Ultrasound feels like the safe imaging modality. No radiation, no contrast dye, no needle by default — a wand, a squirt of gel, a picture. That reputation is exactly why its infection risks are so easy to underrate. The probe is a reusable medical device that touches patient after patient, sometimes across intact skin, sometimes across a mucous membrane, and sometimes at the edge of a percutaneous procedure where the skin barrier is about to be broken. Each of those exams carries a different level of risk, and reprocessing that treats them all the same is where transmission quietly happens. Two guidance documents released in close succession — the Society for Maternal-Fetal Medicine's 2026 update on reducing infection during ultrasound examination, and the American Institute of Ultrasound in Medicine's 2025 revision of its transducer and coupling-gel guidelines — have put that mismatch back in the spotlight. Neither is a dramatic reversal. Both are a reminder to do the ordinary things well and to match the layer to the exam.

What actually changed in 2026

The framework underneath both documents is decades old and worth restating, because it is where most reprocessing errors begin. It is the Spaulding classification, and it sorts every reusable device into three tiers by what it contacts. Applied to ultrasound, the sort is simple. A transducer that touches only intact skin — the abdominal probe on a pregnancy scan, the linear probe on a shoulder — is noncritical, and needs cleaning followed by low-level disinfection between patients. A transducer that touches mucous membranes or non-intact skin — transvaginal, transrectal, transesophageal — is semicritical, and requires high-level disinfection (HLD) plus a single-use cover every time. A transducer used to enter sterile tissue during a percutaneous procedure is critical, and calls for a sterile single-use barrier with sterility dictated by the procedure. One wand, potentially three different obligations depending on the exam in front of you.

What the newer documents sharpen is not the categories but the follow-through. The AIUM's 2025 revision states plainly that "internal transducers require routine mandatory high-level disinfection," and pairs that with a detail clinics skip under time pressure: transducers must be thoroughly dried before HLD, because "wet surfaces dilute the disinfectant." It also folds coupling gel into the same infection-control frame rather than treating it as an afterthought. The SMFM's 2026 statement, in turn, keeps the field's most pointed correction in place — that not every high-level disinfectant is equal against every pathogen, a point that matters enormously for the semicritical probes SMFM's members use most.

The gel nobody suspects

Start with the part of the workflow that looks least like a medical device: the gel. It is inert-looking, cheap, and dispensed by the liter, which is precisely why it has repeatedly turned out to be the weak link. Ultrasound coupling gel is water-based and can support bacterial growth, and the pathogens that thrive in it — Burkholderia, Pseudomonas, and their relatives — are opportunists that do real damage once they reach a bloodstream or a surgical field.

The definitive warning is not hypothetical. Between May and September 2021, the CDC documented an outbreak of Burkholderia stabilis infections across ten states, ultimately counting 119 patients, with 14 deaths among those whose outcomes were known — a 14% case-fatality rate. The common thread was a specific lot of nonsterile, multiuse ultrasound gel, later recalled, and the exams that mattered were invasive: 94% of case-patients had undergone an ultrasound-guided percutaneous procedure, and the large majority of infections were bloodstream infections. This was not a stain on a tabletop. It was contaminated gel introduced at the moment the skin barrier was crossed.

Both the CDC and the ultrasound societies drew the same line from that event. As the CDC put it, "only single-use, sterile ultrasound gel packets should be used for ultrasonography in anticipation of, preparation for, or during percutaneous procedures." The AIUM's 2025 revision extends the sterile-gel requirement further — to "all invasive procedures that pass a device through tissue" and to "all ultrasound examinations performed on neonates," whose defenses leave no margin for a contaminated coupling agent. For routine external scans on intact skin, a multiuse container remains acceptable, but only with discipline: do not top off or refill bottles, discard and replace them when empty, keep the dispensing tip from touching patients or equipment, and warm gel only with dry heat — never by immersing a bottle in a water bath, which is its own contamination route.

Why "high-level disinfection" is not a single thing

For the semicritical probes — the transvaginal and transrectal transducers central to obstetric and gynecologic imaging — high-level disinfection between patients is not optional, and a single-use cover does not replace it. Covers fail more often than clinicians assume; the AIUM and SMFM both treat the cover as an added barrier, not the disinfection step. But the more consequential nuance is that "high-level disinfection" names a performance category, not a guarantee of efficacy against every organism a probe might carry.

The clearest example is human papillomavirus. HPV is a small, non-enveloped, notably tough virus, and the SMFM has been explicit that some widely used HLD chemistries underperform against it. The society's statement notes that "glutaraldehyde, orthophthalaldehyde, phenols, and isopropyl alcohol have virtually no efficacy against the human papillomavirus" — a striking claim, because glutaraldehyde and OPA are exactly the agents many facilities assume are the gold standard. The chemistries the guidance points toward instead are the oxidizing ones: hydrogen peroxide, peracetic acid, and hypochlorite. A clinic can run a validated, FDA-cleared HLD process, follow every step, and still be using a chemistry the guidance flags as weak against a virus its patients actually carry. The lesson is not to abandon HLD; it is to choose the disinfectant with the target pathogens in mind.

Two operational details separate HLD that works from HLD that only looks like it does. The first is drying: a probe carried wet into a disinfectant dilutes it below its effective concentration, which is why the AIUM stresses thorough drying first. The second is concentration monitoring. Reusable HLD solutions weaken with each use as they are diluted and consumed, and the only way to know a solution is still above its minimum effective concentration is to test it with the manufacturer's chemical indicator before each cycle. A solution that looks fine and is a day past its titer is a documented reprocessing failure waiting for an audit to find it.

Matching SONO's ultrasound line to the three risk tiers

Reprocessing guidance is only as good as the supplies behind it, and the Spaulding tiers map cleanly onto a stocked cart. SONO carries the pieces for each layer of an ultrasound infection-control routine.

For invasive, neonatal, and near-sterile exams — Clear Image Sterile Ultrasound Gel comes as individually sealed, single-use 20-gram packets: the format the CDC and AIUM call for whenever a device passes through tissue, whenever the patient is a neonate, or whenever a multiuse bottle is a risk the exam cannot carry.

For high-level disinfection of semicritical probes — STERIS RESERT Revital-Ox High-Level Disinfectant is a hospital-grade, hydrogen-peroxide-based HLD — the oxidizing chemistry family the guidance points toward rather than away from. Pair it with RESERT R60 concentration test strips so every cycle is verified above its minimum effective concentration before a probe goes in, and the log is there when the surveyor asks. SONO is an authorized STERIS distributor, in 1 liter and 4 liter sizes with fresh stock.

For noncritical external transducers between patients — SONO Ultrasound Disinfecting Wipes are EPA-registered and formulated to be safe on transducer housings and machine surfaces — alcohol-free, so they clean and disinfect the external probe and equipment without the crazing and corrosion harsher chemistries inflict on a device you scan with all day. Always follow each product's label for the correct contact time and device compatibility.

Sterile Gel Packets RESERT HLD Probe Wipes

A reprocessing routine that follows the risk

The point of the guidance is not more work on every exam — it is the right work on each one. A routine that sorts by Spaulding tier at the moment of the scan, rather than defaulting to a single habit, is both safer and, on the noncritical majority, faster.

The bottom line for the service line

Nothing in the 2025 and 2026 guidance asks a busy ultrasound service to reinvent its workflow. It asks for something harder in its own way: to stop treating every exam the same. The abdominal scan and the transvaginal scan and the ultrasound-guided line placement are three different infection-control problems sharing one machine, and the guidance simply insists that the gel, the cover, and the disinfectant each rise to meet the exam actually in front of the sonographer. Choose sterile single-use gel when the barrier is broken or the patient is a neonate. Reach for an oxidizing high-level disinfectant and verify its concentration before high-level disinfecting a semicritical probe. Clean and disinfect the external probe between every patient with a product that will not corrode it. None of it is glamorous, and all of it is the difference between an imaging study and a bloodstream infection. The 2021 outbreak is the reminder of what the stakes are; the 2026 guidance is the map for not repeating it.