A Sensitive and Specific One-step TaqMan RT-qPCR Assay for Rapid Detection of Enterovirus C99

Viruses that infect the gut are a constant, invisible presence in our world. Among the most common of these are enteroviruses, a large family of tiny, non-enveloped particles that carry their genetic instructions on a single strand of RNA. While many of these viruses cause only mild illness, some can lead to severe neurological problems or paralysis. Because these viruses mutate rapidly and often swap genetic material with one another, they are constantly evolving, making them difficult to track. Within this vast family, a specific group known as Enterovirus C contains several types, including the well-known poliovirus and a newer, emerging member called Enterovirus C99. This specific virus has been found in humans and other animals across many countries, raising concerns about its ability to jump between species and spread silently through the environment. Detecting it quickly and accurately is crucial for public health, yet the tools currently available to find it are often slow, prone to errors, and unable to distinguish this specific virus from its many cousins without extensive and time-consuming follow-up work.

To solve this problem, a team of researchers from Hainan University and the Guangdong Provincial Center for Disease Control and Prevention set out to build a better way to find Enterovirus C99. They focused on a specific part of the virus's genetic code, a region within a gene called VP1 that acts like a unique fingerprint for this particular virus type. Using this target, they designed a new test that combines the process of copying genetic material and measuring it into a single, streamlined step. This method, known as a one-step TaqMan RT-qPCR assay, works by using a special probe that lights up only when it finds the exact genetic sequence of Enterovirus C99. Unlike older methods that require opening the test tube after the reaction to look for results, this new approach detects the virus in real time as the reaction happens, keeping the sample sealed and reducing the risk of contamination.

The researchers first had to fine-tune the ingredients of their test to ensure it worked perfectly. They experimented with different amounts of the chemical primers and probes that guide the reaction, eventually settling on a specific combination that produced the strongest and most reliable signal. Once optimized, they tested the new method against a wide variety of other enteroviruses, including Coxsackievirus, Echovirus, and Poliovirus, to see if it would mistake them for Enterovirus C99. The results were clear: the test only lit up when Enterovirus C99 was present. It ignored every other virus they threw at it, proving that the new tool is highly specific and will not generate false alarms.

Sensitivity was the next major hurdle. The team wanted to know the smallest amount of virus the test could detect. They created a series of samples with decreasing amounts of the virus's genetic material, going down to incredibly tiny concentrations. The new test successfully identified the virus even when there were approximately 0.366 copies of the genetic material per microliter of liquid. In direct comparison, the older, conventional method used in laboratories could only see the virus when the concentration was one hundred times higher. This means the new assay is a hundred times more sensitive, capable of spotting the virus when it is present in very low numbers that would otherwise go unnoticed. The test also proved to be extremely consistent; when the researchers ran the same sample multiple times, the results varied by less than two percent, showing that the method is stable and reliable.

To see how the test performed in the real world, the researchers applied it to ninety-two wastewater samples collected from sewage treatment plants across Guangdong Province between 2024 and 2025. These samples had already been flagged as containing some type of enterovirus, but the specific type was unknown. The new test scanned all ninety-two samples and found one that contained Enterovirus C99. This single positive result represented a detection rate of just over one percent. To be absolutely certain, the researchers took that positive sample and ran it through a standard sequencing process, which reads the genetic code letter by letter. The sequence confirmed that the virus was indeed Enterovirus C99, matching the result from the new rapid test perfectly. The entire process, from extracting the genetic material to getting a result, took about two hours, a significant improvement over the four to six hours required by traditional methods that involve multiple steps and gel electrophoresis.

This work demonstrates that a fast, precise, and highly sensitive tool for detecting Enterovirus C99 is now available. By targeting a specific genetic signature and using a real-time detection system, the researchers have created a method that can identify this emerging virus quickly and without confusion from other similar viruses. While the study found only one positive sample in the wastewater tested, the ability to detect the virus at such low levels and with such speed provides a powerful new capability for monitoring its spread. This tool offers public health officials a way to track the virus in the environment and potentially catch outbreaks earlier, helping to manage the risks posed by this evolving pathogen.