Presented at APIC 2026, Whole Genome Sequencing Helps Investigators Trace Pseudo-Outbreak to Contaminated Ultrasound Gel

A collaborative investigation involving hospital infection preventionists (IPs), state public health officials, and international partners demonstrates how modern genomic tools can help uncover the source of unusual health care-associated infection clusters.

Presented at the Association for Professionals in Infection Prevention and Epidemiology Annual Conference and Exposition held from June 15 to 17, 2026, in Nashville, Tennessee, Ellie Carter, CLS, MPH, CIC, an IP at Abbott Northwestern Hospital, part of Allina Health, Jennifer L. Dale, PhD, and Paula Snippes Vagnone, MT(ASCP), both with Minnesota Department of Health (MDH), presented findings from a study titled "Echoes of Contamination: Unveiling a Pseudo-Outbreak Using Classic and Modern Epidemiology." The investigation traced an apparent outbreak of Paraburkholderia fungorum bloodstream infections to contaminated nonsterile ultrasound gel, ultimately contributing to a national patient safety alert.

Whole genome sequencing (WGS) has become an increasingly valuable tool in outbreak investigations, allowing epidemiologists to determine whether organisms identified in different patients are genetically related. Carter and colleagues highlighted how WGS helped connect what initially appeared to be isolated cases across multiple facilities and even multiple countries.

The investigation began in August 2024, when the MDH identified an unusual increase in blood cultures positive for P fungorum, a bacterium rarely encountered in clinical practice.

According to the authors, WGS revealed that isolates from affected patients were "closely related," suggesting a common source rather than unrelated sporadic infections. Investigators collaborated with health care facilities throughout the US and internationally to compare genomic data and search for potential links.

A critical breakthrough occurred when a colleague in Israel isolated P fungorum from a bottle of non-sterile ultrasound gel. Around the same time, MDH requested testing of ultrasound gel products used within the Allina Health system after reviewing isolates that had been submitted as part of routine surveillance requirements.

"A local epidemiological link was established when the MDH lab isolated P fungorum from one submitted bottle of nonsterile ultrasound gel," Carter and colleagues reported. The organism recovered from the gel was "closely related by whole genome sequencing to the isolates identified in the outbreak."

Additional chart reviews conducted by infection prevention teams revealed another important connection. Every patient in the health system identified with P fungorum bacteremia had undergone placement of a peripheral intravenous catheter in an emergency department setting.

The findings aligned with growing concerns regarding the use of nonsterile ultrasound gel during percutaneous procedures.

After investigators shared their findings with the CDC, the agency issued a national alert in May 2025 recommending the exclusive use of sterile ultrasound gel before and during percutaneous procedures. In response, Allina Health implemented a systemwide safety advisory reminding staff to use sterile ultrasound gel whenever skin is punctured.

The authors noted that the event represented a pseudo-outbreak rather than a traditional infectious disease outbreak because contamination of a medical product, rather than patient-to-patient transmission, was responsible for the cluster of cases.

"This investigation highlights the importance of whole genome sequencing to inform genomic epidemiology and the importance of clinical and public health collaboration to identify outbreaks," the authors wrote.

The case also underscores the continued need for education on appropriate ultrasound gel selection and reinforces the role of genomic epidemiology in complementing traditional infection prevention investigations. As health care-associated infection surveillance becomes increasingly sophisticated, investigators say combining classic epidemiology with advanced molecular techniques will remain essential for identifying hidden sources of contamination and protecting patients from preventable harm.