FDA Authorizes First Multiplex PCR Assay for HSV, VZV, and Mpox Skin Lesions

According to a new announcement from Seegene, Inc, the FDA has granted Emergency Use Authorization (EUA) for its Allplex HSV-1&2/VZV/MPXV Assay, described as the first multiplex PCR test designed to support differential diagnosis of viral causes of ulcerative skin lesions in the US market, with the ability to simultaneously detect and differentiate herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), varicella-zoster virus (VZV), and mpox virus (MPXV clades I/II and clade II) from a single clinical sample.¹

HSV-1, HSV-2, VZV, and MPXV all produce vesicular, pustular, or ulcerative skin lesions with overlapping clinical presentations, making visual differentiation unreliable. Single-pathogen molecular testing requires separate orders and samples for each suspected pathogen, creating a diagnostic gap when the causative virus is not among those targeted. The EUA positions the Allplex assay as a solution for clinicians encountering undifferentiated skin lesion presentations in settings where mpox, genital herpes, and herpes zoster may be in the differential.

“Seegene’s high-multiplex PCR technologies have been widely utilized across global markets,” Jun Kim, CEO of Seegene USA, said in a statement.¹ “This authorization marks an important step in bringing those capabilities more fully into the US market through Seegene USA, enabling the development of locally relevant multiplex diagnostic products.”

Allplex HSV-1&2/VZV/MPXV Assay design and clinical validation data

The Allplex HSV-1&2/VZV/MPXV Assay was developed end-to-end at Seegene USA using three proprietary high-multiplex PCR technologies: Dual Priming Oligonucleotide (DPO), which improves specificity in complex multiplex reactions; Tagging Oligonucleotide Cleavage and Extension (TOCE), which enables simultaneous detection of multiple targets at distinct temperature channels; and Multiple Detection Temperatures (MuDT), which allows individual analyte identification within a single fluorescence channel.¹ The assay was built using Seegene's automated Seegene Digitalized Development System platform, designed to maintain sensitivity and specificity across high-multiplex configurations.

In a poster presented at the 2024 Clinical Virology Symposium, researchers evaluated 966 samples previously reported as negative by single-pathogen molecular testing methods.¹ The multiplex PCR approach identified HSV, VZV, or MPXV clade I/II in 54 of those 966 samples, a 5.6% rate of detection in specimens considered negative by the existing testing paradigm, underscoring the diagnostic gap created by single-target testing.

Clinical implications of multiplex differential diagnosis for vesicular skin lesions

The authorization is clinically relevant against the backdrop of ongoing mpox transmission in the United States. MPXV clade IIb has circulated in the US since the 2022 global outbreak, and clade I has been documented in travelers and sporadic domestic cases in subsequent years.² The clinical overlap between mpox lesions and HSV or VZV reactivation is a documented source of misdiagnosis, particularly in HIV-positive patients and other immunocompromised individuals where all three infections carry significant morbidity.

For infection preventionists and ID clinicians managing patients with ulcerative genital or cutaneous lesions, the assay's ability to simultaneously rule in or rule out HSV-1, HSV-2, VZV, and MPXV in a single run addresses a workflow inefficiency with direct clinical and public health consequences.¹ A patient presenting with a vesiculopustular rash currently requires sequential testing with separate collection swabs and test orders if the treating clinician suspects more than one viral etiology. Single-tube multiplex testing compresses process and may accelerate isolation decisions, antiviral initiation, and contact notification.

Sensitivity and specificity data from the EUA validation studies were not disclosed in the press release. Clinicians and laboratory directors should consult the FDA EUA summary and the Allplex assay’s instructions for use for analytical performance characteristics before clinical implementation.

Seegene stated the EUA also advances the company’s Technology Sharing Initiative, a program supporting regional partners in developing and manufacturing multiplex molecular tests tailored to local diagnostic needs globally.¹

References

1. Seegene, Inc. Seegene USA receives FDA emergency use authorization for multiplex PCR assay, advancing differential diagnosis of HSV-1&2, VZV, and monkeypox virus for ulcerative skin lesions. Published July 21, 2026. Accessed July 21, 2026. https://www.prnewswire.com/news-releases/seegene-usa-receives-fda-emergency-use-authorization-for-multiplex-pcr-assay-advancing-differential-diagnosis-of-hsv-12-vzv-and-monkeypox-virus-for-ulcerative-skin-lesions-302830847.html

2. Centers for Disease Control and Prevention. Mpox in the United States. Updated 2026. Accessed July 21, 2026. https://www.cdc.gov/mpox/situation-summary/index.html