Diasorin Continues to Support Diagnostic Stewardship for Respiratory Seasonal Testing with the Simplexa^® COVID-19 / Flu A/B & RSV Direct

In the 2025–2026 respiratory season, rapid and accurate testing for the common respiratory viruses remain of the utmost importance. Given the overlapping symptoms across COVID-19, influenza A/B, and respiratory syncytial virus (RSV), accurately distinguishing between these infections is essential for timely treatment, appropriate isolation measures, and ensuring effective patient care.

Our next generation Simplexa^® COVID-19 / Flu A/B & RSV Direct assay was FDA 510(k) cleared in October 2025. This assay powered by new chemistry for faster results and additional target detection on the proven LIAISON^® MDX instrument. Designed to detect and differentiate SARS-CoV-2, influenza A, influenza B, and RSV directly from both nasopharyngeal swabs and anterior nasal swabs, this assay provides critical diagnostic support in a single streamlined test.

Why differentiation matters

COVID-19, influenza A, influenza B, and RSV present with similar respiratory symptoms—including fever, cough, congestion, and fatigue—but require different clinical responses. Accurate diagnosis supports appropriate use of antivirals like Paxlovid for COVID-19 or oseltamivir for influenza and timely supportive care for RSV, especially in pediatric and elderly patients, and effective isolation to reduce transmission.

According to the CDC, seasonal influenza causes millions of illnesses annually in the US, with estimates between 610,000 and 1.3 million hospitalization in 2024. RSV leads to approximately 58,000 hospitalizations in children under 5 and up to 160,000 hospitalizations in adults 65 and older.^1,2

Moreover, co-infections with multiple respiratory viruses are increasingly observed, especially in high-risk populations, highlighting the need for multiplex assays that deliver accurate, actionable results.

The changing seasonality of respiratory viruses

Traditionally, influenza and RSV peak in the fall and winter months, shaping the standard respiratory testing window. COVID-19 can demonstrate two annual peaks, one in the summer and the other during the typical respiratory season with flu and RSV.³

This non-overlapping pattern reinforces the importance of offering flexible testing options year-round, including standalone SARS-CoV-2 testing when SARS-CoV-2 is circulating outside of the broader respiratory virus season. A fixed testing menu is no longer sufficient; labs need an adaptable approach. A combined differential‑diagnosis approach is essential for accurate seasonal testing.

Tailored testing for diverse populations

The pediatric population presents unique diagnostic challenges. Along with a high burden of RSV, children are also vulnerable to Bordetella pertussis (B. pertussis) and Bordetella parapertussis (B. parapertussis), which can cause whooping cough: a severe, potentially life-threatening illness in infants. Accurate identification is essential not only for treatment, but also for public health measures like contact tracing and vaccination reinforcement.

Diasorin’s Simplexa^® Bordetella Direct assay allows for rapid differentiation of B. pertussis and B. parapertussis, delivering critical information to guide course of treatment.

Similarly, Group A Streptococcus (S. pyogenes), a leading cause of sore throat in children, can be rapidly diagnosed using the Simplexa^® Group A Strep Direct assay, reducing the misuse of antibiotics and expediting treatment decisions.

A respiratory menu built for real-world needs

We recognize that respiratory diagnostics must be flexible, scalable, and targeted to meet diverse clinical scenarios. Therefore, Diasorin has built a comprehensive portfolio of molecular assays to support both syndromic and targeted respiratory pathogen diagnostics, allowing labs to choose the right test based on clinical presentation, patient age, immune status and seasonality.

Diasorin’s full FDA-cleared respiratory menu outlined below including key features for adaptable laboratory testing algorithms:

• Simplexa^® COVID-19 / Flu A/B & RSV Direct assay: Multiplex detection and differentiation of common seasonal viruses in an efficient and direct sample-to-answer workflow in 50 minutes.
• Simplexa^® COVID-19 Direct assay: A proven tool during the pandemic, focused on simple utility and high-performance solution for standalone COVID-19 testing during summer season peaks.
• Simplexa^® Flu A/B & RSV Direct Gen II: Sample to answer influenza A/B & RSV detection and differentiation with broad strain coverage.
• Simplexa^® Bordetella Direct assay: Differentiates key Bordetella species in pertussis-suspected patients in about 1 hour, an ideal test for outbreak-related testing.
• Simplexa^® Group A Strep Direct assay: Fast and accurate detection of Group A Streptococcus in about an hour.
• LIAISON PLEX^® Respiratory Flex Assay: A 21-target syndromic panel for comprehensive and one-of-a-kind customizable Flex™ Testing in complex or immunocompromised cases.
• LIAISON NES^® FLU A/B, RSV & COVID-19 Assay: a point of care, real-time RT-PCR test used on the patented LIAISON NES® instrument to detect influenza A, influenza B, RSV, and SARS-CoV-2 viruses in dry nasal swabs in ~15 min.

Whether used as standalone assays or as part of a customized testing algorithm, these tools empower laboratories to optimize diagnostic workflows and deliver actionable results tailored to clinical need.

Conclusion

As respiratory viruses continue to circulate and evolve, laboratories must be equipped with diagnostic tools that are accurate, efficient, and flexible. The launch of the Simplexa^® COVID-19 / Flu A/B & RSV Direct assay enhances our commitment to meeting those demands, offering precision testing that helps clinicians deliver better care faster.

With Diasorin’s complete respiratory portfolio, labs can build smarter testing strategies to meet the needs of all seasons, all patients, and all levels of care.

Learn more about the latest addition to the Simplexa portfolio.