the reprocessing process.

The practical measures are patient screening and appropriate scheduling or deferral of elective procedures for symptomatic or recently diagnosed patients; assessment of room ventilation and air changes, with consideration of portable filtration where fixed ventilation is limited; a defined interval between cases in aerosol-generating settings; respiratory and hand hygiene supported by accessible facilities; and appropriate respiratory protective equipment for staff performing or assisting with aerosol-generating procedures, comprising a fit-tested particulate respirator with eye protection, gown and gloves rather than a surgical mask alone. Rubber dam use and high-volume evacuation reduce aerosol in dental settings. Routine environmental cleaning of high-touch surfaces, staff exclusion while symptomatic and current staff vaccination complete the control set. Precautions should be applied on the basis of the procedure and the epidemiological context rather than reflexively, and should be scaled back as community transmission and the vulnerability of the patient cohort permit.

Device reprocessing requires no modification for SARS-CoV-2. The virus is an enveloped respiratory virus readily inactivated by the detergents and high-level disinfectants already validated for flexible endoscopes and by the thermal and chemical sterilisation processes used in CSD, and the existing process carries a wide margin of safety against it. No extended cycle, additional agent or altered parameter is warranted, and any such variation should be resisted as it introduces risk of device damage and process deviation without benefit. Where a reprocessing failure is identified in a device used on a patient with confirmed COVID-19, the device should be quarantined at the point the failure is recognised, the reprocessing and traceability records for the affected period retrieved, and the reprocessing record audited against AS 5369:2023 and the manufacturer's instructions for use, with the incident managed under the facility's reprocessing-failure and clinical risk assessment protocol. In practice the clinical significance of such a failure will usually rest on the bacterial and bloodborne virus risk rather than on SARS-CoV-2, but the same quarantine and audit process applies.

Interpreting a detection

SARS-CoV-2 is not a rinse-water surveillance target. Routine water quality monitoring in endoscopy, CSD and dental facilities under AS/NZS 5369 is directed at organisms capable of colonising the water system and recontaminating a reprocessed device at the final rinse, principally Pseudomonas aeruginosa and other Gram-negative water organisms, non-tuberculous mycobacteria and Legionella species, with total viable count, conductivity and endotoxin used as indicators of treatment performance and system condition. A labile enveloped respiratory virus that cannot replicate outside host cells and is degraded by surfactants and by conventional water treatment has no place in that panel, and no accredited routine water test reports it. The widespread familiarity with wastewater surveillance for SARS-CoV-2 should not be read across to healthcare rinse water; the two activities have entirely different purposes, matrices and interpretive frameworks.

Where SARS-CoV-2 RNA is reported on a facility water or rinse-water sample, the result should be interpreted as a probable sampling or laboratory artefact. Nucleic acid amplification is extremely sensitive and detects non-viable fragments, and the laboratories performing these assays have handled very large volumes of clinical respiratory specimens, quantified control material and synthetic template. Carryover from clinical specimen handling, contamination of sampling equipment or containers, and amplicon contamination of reagents, pipettes and work surfaces are all far more plausible explanations than a contaminated water system. A positive result carries no implication of infectivity and no implication that any patient or staff member is at risk from the water.

Resolution should proceed through the laboratory before any action is taken on the water system. Confirm sample identity and matrix first: verify the chain of custody, the sample point identifier, the collection date and time, the container type and the labelling, and confirm that water rather than a misrouted clinical specimen was received and tested. Then establish whether the assay was validated for environmental matrices, since these assays are validated on respiratory specimens and their extraction efficiency, internal control behaviour and inhibition profile in a low-biomass water matrix are undefined; review the extraction blank and no-template control, note the cycle threshold value, since a high value on a single target is typical of contamination rather than true positivity, and check the sample's position in the run relative to high-titre specimens. Resample the same point using fresh, unopened consumables and a separate sampling kit, and split the resample between two laboratories where practicable. Finally, escalate to laboratory quality management rather than to the water safety group, since the fault to be investigated lies in specimen handling, workflow segregation and contamination control. The water safety group should be informed for completeness but should not initiate flushing, chemical disinfection, filter replacement or system shutdown, and the result should not be logged as a water quality exceedance or trended against the facility's rinse-water data. Management of SARS-CoV-2 at the facility remains an infection-control matter, addressed through screening, ventilation, respiratory protection, environmental cleaning and staff policy.